METHODS FOR PRODUCING AMMONIA FROM DINITROGEN USING ELECTROCHEMICAL DEVICES HAVING ATOMIC METAL ON GRAPHENE FOR ELECTROCHEMISTRY CROSS-REFERENCE TO RELATED PATENT APPLICATIONS [0001] This application claims priority to U.S. Patent Appl. Serial No. 63/078,023, filed September 14, 2020, entitled “Methods For Producing Ammonia From Dinitrogen Using Electrochemical Devices Having Atomic Metal On Graphene For Electrochemistry,” which patent application is commonly owned by the owner of the present invention. This patent application is incorporated herein in its entirety. TECHNICAL FIELD [0002] The present invention relates methods for the production ammonia, and more particularly methods for the production of ammonia from dinitrogen using electrochemical devices having atomic metal on graphene for electrochemistry. BACKGROUND [0003] Nitrogen, more precisely referred to as dinitrogen (N ₂ ), as the one of the most abundant elements, is essential for the growth, reproduction and biosynthesis in both plants and animals. It constitutes the skeletons of proteins, nucleotides and other ubiquitous biological molecules that comprise the hereditary material and life’s blueprint for all cells and living organism. [Gruber 2008]. Although molecular dinitrogen is the major component on earth that comprises ~78% of the Earth's atmosphere, the covalent N≡N triple bond with high bond energy of 940.95 kJ mol ^-1 makes it one of the most stable molecules in chemistry and strongly limits its reactivity. [MacKay 2004]. [0004] Due to the increase in human population, human-made nitrogen-containing fertilizers are crucial for the production of sufficient food to support approximately half of the global population. [Smil 1999]. To date, the activation and conversion of molecular N ₂ into NH ₃ relies heavily on the energy-intensive Haber–Bosch process that requires a high temperature of 350– y50 °C and pressure of 350 atm. [Erisman 2008; Kandmir 2013]. [0005] Despite its appealing capacity, a search for processes that do not use the harsh conditions and high energy consumption in Haber–Bosch process has been ongoing for decades. [Kitano 2015]. Taken together, the Haber–Bosch process for NH ₃ synthesis currently results in 1–2% of the world’s annual energy supply consumption. [Galloway 2008]. Therefore, it is, and remains, desirable to find a more sustainable and economical process for N ₂ fixation and NH ₃ production, and desirable to find a process that could more easily provide for simple local generation plants rather than the complex Haber–Bosch process plants. [Chatt 1978]. [0006] In nature, the fixation of N ₂ to NH ₃ is a fundamental process occurring in microorganisms such as bacteria via the nitrogenase enzymes, in which NH ₃ is synthesized from atmospheric N ₂ , H ₂ O, transferred electrons and energy provided by adenosine triphosphate (ATP) on a MoFe-cofactor under ambient conditions (N ₂ + 6H ⁺ + nMg-ATP + 6e ^– (nitrogenase) → 2NH ₃ + nMg-ADP + nPi). [Hoffman 2014; Einsle 2002]. Heuristically, the mechanism of the nitrogen reduction reaction (NRR) in nitrogenase has recently inspired the investigation of alternative electrochemical processes to directly reduce N ₂ to NH ₃ at room temperature and pressure. [Singh 2018; Deng 2018; Milton 2016]. Further, the exploration of electrochemical N ₂ conversion into NH ₃ through renewable electricity would promote a sustainable and economical route for NH ₃ production, thereby satisfying the present demand for fertilizer and the future desire of energy carriers in the hydrogen economy. [Montoya 2015]. [0007] Based on direct N ₂ reduction via nitrogenase, for decades, researchers sought inspiration to explore the ability of synthetic metal-cored catalytic sites to activate N ₂ under ambient conditions. However, up to now, few strategies have been developed to optimize the NH ₃ production rate or to alleviate the thermodynamic requirements using different electrocatalytic approaches. A series of transition-metal based (e.g., Fe, Ru, and Mo) molecular catalysts have been designed and synthesized in order to achieve homogeneous catalytic activity for NRR. [Yandulov 2003; Rodriguez 2011; Hidai 1995]. Even though these molecular catalysts sometime exhibit intriguing activities, the poor durability, low Faradaic efficiencies and weak attachment and electron transfer from catalyst to electrodes often limit their practical applications. [Suryanto 2018]. [0008] Therefore, single-atom catalysts (SAC), which are made of isolated metal atoms anchored through the binding sites of solid supports, could be promising candidates to established a bridge between molecular homogenous catalysts and heterogeneous catalysts, delivering an improved electrochemical NRR performance upon a highly conductive substrate. Whereas noble metals-based SACs including Au, Ru, and Pd show high catalytic activity for NH ₃ electrosynthesis, the high cost and scarcity of noble metals impose a burden on their widespread application. [Liu 2019; Shi 2017; Tao 2019]. NRR research has thus shifted to the investigation and development of noble-metal-free alternatives. Due to its relative rich earth- abundance and diversified d-orbital electron configurations, Mo has emerged as an attractive transition metal for designing active sites in the catalytic reduction of N ₂ to NH ₃ . [Ling 2018]. [0009] Generally, there are three main challenges in achieving a high Faradaic efficiency for NRR on traditional heterogenous catalysts: (1) most heterogenous catalysts, either metal or non-metal-based, have a weak-binding adsorption for molecular N ₂ , limiting the first activation step of N ₂ through M*-N ₂ ; (2) large overpotential is usually found to be essential for NRR on heterogenous catalysts in order to protonate the intermediate species and make the reaction kinetically feasible; and (3) the competing hydrogen evolution reaction (HER), leading to a deteriorated Faradaic efficiency for NRR, could easily occur with the large overpotential for traditional metal-based heterogenous catalysts. Accordingly, one of the major challenges in optimizing electrocatalytic NRR performances is to discover an efficient electrocatalytic system that can reduce the overpotential (near the thermodynamically determined reduction potential) and increase the selectivity (also referred as Faradaic efficiency, FE) of NH ₃ synthesis during electrolysis. This must be done while also minimizing the competitive hydrogen evolution reaction (HER). [0010] Only a few bulk metals (e.g., Re, Sc, Y, and Zr) are capable of suppressing the HER at low potentials but they still lack effective activities to obtain acceptable NRR performances. [Singh 2011; She 2017; Montoya 2015]. Therefore, single-atom catalysts (SAC), which established a bridge between molecular homogenous catalysts and heterogenous catalysts, could be promising candidates to combine the advantages and avoid the disadvantages of molecular and heterogenous catalysts, delivering an improved electrochemical NRR performance under ambient conditions. [Ling 2018; Yang 2013; Wang 2018]. SUMMARY OF THE INVENTION [0011] The present invention relates methods for the production of ammonia from dinitrogen using electrochemical devices having atomic metal on graphene for electrochemistry. It has been discovered that by anchoring atomic Mo catalytic sites on a holey nitrogen-doped graphene framework (Mo/HNG), this leads to enhanced performance of N ₂ electrochemical reduction to NH ₄ ⁺ /NH ₃ with high selectivity under ambient conditions. Holey nitrogen-doped graphene (HNG), with a continuous porous skeleton and abundant edges containing nitrogen- coordination sites, can be prepared through an activation method (such as a convenient potassium salt assisted activation method). The HNG can be used as the substrate for the Mo- atom loading sites. For instance, at -0.05 V versus reversible hydrogen electrode (RHE) in 0.05 M H ₂ SO ₄ , Mo/HNG exhibited an excellent FE of 50.2% for NH ₃ production with partial reduction current density of 12.7 μA cm ^-2 with NH ₃ production yield rate of 2.7 μg h ^-1 mgcat ^-1 with low overpotentials. In some embodiments, the FE even reached approximately 68% for NH ₃ production with an NH ₃ partial current of 7.8 μA cm ^-2 . Moreover, Mo/HNG catalysts also held high catalytic stability toward N ₂ electrochemical reduction at different applied potentials. It is believed that the atomically dispersed Mo immobilized at the edges of HNG, along with the vacancies presented in the structure, jointly contribute to the intriguing NRR activity of Mo/HNG. [0012] In general, in one embodiment, the invention features a method that includes the step of producing holey nitrogen-doped graphene from graphene oxide. The method further includes the step of dispersion of molybdenum atoms anchoring on the holey nitrogen-doped graphene to form holey nitrogen-doped graphene (AMHG). The method further includes fabricating an electrochemical device utilizing the AMGH. The