A PROCESS FOR GROWING A FILM OF A METAL-CARBON NANOMATERIAL COMPOSITE WITH ID, 2D, OR 3D STRUCTURE AND/OR A MIXTURE THEREOF ON

A METAL SUBSTRATES

The present disclosure claims priority to the earlier International Application No. PCT/IB2021/051792, filed March 4, 2021, the entire disclosure of which is incorporated into the present disclosure by way of reference.

FIELD OF INVENTION

The present disclosure relates to a process for growing a film of a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal and a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a mixture thereof on a metal substrate, particularly when said process involves electrochemical reduction.

BACKGROUND OF THE INVENTION

Due to their superior properties, such as high electrical and thermal conductivity and chemical inertness, nanocarbon films find their applications in various fields of coating, such as solar cells, electronics, and biomaterial coatings. Coating nanocarbon films upon a metallic substrate is a subject of particular challenge due to the unstable adhesion of the carbon film onto the substrate. Conventionally, this problem is addressed by way of decomposing organic molecules in order to carry out the coating. However, these processes require high energy.

For example, the Canadian patent publication No. CA2527124A1 describes a process for producing an ultraflat nanocrystalline diamond thin film by laser ablation which includes creating atomic hydrogen and a supersaturated state of carbon in a space between a target and a substrate in a hydrogen atmosphere inside a reaction chamber at the substrate temperature of 450 - 650 °C. Further example is the U.S. patent publication No. US2005/0031785A1 which teaches a process to form pure nanocrystalline carbon film on a substrate at a temperature less than about 500 °C using nanocrystalline diamond powder as a seed and microwave plasma for enhancing the performance of the chemical vapor deposition (CVD) of hydrocarbon gases. Next, the U.S. patent No. US 9159924 B2 shows a method of coating the carbon films on the substrate by means of the decomposition of the polymer coating layer at 2,500 °C.

Additionally, Wu et al. [Wu 2021] reported an electrochemical process which converts chloroacetic acid into a diamond-like carbon film (DLC film) deposited upon a fluorine-doped tin oxide (FTO) glass, which is a cathode. Wu 2021 achieved the carbon deposition time of less than one hour and the applied voltage of 3 V at ambient conditions. However, the carbon films obtained from said process are amorphous carbon films which have significantly inferior performance than nanocrystalline carbon films, and thus are unsuitable for many applications such as electronics. The process according to Wu 2021 is also not applicable to a metallic substrate.

Thus, there is a demand for a process that requires substantially less energy for forming a nanocarbon film having a crystalline structure on various metallic substrates, and thus are suitable for various fields of applications.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a new process for coating a film of carbon nanomaterial, and their variants, on a metal substrate. The inventor has found that embodiments according to the concept of the present invention enable the production of such products at a significantly less energy-intensive condition.

In the first, second and third aspects, the present invention provides a new process for forming, upon at least one electrode, a film of a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and/or a mixture thereof. The embodiments’ characterizing features, involving simultaneous electrochemical reduction of an oxygenic organic compound and a metallic cation in presence of an electrolyte and said at least one electrode, allow said process to be carried out under ambient conditions and at an onset potential not greater than 10 Volt. Said conditions, which simplify the production, are effects that distinguishes a process in accordance with the present invention from the currently available ones. In these aspects, the electrode upon which the film of carbon nanomaterial is formed is considered a substrate, and the formation of carbon nanomaterial is the intended coating. Due to the simplicity of the process as explained above, it is conducive to scaling up for coating a large metallic substrate. The thickness of metal-carbon nanomaterial composite film per a single run of an embodiment is approximately 1 - 10 microns, depending on the type of metal substrate, the type and concentration of a metallic cation, the type and concentration of an oxygenic organic compound, the type and concentration of an ionic conductive salt, and reaction time of a batch.

An embodiment in accordance with the first aspect is a process for forming, upon at least one electrode, a film of a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and/or a mixture thereof. Said process is carried out by electrochemically reducing an oxygenic organic compound and a metallic cation simultaneously. The electrochemical reduction takes place under ambient conditions at an onset potential not greater than 10 Volt in presence of an electrolyte and said at least one electrode. Said electrode comprising a metallic material, said metallic material being one or more of the following: a post-transition element, a transition element, and an alloy thereof.