electrochemical device includes an electrode formed from the AMGH. The electrochemical device is used to convert N ₂ and water into ammonia. [0013] Implementations of the invention can include one or more of the following features: [0014] The electrochemical device can exhibit a Faradaic efficiency of at least 50% for ammonia production. [0015] The electrochemical device can exhibit a Faradaic efficiency of between 50 and 68% for ammonia production. [0016] The electrochemical device can operably have an overpotential of less than 0.37 V. [0017] The electrochemical device can operably have an overpotential of less than 0.32 V. [0018] The electrochemical device can be operable for a production rate of at least 7 μA mg ^-1 catalyst at -0.10 V versus a reversible hydrogen electrode. [0019] The electrochemical device can be operable for a production rate of between 7.8 and 12.7 μA mg ^-1 catalyst at -0.05 V versus a reversible hydrogen electrode. [0020] The electrochemical device can exhibit a Faradaic efficiency of at least 50% having an overpotential of less than 0.37 V and a production rate of at least 7 μA mg ^-1 catalyst at -0.10 V versus a reversible hydrogen electrode. [0021] The electrochemical device can exhibit a Faradaic efficiency of between 50 and 68% having an overpotential of less than 0.32 V and a production rate of between 7.8 and 12.7 μA mg ^-1 catalyst at -0.05 V versus a reversible hydrogen electrode. [0022] The dispersion step can be a homogeneous dispersion. [0023] The step of producing holey nitrogen-doped graphene from graphene oxide can include a simultaneous nitrogen-doping and potassium assisted activation method. [0024] The AMHG can receive its nitrogen-doping utilizing a nitrogen source selected from a group consisting of solid, liquid, gas or plasma phase nitrogen. [0025] The nitrogen source can be selected from a group consisting of melamine, melamine- formaldehyde resin, trimethylamine, ammonia, hydrazine, polyethylene amine and nitrogen atom discharge. [0026] The potassium assisted activation can utilize a potassium-containing compound. [0027] The potassium-containing compound can be a potassium containing salt. [0028] The potassium-containing compound can be potassium chloride or potassium acetate. [0029] The temperature of simultaneous nitrogen-doping and potassium assisted activation can be in the range between 400°C and 1200°C. [0030] The AMHG can be used in electrochemical nitrogen fixation and ammonia production. [0031] The AMHG can be in a form selected from a group consisting of solid pieces, powders, foams, thin film, and combinations thereof. [0032] The average diameter of nanopores in the AMHG can be in the range between 1 nm and 100 nm. [0033] The average diameter of the nanopores in the AMHG can be in the range between 2 nm and 10 nm. [0034] AMHG structures can be produced from the graphene oxide. [0035] A foam of the holey nitrogen-doped graphene can be produced from lyophilization of the graphene oxide. [0036] The dispersion of the molybdenum atoms in AMHG can be performed on a substrate. [0037] The substrate can be a holey nitrogen-doped graphene substrate or a nitrogen-doped graphene substrate. [0038] The method can include a wet chemistry process with molybdenum compounds as reagents. [0039] The substrate can include a material selected from a group consisting of nitrogen-doped carbons, nitrogen-doped carbon nanotubes, heteroatom-doped graphene, nitrogen-doped graphene quantum dots, nitrogen-doped carbon dots, and nitrogen-doped carbon black. [0040] The atomic dispersion of the molybdenum can be controlled on the substrate. [0041] The method can further include dispersing additional metal atoms selected from a group consisting of iron, ruthenium, cobalt, manganese, nickel, silver, gold, copper, palladium, platinum, tungsten, chromium, and combinations thereof. [0042] A solvent can be utilized to disperse the molybdenum. [0043] The solvent can be an aqueous solvent. [0044] The solvent can be a non-aqueous solvent. [0045] The electrode can be an electrode for nitrogen fixation and ammonia production. [0046] The electrode can be prepared on a periodic basis or by computer-controlled fabrication. [0047] The periodic basis can be weekly, monthly, or annually. [0048] The electrode can have added polymer or nanomaterial-based binders to disperse and attach electrocatalysts onto a surface of the electrode. [0049] The electrochemical device can have an electrochemical cell. A gas or solution-based diffusion of N ₂ can be applied in the electrochemical cell for nitrogen fixation and reduction. [0050] The electrochemical cell can be a pressurized electrochemical cell. [0051] The electrode can be a gas diffusion electrode. [0052] The electrode formed from the AMGH can be formed at room temperature and atmospheric pressure. [0053] The AMHG can prepared on a substrate including a substrate material selected from a group consisting of graphene quantum dots, segregated carbon black, carbon dots, and combinations thereof. [0054] The preparation of the AMGH on the substrate can include the substrate can mitigate aggregation of single-atom catalysts. [0055] The substrate material can include graphene quantum dots. The substrate material can mitigate aggregation of the single-atom catalysts due to there being only a few single atoms per quantum dot, which enables a higher concentration of the single-atom catalysts. [0056] The substrate material can include graphene quantum dots. The graphene quantum dots can be made from a carbon material selected from a group consisting of activated charcoal, coal, coke, saccharide-derived carbon, and combinations thereof. [0057] The substrate material can include graphene quantum dots. The graphene quantum dots can be made from a carbon material that includes oxidized activated charcoal. The graphene quantum dots can benitrogen-doped and then reduced to form nitrogen-doped graphene quantum dots. [0058] The oxidized activated charcoal can have an average diameter between 1 nm and 30 nm. The nitrogen-doped graphene quantum dots can have an average diameter between 1 nm and 30 nm. [0059] The nitrogen-doped graphene quantum dots can have an average diameter between 2 nm and 5 nm. [0060] In general, in another embodiment, the invention features a method that includes the step of producing holey nitrogen-doped graphene from graphene oxide. The method further includes the step of dispersion of transition-metal atoms anchoring on the holey nitrogen-doped graphene to form on transition-metal/HNG material. The method further includes the step of fabricating an electrochemical device utilizing the transition-metal/HNG material. The electrochemical device includes an electrode formed from the transition-metal/HNG material. The electrochemical device is used to convert N ₂ and water into ammonia. [0061] Implementations of the invention can include one or more of the following features: [0062] The electrochemical device can exhibit a Faradaic efficiency of at least 50% ammonia production. [0063] The electrochemical device can exhibit a Faradaic efficiency of between 50 and 68% for ammonia production. [0064] The electrochemical device can operably have an overpotential of less than 0.37 V. [0065] The electrochemical device can operably have an overpotential of less than 0.32 V. [0066] The electrochemical device can be operable for a production rate of at least 7 μA mg ^-1 catalyst at -0.10 V versus a reversible hydrogen electrode. [0067] The electrochemical device can be operable for a production rate of between 7.8 and 12.7 μA mg ^-1 catalyst at -0.05 V versus a reversible hydrogen electrode. [0068] The electrochemical device can exhibit a Faradaic efficiency of at least 50% having an overpotential of less than 0.37 V and a production rate of at least 7 μA mg ^-1 catalyst at -0.10 V versus a reversible hydrogen electrode. [0069] The electrochemical device can exhibit a Faradaic efficiency of between 50 and 68% having an overpotential of less than 0.32 V and a production rate of between 7.8 and 12.7 μA mg ^-1 catalyst at -0.05 V versus a reversible hydrogen electrode. [0070] The transition-metal atoms can be atoms of a transition-metal selected from the group consisting of iron, ruthenium, molybdenum, cobalt, manganese, nickel, silver, gold, copper, palladium, platinum, tungsten, chromium, and combinations thereof. [0071] The dispersion step can be a homogeneous dispersion. [0072] The electrode formed from the transition-metal/HNG material can be formed at room temperature and atmospheric pressure BRIEF DESCRIPTION OF THE DRAWINGS [0073] FIG.1A is a schematic of the process for preparation of Mo/HNG catalyst. [0074] FIG.1B shows electrode Faradaic efficiency (FE) based upon various conditions when forming electrodes utilizing the catalyst of FIG.1A. [0075] FIGS. 2A-2E show morphological characterization of the Mo/HNG catalyst. FIGS. 2A-2B are, respectively, HRTEM images of HNG-750 and NG-750 control. FIG. 2C