An embodiment in accordance with the second aspect is a process for forming, upon a cathode, a film of a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and/or a mixture thereof. Said process comprises a step of electrochemically reducing an oxygenic organic compound and a metallic cation simultaneously in presence of an electrolyte that is separated into an anolyte and a catholyte, an anode submerged in said anolyte, and said cathode submerged in said catholyte. Said catholyte comprises a mixture of l-butyl-3- methylimidazolium tetrafluoroborate ([bmim][BF4]), ammonium sulfate ((NFL ₂ SO ₄ ) or sodium sulfate (Na ₂ S0 ₄ ), a metallic cation precursor, said oxygenic organic compound, and water. Said simultaneous electrochemical reduction of the oxygenic organic compound and the metallic cation occurs under ambient conditions at an onset potential not greater than 10 Volt.

An embodiment in accordance with the third aspect is a process for forming, upon a cathode, a film of a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and/or a mixture thereof. Said process comprises a step of electrochemically reducing an oxygenic organic compound and a metallic cation simultaneously in presence of an electrolyte, an anode and said cathode submerged in said electrolyte. Said electrolyte comprises a mixture of 1-butyl- 3-methylimidazolium tetrafluoroborate ([bmim][BF4]), ammonium sulfate ((NFL ₂ SO ₄ ) or sodium sulfate (NaiSC ), a metallic cation precursor, said oxygenic organic compound, and water. Said simultaneous electrochemical reduction of the oxygenic organic compound and the metallic cation occurs under ambient conditions at an onset potential not greater than 10 Volt.

In an embodiment, the oxygenic organic compound is dissolved in the electrolyte. In such case, it is preferable that the oxygenic organic compound is dissolved in the electrolyte at a concentration within a range of 0.1 to 10 M.

Thus, it is preferable that the oxygenic organic compound is water-soluble. Preferred oxygenic organic compounds include: an alcohol, polyol, carboxylic acid, ketone, aldehyde, and carbamate.

Optionally, said at least one electrode, which in some embodiments a cathode, is a metallic foil. Preferably, said metallic foil consists essentially of: the post-transition element that is selected from bismuth (Bi) and tin (Sn); or the transition element that is selected from silver (Ag), copper (Cu), and gold (Au); or stainless steel.

Preferably, the electrolyte or the catholyte is a mixture containing an ionic conductive salt, a metallic cation precursor, an oxygenic organic compound, and water. Preferably, the concentration of said ionic conductive salt in the electrolyte or the catholyte is within a range of 0.01 to 10 M.

Preferably, said ionic conductive salt comprises a cation that is selected from alkaline metal cation, ammonium cation, and imidazolium cation, or a mixture thereof. Preferably, said alkaline metal cation is sodium cation (Na ⁺ ). Preferably, said ammonium cation is ammonium cation (NH4 ⁺ ). Preferably, said imidazolium cation is 1 -butyl-3 -methylimidazolium ([bmim]).

Preferably, said ionic conductive salt comprises an anion that is selected from the group comprising tetrafluoroborate (BFT), hexafluorophosphate (PF ₆ ), halides (CF, Br , F , G), hexafluoroantimonate (SbF ₆ ), sulfate (SO4 ² ) and nitrate (NO3 ).

Preferably, said metallic cation precursor comprises the post-transition element or the transition element. More preferably, the concentration of said metallic cation precursor is within a range of 0.0001-1 M. Also more preferably, said metallic cation precursor is water soluble. Even more preferably, said metallic cation precursor is silver nitrate (AgNOi) or bismuth (III) nitrate (Bi(N03)3).

Preferably, the film is formed at a growth rate that is within a range of 2-20 microns per hour.

In the fourth and fifth aspects, the present invention provides an improved product that is obtainable from the abovementioned first, second, or third aspect. An embodiment in accordance with the fourth aspect is a film of nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal. Said product is obtainable from any embodiment in accordance with the first, second, or third aspect.

Preferably, said film comprises a graphitic carbon.

Also preferably, said film has a thickness within a range of 1-10 microns.

An embodiment in accordance with the fifth aspect is a film that is a mixture having various carbon structures comprising: a nanocrystalline diamond, an amorphous carbon, a graphitic carbon, and a metal-carbon nanomaterial composite, said composite containing a post transition metal or a transition metal. Said product is obtainable from any embodiment in accordance with the first, second, or third aspect.

Preferably, the various carbon structures further comprise a graphite or a graphene.

Accordingly, the present disclosure provides examples to illustrate the conditions of such processes and the characteristic properties of such products. The preferred embodiments will be described in detail later on.

BRIEF DESCRIPTION OF DRAWINGS

Fig 1 shows a schematic diagram of an electrochemical cell for electrochemically reducing an oxygenic organic compound and a metallic cation simultaneously in accordance with a preferred embodiment (not to scale).