is an HRTEM images of the Mo-HNG catalyst FIG. 2D is a representative atomic resolution HAADF-STEM image of Mo-HNG and magnified area with circled individual Mo atoms immobilized on the carbon matrix presumably at N-rich edges. FIG.2E is energy-dispersive X-ray spectroscopy (EDS) mapping spectra of Mo/HNG catalyst, C, N, and Mo are labelled. [0076] FIGS.3A-3B are SEM images of a HNG-750 sample at different magnifications. [0077] FIGS.4A-4I show XPS, XRD and Raman characterization of HNG-750 and Mo/HNG- 750. FIG.4A is a high-resolution XPS spectra of N 1s peak of HNG-750 and comparison with NG-750. FIG.4B is Raman spectra of HNG-750 and NG-750. FIG.4C is XPS survey spectra of Mo/HNG-750 catalyst and HNG-750. FIG. 4D is XRD spectra of Mo/HNG-750 catalyst and HNG-750. FIG.4E is high-resolution XPS spectra of Mo 3d peak of Mo/HNG-750. FIG. 4F is high-resolution XPS spectra of N 1s peak of Mo/HNG-750 and HNG-750. FIG.4G is k ³ -weighted EXAFS spectra of Mo/HNG, 2Mo/HNG and Mo foil (with the Mo foil transformed by 0.3). FIG.4H (with magnification shown in FIG.4I) is XANES spectra at the Mo K edge of Mo/HNG. [0078] FIG. 5A is XRD spectra (Cu Kα radiation) of HNG-750, Mo/HNG, NG-750, and Mo/NG catalysts. [0079] FIGS. 5B-5C are, respectively (a) N ₂ adsorption isotherms and (b) pore size distribution of HNG-750, Mo/HNG, NG-750, and Mo/NG. [0080] FIGS.6A-6D show electrocatalytic performance of N ₂ reduction to NH ₄ ⁺ /NH ₃ over the Mo/HNG-750 catalyst. FIG. 6A is a schematic illustration of reaction cell for NRR measurements. FIG. 6B is potential-dependent Faradaic efficiency (FE) and partial current densities of NH ₄ ⁺ /NH ₃ for NRR on Mo/HNG-750 catalysts -0.10 V to -0.60 V vs reversible hydrogen electrode (RHE), which is used as a reference electrode, in the N ₂ -saturated 0.1 M HCl solution. FIG.6C is potential-dependent Faradaic efficiency (FE) of NH ₄ ⁺ /NH ₃ for NRR on Mo/HNG-750 from different precursors and Mo-NG-750 catalysts calculated from chronoamperometric measurements at -0.10 V vs. RHE. FIG.6D is potential-dependent partial current densities of NH ₄ ⁺ /NH ₃ for NRR on Mo/HNG-750 from different precursors and Mo- NG-750 catalysts calculated from chronoamperometric measurements at -0.10 V vs. RHE. [0081] FIG.7 shows the evolution reaction in the schematic illustration of FIG.6A. [0082] FIGS. 8A-8D are Brunauer−Emmett−Teller (BET) surface analysis of HNG and Mo/HNG samples made with different potassium sources. FIG.8A is N ₂ adsorption-desorption isotherms at 77 K for HNG samples made with different potassium sources. FIG. 8B is N ₂ adsorption-desorption isotherms at 77 K for Mo/HNG samples made with different potassium sources. FIG. 8C is pore size distribution curves for HNG samples made with different potassium sources. FIG.8D is pore size distribution curves for Mo/HNG samples made with different potassium sources. [0083] FIGS.9A-9B show linear sweep voltammetry (LSV) curves of Mo/HNG under Ar and N ₂ -saturated 0.05 M H ₂ SO ₄ electrolyte. [0084] FIGS. 10A-10B show the calibration of the indophenol blue method for estimating NH ₄ ⁺ /NH ₃ concentration, using NH ₄ Cl solutions of known concentration as standards. FIG. 10A are UV-Vis curves of indophenol assays with NH ₃ . FIG. 10B shows calibration assays with absorbances at 679 nm used for calculation of NH ₃ concentrations, and the fitting curve shows good linear relation of absorbance with NH ₃ concentration. [0085] FIGS.11A-11D show electrocatalytic performance of N ₂ reduction to NH ₄ ⁺ /NH ₃ over the Mo/HNG catalyst. FIG.11A shows potential-dependent FEs and partial current densities of NH ₄ ⁺ /NH ₃ for NRR on Mo/HNG, Mo/NG, 2Mo/HNG catalysts determined from chronoamperometric measurements. FIG. 11B shows durability and corresponding FE of Mo/HNG with testing periods of 20000s. FIG. 11C shows chronoamperometric curves of measurements with Mo/HNG at various electrode potentials ranging from -0.00 V to -0.20 V vs RHE in the N ₂ -saturated 0.05 M H ₂ SO ₄ solution. FIG. 11D shows ¹ H NMR spectra of ¹⁴ NH ₄ Cl and ¹⁵ NH ₄ Cl standard, and the resultant electrolyte obtained from the chronoamperometric NRR measurement of Mo/HNG at -0.05 V using ¹⁴ N ₂ and ¹⁵ N ₂ as the isotopic nitrogen source. [0086] FIGS. 12A-12C show computational studies of electrochemical N ₂ reduction. FIG. 12A shows optimized structure models of MoN4, MoN3, MoN3 with two adjacent vacancies (MoN ₃ +2Vc), and corresponding Bader charge density upon adsorption of N ₂ , where isosurfaces indicate charge accumulation and depletion, respectively. FIG. 12B shows free energy diagram for the NRR on the MoN4, MoN3, MoN3+2Vc catalytic centers at U = 0 V (with the energy barrier of corresponding potential-determining step in electrochemical NRR with distal pathways). FIG.12C shows optimized configurations of reaction intermediates in NRR on MoN ₃ +2V _c center. [0087] FIGS. 13A-13B show the free energy diagram for the NRR on the MoN ₄ catalytic centers with distal pathway and alternating pathway, respectively, at U = 0 V. [0088] FIGS.13C-13D illustrate reaction intermediates are for distal pathway and alternating pathway of FIGS.13A-13B, respectively. [0089] FIGS. 14A-14B show the effects when using a pressure cell. FIG. 14A shows the nitrogen reduction reaction (NRR) current increase with increased pressure while FIG. 14B shows the change in the FE upon pressure change. [0090] FIG.15 is a schematic illustration of the pressure cell utilized for the effects shown in FIGS.14A-14B. DETAILED DESCRIPTION [0091] The present invention relates methods for the production of ammonia from dinitrogen (N ₂ , and often referred to as “nitrogen”) using electrochemical devices having atomic metal on graphene for electrochemistry. Synthesis and Fabrication Methods [0092] An atomic Mo catalytic site anchored on a holey nitrogen-doped graphene framework (Mo/HNG) has been developed, which achieved an efficient activity toward N ₂ electrochemical reduction to NH ₃ with excellent selectivity under ambient conditions. [0093] As illustrated in FIG. 1A, the synthetic strategy for the atomic Mo catalytic sites anchoring on a holey nitrogen-doped graphene catalyst includes two steps: (1) the synthesis of HNG through simultaneous nitrogen doping and potassium salt assisted activation of GO, and (2) the subsequent introduction of Mo on HNG with nitrogen coordination. [0094] Holey nitrogen-doped graphene (HNG) with a continuous porous skeleton and abundant edges containing nitrogen-coordination sites was prepared through a convenient potassium salt assisted activation method; the HNG was then used as substrates for the subsequent Mo loading. [Ludwinowicz 2015; Jalilov 2015]. Mo/HNG exhibited an excellent Faradaic efficiency (FE) of 50-68% for NH ₃ production, the highest efficiency that has been to date, at 0.1 V vs reversible hydrogen electrode (RHE) in 0.1 M HCl, the overpotential of which is the smallest within all the nitrogen reduction catalysts. Moreover, Mo/HNG catalysts also had high catalytic stability toward N ₂ electrochemical reduction at different applied potentials, suggesting Mo/HNG as a durable NRR electrocatalyst for applications and a possible alternative for the thermal Haber-Bosch process. See also Zhang C., “Atomic Metal On Graphene For Electrochemistry,” dated January 2019, (“Zhang 2019,” incorporated herein by reference), showing atomic Mo catalytic sites anchored on a holey nitrogen-doped graphene framework (Mo/HNG), which achieved an efficient activity toward N ₂ electrochemical reduction to NH ₃ . The Zhang 2019 thesis work could not efficiency suppress the HER current because he vacuum-treated the catalysts at 100°C. The vacuum-treatment and elevated temperature yielded an inferior catalyst. All this resulted in Zhang 2019 FE of ~14% with an overpotential of 0.47 V, affording a production rate of 6 μA mg ^-1 catalyst at -0.2 V vs. RHE (reference reversible hydrogen electrode). [0095] It has been discovered and disclosed here that when the process for preparing the electrode is performed at room temperature and pressure, rather than 100°C under vacuum as in Zhang 2019, remarkably and unexpectedly, this had a dramatic increase in the FE from 14% to 68%. This was because a higher temperature electrode preparation of Zhang 2019 caused the oxidation of Mo(V) to Mo(VI), and Zhang 2019’s lower pressure changed the surface condition during the drying process, causing the graphene to aggregate and to expose fewer active sites on the catalyst, which had resulted in the Zhang 2019 Faradaic efficiency of 14%. In 2019, a FE of 14% was on the high end of FEs in the literature. Encouragingly, in addition to increasing the FE from 14% to 68% through our new catalyst preparation method, the overpotential decreased from the former 0.47 V to 0.37 V, and the production rate increased from the former 6 μA mg ^-1 catalyst at -0.2 V vs. RHE to 7.84 μA mg ^-1 catalyst at -0.10 V vs. RHE. See FIG.1B. [0096] The atomic molybdenum anchoring on holey nitrogen doped graphene materials are produced using an inexpensive and commercially scalable approach. The materials are highly conductive, nanoporous, and stable. Holey nitrogen-doped graphene (HNG) with a continuous porous skeleton and abundant edges containing nitrogen-coordination sites can be prepared through a convenient potassium salt assisted activation method; the HNG was then used as substrates for the subsequent Mo loading. A new type of nitrogen-coordinated molybdenum electrocatalytic site for nitrogen fixation under room temperature has been developed. An efficient activity toward N ₂ electrochemical reduction to NH ₃ with excellent selectivity under ambient conditions is achieved. Mo/HNG exhibited an excellent Faradaic efficiency (FE) of 68% for NH ₃ production, the highest efficiency reported to date, at -0.10 V vs the reference reversible hydrogen electrode (RHE) in 0.1 M HCl, the overpotential of which is the smallest within all the nitrogen reduction catalysts. Moreover, Mo/HNG catalysts also had high catalytic stability toward N ₂ electrochemical reduction at different applied potentials, revealing Mo/HNG as a durable NRR electrocatalyst for applications and a possible alternative for the thermal Haber-Bosch process. [0097] The synthesis of atomic molybdenum anchoring on holey nitrogen-doped graphene (Mo/HNG) material and fabrication of Mo/NHG based electrochemical devices can be performed utilizing the following steps: (a) Production of holey nitrogen-doped graphene from graphene oxide; (b) Homogenous dispersion of molybdenum atoms anchoring on holey nitrogen- doped graphene; (c) fabrication of electrochemical device. [0098] Production of holey nitrogen-doped graphene through a simultaneous nitrogen doping and potassium salt assisted activation method of graphene oxide (GO). During this step, for example, typically 1 mL 0.1 mol/L solution of potassium chloride (or potassium acetate) was added into 25 mL of 2 mg/mL dispersed GO solution followed by 3 h bath sonication. Lyophilization of the solution was performed to obtain a GO foam with evenly distributed KCl. After that, the GO/KCl foam was annealed under an Ar (100 sccm) and NH ₃ (50 sccm) atmosphere at 750 °C for 1 h to obtain holey nitrogen-doped graphene (HNG). The reduction and nitrogen doping were achieved simultaneously for GO. Moreover, a potassium salt induced activation and etching process occurred on graphene with high temperature treatment, resulting in the appearance of copious pores on the surface of HNG, as observed in the transmission electron microscopy (TEM) images [0099] For example, in the first step, a solution of potassium chloride (KCl) was added into the dispersed GO solution followed by bath sonication. Lyophilization afforded a GO foam with evenly distributed KCl. The GO/KCl foam was annealed under Ar/NH ₃ atmosphere at 750 °C for 1 h to obtain HNG-750. The reduction and nitrogen doping were achieved simultaneously, which is consistent with prior approaches. [Zhang 2017; Fei 2015]. A potassium salt-induced activation and etching process also occurred on the graphene during the high-temperature treatment, resulting in the appearance of copious pores on the surface of HNG-750 (the number represents the treatment temperature in °C), as shown in the comparative transmission electron microscopy (TEM) images before and after hole formation. See FIGS.2A-2B. [0100] Based on the high-resolution TEM images, the intermittent micropores were uniformly distributed on nitrogen-doped graphene with diameters ranging from 4 nm to 8 nm. The nitrogen-doped graphene prepared at the same annealing temperature except without KCl treatment is devoid of holes as shown in FIGS.2A-2C. The surface morphology of HNG-750 was further probed with scanning electron microscopy (SEM) in FIGS. 3A-3B, exhibiting a typical stacked graphene sheet network. [0101] For the second step of Mo introduction, an acetonitrile (CH ₃ CN) solution of molybdenum(V) chloride (MoCl ₅ ) was mixed with the HNG-750 followed by bath sonication. The Mo content was controlled at 0.96 at%, based on the weight of HNG-750, to avoid potential aggregation of the Mo atoms. With abundant nitrogen coordination sites on the holey nitrogen- doped graphene including pyridinic and pyrrolic nitrogen, HNG-750 could functionalize as a hosting ligand to react with MoCl _5, thereby anchoring the Mo species. After reaction between HNG-750 and MoCl5, Mo/HNG was obtained through filtration and washing with ethanol. The high-resolution TEM image of Mo/HNG shows the preservation of structural holes and the absence of any Mo-based nanoparticle phases on the graphene surface (FIG. 2C). The successful incorporation of atomically dispersed Mo sites is further confirmed through the atomic-resolution high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) measurement (see FIG. 2D, magnified portion highlighted with circles), verifying no agglomeration of metallic species such as nanoparticles or clusters. The homogenous distribution of the C, N, and Mo elements throughout the graphene framework was further confirmed by the energy-dispersive X-ray spectroscopy (EDS) mapping spectrum. FIG.2E. The Mo mass loading was determined to be up to 2.4 wt% according to inductively coupled plasma optical emission spectroscopy (ICP-OES). [0102] Based on high resolution TEM (HRTEM) images (FIGS. 2A-2C) and pore size distribution curves (FIGS. 8C-8D), the micropores are uniformly distributed on nitrogen- doped graphene with diameters ranging from 2 nm to 10 nm. See also TABLE I. TABLE I BET surface analysis of HNG and Mo/HNG made with different potassium sources sample BET surface area (m ² g ^-1 ) Pore width (nm) HNG-KOAc 478 2.8 HNG-1/5KOAc 562 2.8 HNG-KCl 237 4.2 Mo/HNG-KOAc 266 2.8 Mo/HNG-1/5KOAc 203 3.2 Mo/HNG-KCl 74 3.2 [0103] Introduction and dispersion of molybdenum atoms anchoring on holey nitrogen-doped graphene. For the step of Mo introduction, for example, molybdenum(V) chloride (MoCl ₅ ) was dispersed in acetonitrile (CH ₃ CN) to form a 1 mg/mL solution, 4 mL of which was mixed with the as-prepared HNG material followed by 6 h bath sonication. The Mo content was controlled at 0.96 at% based on the weight of HNG to avoid potential aggregation of the single metals atoms into nanoparticles. With abundant nitrogen coordination sites on HNG, including pyridinic and pyrrolic nitrogen, HNG-750 (meaning prepared at 750°C) functioned as a supporting ligand to react with MoCl ₅ and anchor the Mo species. Mo/HNG-750 was then obtained following filtration through a PTFE filter (Sartorius, 11806), 3 times ethanol washing and elevated temperature annealing (650 °C for 0.5 h). Mo/HNG shows the absence of any Mo-based nanoparticles on the graphene surface and only individual Mo atoms. The homogenous distribution of the C, N, and Mo elements throughout the graphene framework was further confirmed by energy-dispersive X-ray spectroscopy (EDS) mapping spectrum (FIG.2E). The Mo mass loading was determined to be up to 4.5 wt% according to inductively coupled plasma atomic emission spectrometry (ICP-AES). [0104] Electrochemical device fabrication based on Mo/HNG. For this step, for example, a catalyst ink was prepared by dispersing Mo/HNG material and 5 wt% Nafion solution in into 4:1 (v/v) water/ethanol with 3 h sonication. The catalyst ink was then loaded onto carbon fiber paper at atmosphere and left dry in air as electrode. It was discovered that a higher temperature would cause the oxidation of Mo(V) to Mo(VI), and a lower pressure would change the surface condition during the drying process, causing the graphene to aggregate and to expose fewer active sites. Thus, the Faradaic efficiency was significantly and unexpectedly increased by the process of using room temperature and atmospheric pressure for the catalyst formation. This resulted in a significant and dramatic increase in the FE. An H-cell configuration was used for electrochemical nitrogen fixation with an N ₂ saturated electrolyte. A gas diffusion cell was also attached to increase the production rate. [0105] Alternatively and additionally, the processes can included the following. [0106] The atomic dispersed metal can be different transition metals. [0107] The substrate can be other nitrogen-doped carbons, carbon nanotubes or graphene materials. [0108] The percentage of transition metal atoms in the materials can be different. [0109] The preparation conditions of holey nitrogen-doped graphene can be different. [0110] Certain binding polymer or nanomaterials can be added or mixed with the holey nitrogen-doped graphene materials to enhance the electrochemical performance of the electrode. [0111] Addition of a gas diffusion cell to increase the production rate. Properties [0112] To investigate the structures and compositions of HNG-750 and Mo/HNG, a series of characterizations were performed, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman measurements. In high-resolution N 1s XPS spectra of HNG- 750 (FIG.4A), four