Fig 2 shows a schematic diagram of an electrochemical cell for electrochemically reducing an oxygenic organic compound and a metallic cation simultaneously in accordance with an alternative embodiment (not to scale).

Fig 3 A shows a Raman spectrum exhibiting merged peaks of a product of Example 1.

Fig 3B shows an Atomic Force Microscopy (AFM) image of a product of Example 1.

Fig 4 A shows a Raman spectrum exhibiting merged peaks of a product of Example 2.

Fig 4B shows an Atomic Force Microscopy (AFM) image of a product of Example 2.

Fig 5 shows a Raman spectrum exhibiting merged peaks of a product of Example 3.

Fig 6 shows a Raman spectrum exhibiting merged peaks of a product of Example 4.

Fig 7 shows a Raman spectrum exhibiting merged peaks of a product of Example 5.

Fig 8 shows a Raman spectrum exhibiting merged peaks of a product of Example 6.

Fig 9 shows a Raman spectrum exhibiting merged peaks of a product of Example 7. Fig 10 shows a Raman spectrum exhibiting merged peaks of a product of Example 8.

Fig 11 shows a Raman spectrum exhibiting merged peaks of a product of Example 9.

Fig 12 shows a Raman spectrum exhibiting merged peaks of a product of Example 10.

Fig 13 shows a Raman spectrum exhibiting merged peaks of a product of Example 11.

Fig 14 shows a Raman spectrum exhibiting merged peaks of a product of Example 12.

Fig 15 shows a Raman spectrum exhibiting merged peaks of a product of Example 13.

Fig 16 shows a Raman spectrum exhibiting merged peaks of a product of Example 14.

Fig 17 shows a Raman spectrum exhibiting merged peaks of a product of Example 15.

Fig 18 shows a Raman spectrum exhibiting merged peaks of a product of Example 16.

Fig 19 shows a Raman spectrum exhibiting merged peaks of a product of Example 17.

Fig 20 shows a Raman spectrum exhibiting merged peaks of a product of Example 18.

Fig 21 shows a Raman spectrum exhibiting merged peaks of a product of Example 19.

Fig 22 shows a Raman spectrum exhibiting merged peaks of a product of Example 20.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

It is to be understood that the following detailed description will be directed to embodiments, provided as examples for illustrating the concept of the present invention only. The present invention is in fact not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of this invention will be limited only by the appended claims.

The detailed description of the invention is divided into various sections only for the reader’s convenience and disclosure found in any section may be combined with that in another section.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

The term “about” when used before a numerical designation, e.g., dimensions, time, amount, and such other, including a range, indicates approximations which may vary by ( + ) or ( - ) 10 %, 5 % or 1 %, or any sub-range or sub-value there between. “Comprising” or “comprises” is intended to mean that the compositions and processes include the recited elements, but not excluding others. “Consisting essentially of’ when used to define compositions and methods, shall mean excluding other elements of any essential significance to the combination for the stated purpose. Thus, a process or product consisting essentially of the elements as defined herein would not exclude other materials or steps that do not materially affect the basic and novel characteristic(s) of the claimed invention. “Consisting of’ shall mean excluding more than trace elements of other ingredients and substantial steps. Embodiments defined by each of these transition terms are within the scope of this invention.

“Oxygenic organic compound” is intended to mean a mono-molecular organic compound having an oxygen atom.

Electrochemical cell

Fig 1 shows a schematic diagram of an electrochemical cell in which a process for forming a film of carbon nanomaterial is conducted in accordance with a preferred embodiment. The electrochemical cell (10) comprises a receptacle (100) and a membrane (200) which separates the receptacle (100) into an anode region (300) and a cathode region (400). The receptacle (100) receives and contains an electrolyte which is in turn separated by the membrane (200) into an anolyte (310) and a catholyte (410) contained in the anode region (300) and the cathode region (400), respectively. This arrangement allows options whereby the anolyte (310) and the catholyte (410) are either the same or different substances. Further, this preferred electrochemical cell (10) is a 3-electrode system wherein electrodes (320, 420, 430) are immersed in, and thus in a direct contact with, the electrolyte (310, 410). In the anode region (300), the electrode is an anode (320). The anode region (300) further comprises a vent (350) to provide a passage of oxygen out from the anode region (300). Preferably, the vent (350) is located at the upper part or top of the anode region (300). In the cathode region (400), the electrodes comprise a cathode (420) and a reference electrode (430). The cathode region (400) further comprises a vent (450) to provide a passage of gas byproduct out from the cathode region (400). Preferably, the vent (450) is located at the upper part or top of the cathode region (400). The electrodes (320, 420, 430) are electrically connected to a power supply (500), which according to a preferred embodiment is a source of direct current electricity.