deconvoluting peaks at 398.4 eV, 399.9 eV, 401.0 eV and 403.1 eV were designated to pyridinic-N (55 at%), pyrrolic-N (16 at%), graphitic-N (20 at%), and N-oxides (8.9 at%), respectively. In comparison with the KCl-treatment-free NG-750, the ratio and intensity of the pyridinic-N peak are significantly enhanced in HNG-750. The pyridinic N atoms have been shown to be preferentially located at the edges of graphene. [Guo 2016; Liu 2016]. During the thermal annealing and nitrogen-doping process, more nitrogen species are likely introduced or migrated to the exposed in-plane edges of these pores of holey nitrogen- doped graphene, leading to this elevated ratio of pyridinic-N. Raman spectra given in FIG.4B show that the intensity of D band (~1350 cm ^-1 ) to G band (~1580 cm ^-1 ) ratio (ID/IG) of HNG- 750 was 1.11, slightly larger than that of NG-750 (I _D /I _G = 0.95), presumably owing to more defects and holey structure existed on graphene layers. [Eckmann 2012]. [0113] FIG.5A shows the XRD spectra of Mo/HNG and HNG-750. Both Mo/HNG and HNG- 750 exhibited a broad peak at ~24°, which were attributed to the (002) facets of graphene. No characteristic peak of Mo-based nanocrystalline was observed in the XRD pattern of Mo/HNG, which is in accordance with the results of TEM and HAADF-STEM images. The Brunauer– Emmet–Teller surface areas of Mo/HNG were measured as 189 m ² g ⁻¹ . See FIGS. 5B-5C. TABLE II shows the Brunauer–Emmet–Teller surface areas and average pore sizes of HNG- 750, Mo/HNG, NG-750, and Mo/NG. [0114] FIG.4G displays the Fourier transform (FT) k ³ -weighted χ(k) function of the extended X-ray absorption fine structure (EXAFS) spectra of Mo/HNG. The peaks at 1.17 Å in Mo/HNG and 2.47 Å in Mo foil can be assigned to the Mo-N(O) and Mo-Mo path, respectively, further indicating no Mo-Mo coordination exists in Mo/HNG. The Mo K-edge X-ray absorption near- edge structure (XANES) of Mo/HNG compared with standard Mo foil is shown in FIG.4H. The positively shifted near-edge of Mo/HNG in comparison to Mo-foil suggests that the higher valence state of Mo. FIG. 4I highlights the pre-edge features at approximately 20,003 eV, which signals 4d and 5p orbital hybridization of the Mo central atoms. [0115] The high-resolution XPS Mo 3d signal of Mo/HNG shows two well-separated spin- orbit component sharp peaks at 232.4 eV and 235.6 eV, assigned to Mo 3d _5/2 and Mo 3d _3/2 , respectively, indicating a potential uniform valence state of Mo species in Mo/NG close to Mo(V) or Mo(VI). See FIG.4E. [0116] In the high-resolution N 1s XPS spectrum of Mo/HNG, there is a shoulder peak appears at 399.7 eV when compared to that of HNG-750, possibly caused by pyridinic-N species bonded to Mo sites (Mo-N _x ), as shown in FIG. 4F along with the estimated deconvolution. This distinctive difference also strongly supports the existence of coordination between Mo and nitrogen in the Mo/HNG catalyst. [0117] Atomic molybdenum anchoring on holey nitrogen-doped graphene materials features the following properties: [0118] Easy synthesis with a scalable approach. The production of these materials is performed with scalable manufacturing procedures with normal conditions. Raw materials are commercially available and inexpensive chemicals (graphene oxide from the improved Hummer’s method as disclosed by Tour, and commercially available NH ₃ for catalysts preparation, KCl (or KOAc), MoCl ₅ and CH ₃ CN). See FIG.1A. [0119] Nanoporous structure of holey nitrogen-doped graphene. The holey nitrogen-doped graphene materials have highly nanoporous and wrinkled structure as shown in SEM and TEM images. [0120] Atomic dispersion of Mo in the material. With abundant nitrogen coordination sites on holey nitrogen-doped graphene, including pyridinic and pyrrolic nitrogen, holey nitrogen- doped graphene functioned as a supporting ligand to anchor the Mo species (FIGS.4A-4B). The TEM image and XRD characterization (FIGS. 2C and 4D) of Mo/HNG-750 shows the absence of any Mo-based nanoparticles on the graphene surface. A homogenous distribution of Mo species throughout the graphene framework was observed by EDS mapping (FIG.2E). The isolated Mo atoms on holey nitrogen-doped graphene substrate were further confirmed by HAADF-STEM characterizations (FIG.2D). [0121] High efficiency of atom utilization. In contrast to metal nanoparticle based electrocatalyst, the atomic dispersion of metal in the material directly exposes the optimal number of active sites to the electrolyte. Therefore, it maximized the transition metal atom utilization efficiency for a range of reactions including electrochemical nitrogen fixation, which also significantly reduces the precious metal consumption and cost in the preparation of catalysts for ammonia formation. [0122] Excellent electrochemical performance and durability of nitrogen fixation on Mo/NHG material with high Faradic efficiency of ammonia production. Mo/HNG exhibited an excellent Faradaic efficiency (FE) of 68% for NH ₃ production, the highest efficiency that has been reported to date, at -0.10 V vs reversible hydrogen electrode (RHE) in 0.1 M HCl, the overpotential of which is the smallest within all the nitrogen reduction catalysts. The hydrazine concentration was below the detection limits for the results of Mo/HNG, demonstrating its high electrochemical selectivity towards NH ₃ . Moreover, the Mo/HNG catalysts also had high catalytic stability toward N ₂ electrochemical reduction at different applied potentials with no obvious current loss after hours of constant electrolysis. The type and the amount of potassium precursors could also be used to adjust the surface area, pore widths, coordination environments of Mo atoms and NRR performance. See FIGS.6A-6D, 7, 8A-8D, 12A-12B, and 13A. Electrochemical Reduction Of N ₂ to NH ₃ On The Mo/HNG Catalysts [0123] Electrochemical measurements were conducted to evaluate the electrocatalytic activity of the Mo/HNG towards N ₂ reduction. The electrocatalysts were deposited on a carbon fiber paper (CFP) electrode as a working electrode with the use of Ag/AgCl as the reference electrode and 0.05 M H ₂ SO ₄ as an electrolyte. The counter electrode of the Pt mesh was separated from the working and reference electrode by a Nafion 117 membrane to provide sufficient ion exchange between the two chambers, as well as to avoid the permeation of reaction products. N ₂ gas is purged into the chamber of the working cathode electrode, where N ₂ and H ⁺ combine with transported electrons from the electrode to generate the N ₂ reduction product. Based on the Nernst equation, the standard potential for the reduction of N ₂ to NH ₃ was 0.27 V vs RHE (Ag/AgCl KCl saturated reference electrode has been calibrated on reversible hydrogen electrode). [0124] A comparison study of the linear sweep voltammetry (LSV) curves of Mo/HNG under Ar and N ₂ -saturated 0.05 M H ₂ SO ₄ electrolyte was performed (see FIGS. 9A-9B). For Mo/HNG, the current density in N ₂ -saturated electrolyte was slightly higher than that in Ar- saturated electrolyte at the potential ranging from 0.00 to -0.20 V vs RHE, indicating a possible interaction between Mo/HNG catalyst with N ₂ during the electrochemical sweeping. With the applied potential below -0.20 V vs RHE, the current density of Mo/HNG in N ₂ -saturated electrolyte resembles that in Ar-saturated electrolyte, suggesting that the HER is the predominant reaction in this circumstance. [0125] The NRR catalytic performance of Mo/HNG was further tested through chronoamperometric measurements at various electrode potentials ranging from 0.00 V to -0.20 V in N ₂ -saturated 0.05 M H ₂ SO ₄ electrolyte. After each 2000 s test for Mo/HNG at a selected constant potential, the electrolyte in the chamber of the working electrode was collected. In order to quantify the concentration of NH ₄ ⁺ /NH ₃ product in the electrolyte, a colorimetric indophenols blue method was employed with a calibrated standard curve (FIGS. 10A-10B, with curves 1001-1006 for concentrations of 0, 0.25, 0.5, 1.0, 2.0 and 4.0 μg/mL, respectively). [Bolleter 1961]. [0126] The potential production of hydrazine was also examined with a p-(dimethylamino)- benzaldehyde-based method. [Watt 1952]. As controls, atomic Mo was synthesized on nitrogen-doped graphene (Mo/NG) catalyst through NH ₃ annealing of a GO/MoCl ₃ precursor with previously reported methods [Zhang 2018; Fei 2015], and Mo/HNG with doubled Mo loading (2Mo/HNG), that were tested with the same electrochemical conditions. [0127] The corresponding FEs of Mo/HNG, 2Mo/HNG and Mo/NG with various electrode potentials are plotted in FIG.11A. FIG.11A also shows the calculated corresponding partial current densities of Mo/HNG, 2Mo/HNG and Mo-HNG for NH ₄ ⁺ /NH ₃ production. Interestingly, at all applied potentials, Mo/HNG exhibited much higher FEs and partial current densities for NH ₃ production than that of 2Mo/HNG and Mo/NG. This phenomenon reveals that the holey nitrogen-doped graphene structure and controlled Mo loading are an important part for the formation of single atomic Mo-based active sites towards NRR in comparison with non-holey nitrogen-doped graphene. The FE of NH ₄ ⁺ /NH ₃ production for Mo/HNG reached the maximum value of 50.2% at -0.05 V vs RHE, where it is 34.2% for Mo/NG and 8.1% for 2Mo/HNG. The Mo/HNG electrocatalyst in the N ₂ saturated electrolyte exhibits approximately 2.3 times higher NH ₄ ⁺ /NH ₃ production yields than that of Mo/NG. For both Mo/HNG and Mo/NG, the partial current densities of NH ₄ ⁺ /NH ₃ production drastically increased when the applied potential shifted from 0.00 V to -0.05 V vs RHE, showing the range of onset potential for electrochemical NRR occurrence. After -0.05 V vs RHE, the partial current densities gradually drop since the competitive HER becomes the predominant reaction on the electrodes. [0128] To further substantiate that the detected NH ₄ ⁺ /NH ₃ derived from the electrochemical activation of N ₂ and not from the nitrogen atoms on the HNG substrate, complementary isotope labeling experiments were performed using ¹⁵ N ₂ (99 atom% ¹⁵ N) and abundant natural ¹⁴ N ₂ (99.6 atom% ¹⁴ N) as nitrogen sources, respectively. [Anderson 2019]. As illustrated in FIG. 11D, the NH ₄ ⁺ splitting patterns in ¹ H nuclear magnetic resonance ( ¹ H NMR) spectra of the resultant electrolytes demonstrate strong consistency with the corresponding isotopic ¹⁵ N ₂ or ¹⁴ N ₂ source supplied during electrolysis at -0.05 V vs RHE. Meanwhile, no NH ₃ was detected in the control experiments using Ar as the gas supply at the same testing potential (FIG.11D), further substantiating the reliability of the results. Moreover, the hydrazine yields were both below the detection limit for the results of Mo/HNG and Mo-NG, demonstrating their high electrochemical selectivity towards NH ₃ formation. [0129] Furthermore, to gain better insight into the intrinsic origin of improved NRR performance from such edge anchored single-atom Mo sites, computational studies under the scheme of spin-polarized density functional theory were performed, focusing on the adsorption behaviors and possible reaction pathways on the Mo catalytic centers. [0130] As illustrated in FIG. 12A, three representative types of hosting environment models of nitrogen-doped graphene have been constructed and investigated as active sites: Mo atoms embedded upon a graphene lattice with typical four nitrogen coordination (MoN ₄ ), edge- anchored Mo with three pyridinic nitrogen as binding sites (MoN ₃ ), MoN ₃ site with two neighboring vacancies of graphene matrix (MoN3+2Vc), respectively. It was found that the distal pathway is more feasible than the alternating pathway (FIGS.13A-13B) on MoN ₄ sites, in accordance with the observed absence of hydrazine during NRR in Mo/HNG. In FIGS. 13A-13B, curves 1301a-1301b are for 0 V, and curves 1302a-1302b are for -1.07 V. [0131] The free energy diagram of intermediates in the distal pathway without external potential is shown in FIG. 12B. FIG. 12B shows curves 1201-1203 for MoN4, MoN3, and MoN ₃ + 2Vc, respectively; the energy barrier of corresponding potential-determining step in electrochemical NRR with distal pathways are shown at arrows 1204-1206. [0132] All three single Mo configurations exhibit an exothermic nitrogen adsorption (formation of *N ₂ ) process, indicating a preferential activation of dinitrogen. Based on the MoN4 center, the potential-determining reaction bottleneck is identified as the final hydrogenation step of *NH ₂ intermediate (*NH ₂ + NH ₃ + H ⁺ + e- → *NH ₃ +NH ₃ ) and the reaction barrier is calculated to be 0.68 V (arrow 1204). In contrast, the potential-determining step of MoN ₃ and MoN ₃ +2V _c was shifted to the first hydrogenation step of bonded dinitrogen (*N ₂ + H ⁺ + e- → *NH ₃ ), meanwhile featuring reduced reaction barriers of 0.56 V (arrow 1205) and 0.39 V (arrow 1206), respectively, which is much lower than that of Mo-N ₄ and reported noble metal catalysts. [Skúlason 2012]. The presence of vacancies induced by the holey structures on graphene drastically lower the formation energy of *NNH intermediates. The experimentally observed low overpotential of NRR towards NH ₃ could be attributed to this free energy favorable distal pathway on MoN ₃ -2V _c sites, thereby leading to the more intriguing NRR activity of Mo/HNG compared to that of Mo/NG. Uses [0133] The present invention includes the preparation of highly efficient Mo-based NRR electrocatalyst in acidic electrolytes under ambient conditions, which includes stabilized single Mo atoms anchored on holey nitrogen-doped graphene synthesized through a convenient potassium salt assisted activation method. HNG of the present invention are efficient substrates for dispersing and bonding atomic Mo species as Mo-N _x moieties, which are considered the active sites for NRR. The incorporation of Mo into edge-rich holey nitrogen-doped graphene scaffold along with the substrate vacancies synergistically promotes electrochemical NRR with low overpotential. [0134] At -0.05 V vs a reversible hydrogen electrode (RHE), an electrode having the resultant electrocatalyst immobilized on carbon fiber paper can attain an exceptional Faradaic efficiency (more than 50%) and a NH ₃ yield rate of 2.7 μg h ^-1 mgcat ^-1 with low overpotentials. Compared to the original graphene without holes, the edge coordinated Mo atoms and the existence of vacancies on holey graphene lower the overpotential of N ₂ reduction, thereby promoting the NRR catalytic activity. [0135] Embodiments of the present invention provide for single-atom catalysis that would be beneficial to ambient N ₂ fixation, and replacement of classical synthesis processes that are very energy-intensive. [0136] The Mo/HNG materials can be used as electrocatalysts for room temperature electrochemical ammonia synthesis in forms of large-scale electrolysis devices and microscale devices. Compared to the traditional Haber-Bosch process, electrochemically reduction of nitrogen with Mo/HNG materials can significantly enhance the energy efficiency and lower the cost for purification, transportation and storage, as an alternative solution in industrial application and production. This can lead to distributed ammonia production using small production facilities. This becomes particularly important for local fuel generation as ammonia is being used as an alternative fuel for shipping and aircraft wherein combustion affords only N ₂ and water as evolution products; no CO ₂ emissions. This is referred to as “green ammonia”. [Scott 2020]. Moreover, ammonia is viable and attractive as a hydrogen source in fuel cells. [Lan 2014]. [0137] For the electrochemical reduction of N ₂ with the counter reaction being the oxygen evolution reaction (OER) (schematics shown in FIGS.6A and 7), calculations were performed with the present low-end industrial electricity price (2 cents per kWh) and 100% Faradaic efficiency, the estimated direct electrochemical nitrogen reduction cost with ammonia, and oxygen generation will be 1.172 eV*96485 C/mol*3/(3.6*10 ⁶ J/kWh)/17 g/mol *10 ⁶ g/metric ton*0.02 $/kWh (industrial electricity rate) = $110/metric ton. This is at 100% FE and the FE of the present invention, at 68%, is close to that value. This could also provide an enormous reduction in the CO ₂ greenhouse gas generation over the Haber-Bosch process while permitting local generation without the need for enormous Haber-Bosch plants. [0138] If other reactions, such as the oxidation of natural gas, is used in electrochemical nitrogen reduction as the counter reaction instead of the oxygen evolution reaction (OER), part of the energy will come from the oxidation of natural gas, and thus the estimated price will be much lower than $110/metric ton of ammonia at 100% Faradaic efficiency. However, carbon- containing chemicals, e.g., CH ₃ OH and CO ₂ would be evolved in the overall process. [0139] Portable devices to synthesize NH ₃ may be advantageous to use. Most parts of the devices are now widely used in commercial fuel cells, so they are readily available to obtain and assemble into the devices to be used in industry. In this manner, ammonia, instead of hydrogen, could be synthesized easily in places with abundant renewable energy. The cost can also be reduced as a result of the low-cost electricity. [0140] In embodiments that resulted in partial current density (of 25.8 μA cm ^-2 with a rate of 5.4 μg/h cm ^-2 and 89 pmole/s cm ^-2 ), a 16% Faradaic efficiency was achieved, which meant a cost of $688/metric ton for ammonia. Even by increasing these to 20% Faradaic efficiency, this cost would be $550/metric ton for ammonia. [0141] As shown in FIGS.6B-6C, Faradic efficiency result of ~68% has been obtained with Mo-HNG-750 at -0.10 V vs RHE (with low current density and rate) (current density achieved ~7.8 μA cm ^-2 with a rate is 1.6 μg/h cm ^-2 and 27 pmole/s cm ^-2 ). By achieving 68% Faradaic efficiency, which is among the highest Faradaic efficiency reported to date, the price is lowered to $164/metric ton if the oxygen evolution reaction (OER) is used as the counter reaction. If natural gas oxidation reaction is involved, the price would be even lower. [0142] This compares with the average cost of ammonia of ~$600/metric ton over the past 10 years (H2 feedstock coming from natural gas so massive CO ₂ generation in the process). But this is also largely related with the electricity price and origin of the H ₂ feedstock. If the H ₂ feedstock in the HB process is from electrolysis, the price of ammonia will be higher than $600/metric ton by the HB process. [0143] These results are limited by the low N ₂ concentration in the solution. The current density and production rate can increase with the use of gas diffusion electrodes, which can increase the N ₂ concentration on the electrode, as shown in FIGS.14A-14B. [0144] FIGS.14A-14B show the effects for when using a pressure cell. FIG.14A shows the NRR current increase with increased pressure while FIG. 14B shows the change in the FE upon pressure change. 0 kPa means normal atmospheric N ₂ . 30 kPa and 100 kPa were the added pressures above the normal atmospheric N ₂ . Increasing the pressure alone turns out not to adequately increase the production rate since the FE falls in the process as seen in FIG.14B. Hence, the process provides for moving toward increasing the number of SAC sites while mitigating those atom agglomerations by using smaller carbon particles such as on graphene quantum dots as the substrates. [0145] FIG. 15 is a schematic illustration of the pressurizable electrochemistry cell 1500 utilized for the effects shown in FIGS.14A-14B. Pressurizable electrochemistry cell 1500 can be a four-section plastic eletroysis cell, which includes anode 1501 (such as a Pt-Cu anode, cathode 1502 (such as Cu foil to carbon paper cathode), rubber membranes 1503, film 1504 (Nafion), and carbon paper with catalysis 1505. Electroyte can be introduced through ports 1506 (such as by using a syringe) with shutoff valves 1507. Pressurized nitrogen can be introduced through ports 1508. Pressurizable electrochemistry cell 1500 further has plates 1509 (plastic or steel plates), brass pressure rings 1510, screws 1511, and spring washers 1512. Pressurizable electrochemistry cell 1500 further has a reference electrode 1513. Arrow 1514 show concentrated pressure on rubber membranes 1503. [0146] The design of making the pressurizable cell for electrochemistry is based on separating the wetted components, which are generally made from plastic, from the structural components, which are generally mostly steel. The fundamental problem of using metal parts both for wetted endplates for the cell, as well as providing rigidity to withstand high pressures, is that stainless steels in general gain their protection from a robust oxide layer. However, the reducing environment of the cathode could strip off the oxide layer exposing the bare metal, and in this case, the presence of a halogen acid like HCl is a corrosive double problem against the metal. Hence, exotic alloys or precious metal electroplated coatings would be needed to prevent corrosion, greatly increasing the cost of the cell. [0147] However, by using a steel cage design, this mitigates this dilemma. With no need for structural rigidity, the electrochemistry cell can be made by 3D printing of plastic or by more traditional fabrication processes. Since the external cage is not in contact with the acidic electrolyte, it can be low-cost galvanized steel plates with black steel oxide high-strength screws. Using off-the-shelf steel components, the machining can be just drilling four to eight holes in each of two plates. Although the brass ring was machined to provide a self-centering lip, because it is used in compression, this can also be a printed plastic part. [0148] For example, as can be used in pressurizable electrochemistry cell shown in FIG.15, the electrochemistry cell includes four plastic plates (such as 6 cm square) and secured with screws (such as four M5 screws at the corners). Two of the plastic plates are end caps with gas feed connections, and two other of the plastic plates are in the middle with each have about a volume (such as a volume of 1 cm ³ ) for the liquid electrolyte. Chromatography-style fittings (such as connecting to 1/8 inch PTFE tubing and syringes) are used to fill these two internal volumes. [0149] There are three rubber membranes between the plates intended to provide a seal. In addition, there is an O-ring (about 2 cm diameter) embedded in each of the two end plates. However, the porous carbon paper extends beyond the O-ring, so that the rubber membrane, rather than the O-ring is the main seal. Nafion film separates the two liquid cells, and is held in place by the middle rubber membrane, which provides both a seal between the two cells and prevents leakage to the outside. [0150] Pressurizing the nitrogen can be beneficial for a more rapid conversion, by increasing the concentration of the N ₂ . However, utilizing high-pressure nitrogen can result in fluid leaks from the one or both cells, such as when the pressure was greater than 0.3 bar above atmospheric pressure. For instance, the four screws on the corners of cell place the greatest compression of the rubber membrane at the corners. This in turn can cause the plastic plates 1509 to flex and bow outward, decreasing the pressure on the rubber membrane in the middle between the corner screws. Hence pressurizing the can then can cause the fluid to seep out. [0151] A pressurized plate and ring method was used in the cell of FIG.15 so that the cell can be pressurized. A brass ring is placed on each end of the complete cell (which was approximately 1.2 inch (3 cm) ID and 2 inch (5 cm) OD). When these two rings were pressed inward against the end plates, this placed the highest pressure on the three rubber membranes in the corresponding same area, approximately forming an annulus of highest pressure (about 1 cm) just outside the internal volume that contains the electrolyte. This created an annular sealing ring in each membrane. In addition, because the pressure was applied to the plastic end plates by a ring, the pressure is uniform around the circumference, in contrast to just the four bolts on the corners, which had previously created localized regions of high pressure at the corners where it provides little sealing function, and much less pressure in middle where fluid can be forced out. [0152] The brass rings (which in FIG. 15 had lips to keep them centered), are held in an external frame of two steel plates, such as 3 inch square and ¼ inch thick, and with a 1.3 inch hole, which provided space for the nitrogen gas connections in the middle of the two plastic end plates. Chromatography-type fittings were utilized. [0153] This formed a symmetric compression cage. For instance, one of the steel plates had eight holes and the mating plate had eight tapped holes to accept eight screws (such as 10-32 high strength alloy steel screws) which straddle the outside of the assembled plastic cell, forming a cage-like structure. A compressible spring washer was under each screw head. This arrangement allowed for uniform pressure to be applied to the brass rings on each end of the cell and thereby provided compression of the plastic plates and rubber membranes in the annulus around the liquid filled cavities in the two center plastic plates. The screws were lightly lubricated with silver-bearing grease to prevent galling and possible seizure from repeated use. [0154] The compression cage did not change the electrolysis cell. The compression cage was entirely external and did not require any modification of the electrolysis cell. [0155] Valves are also used to prevent fluid loss. Because the two internal cells were filled (such as by using syringes), valves were added to keep the pressurized nitrogen from expelling the liquid back. In addition, nitrogen pressure was applied equally to both ends to avoid creating a differential pressure across the Nafion membrane or across the catalyst film deposited on the carbon paper. [0156] The pressurizable cell also has a sealed reference electrode. The reference glass electrode in the electrolyte between the Nafion and the carbon paper with catalyst was needed to be sealed to prevent liquid loss, and with little or no air at the top because this can compress, which in turn would allow a nitrogen bubble to enter the liquid electrolyte in the internal cells. [0157] While embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. The embodiments described and the examples provided herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention. The scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. [0158] The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated herein by reference in their entirety, to the extent that they provide exemplary, procedural, or other details supplementary to those set forth herein. [0159] Amounts and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a numerical range of approximately 1 to approximately 4.5 should be interpreted to include not only the explicitly recited limits of 1 to approximately 4.5, but also to include individual numerals such as 2, 3, 4, and sub-ranges such as 1 to 3, 2 to 4, etc. The same principle applies to ranges reciting only one numerical value, such as “less than approximately 4.5,” which should be interpreted to include all of the above-recited values and ranges. Further, such an interpretation should apply regardless of the breadth of the range or the characteristic being described. [0160] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the presently disclosed subject matter belongs. Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the presently disclosed subject matter, representative methods, devices, and materials are now described. [0161] Following long-standing patent law convention, the terms “a” and “an” mean “one or more” when used in this application, including the claims. [0162] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the presently disclosed subject matter. [0163] As used herein, the term “about” and “substantially” when referring to a value or to an amount of mass, weight, time, volume, concentration or percentage is meant to encompass variations of in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1% from the specified amount, as such variations are appropriate to perform the disclosed method. [0164] As used herein, the term “substantially perpendicular” and “substantially parallel” is meant to encompass variations of in some embodiments within ±10° of the perpendicular and parallel directions, respectively, in some embodiments within ±5° of the perpendicular and parallel directions, respectively, in some embodiments within ±1° of the perpendicular and parallel directions, respectively, and in some embodiments within ±0.5° of the perpendicular and parallel directions, respectively. [0165] As used herein, the term “and/or” when used in the context of a listing of entities, refers to the entities being present singly or in combination. Thus, for example, the phrase “A, B, C, and/or D” includes A, B, C, and D individually, but also includes any and all combinations and subcombinations of A, B, C, and D. REFERENCES [0166] Andersen, S. Z., et al., “A rigorous electrochemical ammonia synthesis protocol with quantitative isotope measurements,” Nature, 2019, 570 (7762), 504-508 (“Andersen 2019”). [0167] Bao, D., et al., “Electrochemical reduction of N ₂ under ambient conditions for artificial N ₂ fixation and renewable energy storage using N ₂ /NH ₃ cycle,” Adv. Mater., 2017, 29, 1604799 (“Bao 2017”). [0168] Bolleter, W. T., et al., “Spectrophotometric Determination of Ammonia as Indophenol,” Anal. Chem., 1961, 33 (4), 592-594 (“Bolleter 1961”). [0169] Chatt, J., et al., “Recent advances in the chemistry of nitrogen fixation,” Chem. Rev., 1978, 78, 589-625 (“Chatt 1978”). [0170] Deng, J., et al., “Electrocatalytic nitrogen reduction at low temperature,” Joule, 2018, 2, 846-856 (“Deng 2018”). [0171] Eckmann, A., et al., “Probing the Nature of Defects in Graphene by Raman Spectroscopy,” Nano Lett., 2012, 12 (8), 3925-3930 (“Eckmann 2012”). [0172] Einsle, O., et al., “Nitrogenase MoFe-protein at 1.16 Å resolution: a central ligand in the FeMo-cofactor,” Science, 2002, 297, 1696-1700 (“Einsle 2002”). [0173] Erisman, J. W., et al., “How a century of ammonia synthesis changed the world,” Nat. Geosci., 2008, 1, 636-639 (“Erisman 2008”). [0174] Fei, H., et al., “Atomic cobalt on nitrogen-doped graphene for hydrogen generation,” Nat Commun, 2015, 6 (“Fei 2015”). [0175] Galloway, J. N., et al., “Transformation of the nitrogen cycle: recent trends, questions, and potential solutions,” Science, 2008, 320, 889-892 (“Galloway 2008”). [0176] Gruber, N., et al., “An Earth-system perspective of the global nitrogen cycle,” Nature, 2008, 451, 293-296 (“Gruber 2008”). [0177] Guo, D., et al., “Active sites of nitrogen-doped carbon materials for oxygen reduction reaction clarified using model catalyst,” Science, 2016, 351, 361-365 (“Guo 2016”). [0178] Hidai, M., et al., “Recent advances in the chemistry of dinitrogen complexes,” Chem. Rev.1995, 95, 1115-1133 (“Hidai 1995”). [0179] Hoffman, B. M., et al., “Mechanism of nitrogen fixation by nitrogenase: the next stage,” Chem. Rev., 2014, 114, 4041-4062 (“Hoffman 2014”). [0180] Jalilov, A. S., et al., “Asphalt-Derived High surface area activated porous carbons for carbon dioxide capture,” ACS Appl. Mater. Interfaces, 2015, 7, 1376-1382 (“Jalilov 2015”). [0181] Kandemir, T., et al., “The Haber–Bosch Process Revisited: On the real structure and stability of “ammonia iron” under working conditions,” Angew. Chem. Int. Ed., 2013, 52, 12723-12726 (“Kandemir 2013”). [0182] Kitano, M., et al., “Electride support boosts nitrogen dissociation over ruthenium catalyst and shifts the bottleneck in ammonia synthesis,” Nat. Comm., 2015, 6, 6731 (“Kitano 2015”). [0183] Lan, R. et al., “Ammonia as a suitable fuel for fuel cells,” Front. Energy Res., 2014, 2:35, 1-4 (“Lan 2014”). [0184] Ling, C., et al., “Single molybdenum atom anchored on N-Doped carbon as a promising electrocatalyst for mitrogen reduction into Ammonia at Ambient Conditions,” J. Phys. Chem. C, 2018, 122, 16842-16847 (“Ling 2018”). [0185] Liu, X., et al., “Building Up a Picture of the Electrocatalytic Nitrogen Reduction Activity of Transition Metal Single-Atom Catalysts,” J. Am. Chem. Soc., 2019, 141 (24), 9664- 9672 (“Liu 2019”). [0186] Liu, X. , et al., “Carbon-based metal-free catalysts,” Nat. Rev. Mater., 2016, 1 (11), 16064 (“Liu 2016”). [0187] Ludwinowicz, J., et al., “Potassium salt-assisted synthesis of highly microporous carbon spheres for CO ₂ adsorption,” Carbon ,2015, 82, 297-303 (“Ludwinowicz 2015”). [0188] MacKay, B. A., et al., “Dinitrogen coordination chemistry:  on the biomimetic borderlands,” Chem. Rev., 2004, 104, 385-402 (“MacKay 2004”). [0189] Milton, R. D., et al., “Nitrogenase bioelectrocatalysis: heterogeneous ammonia and hydrogen production by MoFe protein,” Energy Environ. Sci., 2016, 9, 2550-2554 (“Milton 2016”). [0190] Montoya, J. H., et al., “The Challenge of Electrochemical Ammonia Synthesis: A new perspective on the role of nitrogen scaling relations,” ChemSusChem, 2015, 8, 2180-2186 (“Montoya 2015”). [0191] Nash, J.; Yang, X., et al., “Electrochemical nitrogen reduction reaction on noble metal catalysts in proton and hydroxide exchange membrane electrolyzers,” J. Electrochem. Soc., 2017, 164, F1712-F1716 (“Nash 2017”). [0192] Rodriguez, M. M., et al., “N ₂ reduction and hydrogenation to ammonia by a molecular Iron-Potassium complex,” Science, 2011, 334, 780-783 (“Rodriguez 2011”). [0193] Scott, A., “Ammonia on route to fuel ships and planes,” Chemical Engineering New, August 12, 2020, https://cen.acs.org/energy/renewables/Ammonia-route-fuel-shi ps- planes/98/i31 (“Scott 2020”). [0194] Seh, Z. W., et al., “Combining theory and experiment in electrocatalysis: Insights into materials design,” Science, 2017, 355, eaad4998 (“She 2107”). [0195] Shi, M.-M., et al., “Au sub-nanoclusters on TiO ₂ toward highly efficient and selective electrocatalyst for N ₂ conversion to NH ₃ at ambient conditions,” Adv. Mater., 2017, 29, 1606550 (“Shi 2017”). [0196] Singh, A. R., et al., “Electrochemical ammonia synthesis—The selectivity challenge,” ACS Catal., 2017, 7, 706-709 (“Singh 2017”). [0197] Skúlason, E., et al., “A theoretical evaluation of possible transition metal electro- catalysts for N ₂ reduction,” Phys. Chem. Chem. Phys., 2012, 14 (3), 1235-1245 (“Skúlason 2012”). [0198] Smil, V., “Detonator of the population explosion,” Nature, 1999, 400, 415 (“Smil 1999”). [0199] Suryanto, B. H. R., et al., “Rational Electrode–Electrolyte Design for Efficient Ammonia Electrosynthesis under Ambient Conditions,” ACS Energy Lett., 2018, 3 (6), 1219- 1224 (“Suryanto 2018”). [0200] Tao, H., et al., “Nitrogen Fixation by Ru Single-Atom Electrocatalytic Reduction,” Chem, 2019, 5 (1), 204-214 (“Tao 2019”). [0201] Wang, A., et al., “Heterogeneous single-atom catalysis,” Nat. Rev. Chem., 2018, 2, 65- 81 (“Wang 2018”). [0202] Wang, H., et al., “Review on recent progress in nitrogen-doped graphene: Synthesis, characterization, and its potential applications,” ACS Catal., 2012, 2, 781-794 (“Wang 2012”). [0203] Watt, G. W., et al., “Spectrophotometric Method for Determination of Hydrazine,” Anal. Chem., 1952, 24 (12), 2006-2008 (“Watt 1952”). [0204] Yandulov, D. V., et al., “Catalytic reduction of dinitrogen to ammonia at a single molybdenum center,” Science, 2003, 301, 76-78 (“Yandulov 2003”). [0205] Yang, X.-F., et al., “Single-atom catalysts: A new frontier in heterogeneous catalysis,” Acc. Chem. Res., 2013, 46, 1740-1748 (“Yang 2013”). [0206] Zhang, C, et al., “Single-Atomic Ruthenium Catalytic Sites on Nitrogen-Doped Graphene for Oxygen Reduction Reaction in Acidic Medium,” ACS Nano, 2017, 11 (7), 6930- 6941 (“Zhang 2017”).