Fig 2 shows a schematic diagram of an electrochemical cell in which a process for forming a film of carbon nanomaterial is conducted in accordance with an alternative embodiment which does not feature the membrane (200). Thus, the anode and cathode regions (300, 400) which in Fig 1 were separated and defined by the membrane (200), along with the anolyte and catholyte (310, 340) which in Fig 1 were defined by the cathode and anode regions (300, 400), are not present in Fig 2. In this alternative embodiment, the receptacle (100) contains an electrolyte (110) that is a mixture of an ionic conductive salt, a metallic cation precursor, an oxygenic organic compound, and water. The other components of the alternative embodiment, as well as their characteristics, connections and reference numbers, are substantially similar to those of the preferred embodiment previously shown and described with respect to Fig 1.

Oxygenic organic compound

According to the present invention, the carbon source comprises an oxygenic organic compound. Preferably, the oxygenic organic compound is water soluble. More preferably, the oxygenic organic compound is an alcohol, polyol, aldehyde, carboxylic acid, ketone, or carbamate. In addition, the oxygenic organic compound may be supplied to the electrolyte in any desired form, for example, in solid, liquid, gaseous, or solvated form. Preferably, the oxygenic organic compound is dissolved in the electrolyte (i.e. supplied in the solvated form).

Pressure

A process according to the concept of the present invention may be carried out in various conditions which may be adjusted according to the circumstantial requirements. The applicable pressure is within a range of about 1 to about 20 atm.

The pressure in accordance with an embodiment is an ambient pressure. The ambient pressure refers to a common or usual condition surrounding any person in a room. An ambient pressure for operating the process is preferably 1 atm. Because a process in accordance with an embodiment allows the electrochemical reduction to occur effectively at such ambient pressure, it obviates the need to pressurize, depressurize, vacuumize or control the pressure at any part of the electrochemical cell (10) and thus substantially simplifies the production.

Temperature

A process according to the concept of the present invention may be carried out in various conditions which may be adjusted according to the circumstantial requirements. The applicable temperature is within the range from about 10 °C to about 60 °C.

The temperature in accordance with an embodiment is an ambient temperature. The ambient temperature refers to a common or usual condition surrounding any person in a room. Preferably, the ambient temperature is within a range of about 15 °C to about 50 °C. More preferably, the ambient temperature is about 30 °C. Because a process in accordance with an embodiment allows the electrochemical reduction to occur effectively at such ambient temperature, it obviates the need to heat, cool or control the temperature at any part of the electrochemical cell (10) and thus substantially simplifies the production.

Onset potential

Generally, the onset potential of the electrochemical cell (10) is at least of the electric potential sufficient to initiate the simultaneous electrochemical reduction of an oxygenic organic compound and a metallic cation. Preferably, the onset potential across the electrodes (320, 420, 430) is substantially constant during the electrochemical reduction.

The onset potential of the electrochemical cell (10) depends on the electrode being selected. In an embodiment, the electrochemical cell (10) comprises a power supply (500) to provide the onset potential, which is preferably within a range of about 0.1 to about 10 V, more preferably within a range of about 0.9 to about 3 V, and even more preferably at about 1.6 V.

Preferably, the power supply (500) is adapted to monitor the onset potential. Even more preferably, the power supply (500) is adapted to regulate the onset potential to be in accordance with a preset value. In the following Examples, the power supply (500) is a potentiostat which is capable of both monitoring and regulating the onset potential. A potentiostat’ s equivalent devices for an industrial scale production include a rectifier which is as well applicable to the concept of the present invention.

Electrolyte

According to the concept of the present invention, an electrolyte, which may be separated into an anolyte (310) and a catholyte (410), is an ion-containing fluid. Preferably, the anolyte (310) is an aqueous electrolyte and the catholyte (410) is a mixture containing an ionic conductive salt, a metallic cation precursor, an oxygenic organic compound, and water. Optionally, the anolyte (310) and the catholyte (410) are the same electrolyte, which is a mixture of an ionic conductive salt, a metallic cation precursor, an oxygenic organic compound, and water.

According to the concept of the present invention, all known ionic conductive salts may be part of the mixture that forms the electrolyte. Preferably, the ionic conductive salt in an embodiment are compounds represented by Formula (I):

[A]n ⁺ [Y]„- - (I) wherein: n is 1 or 2; [Y] _n is selected from the group comprising tetrafluoroborate ([BF4] ), hexafluorophosphate ([PF ₆ ] ), halides (Cl , Br , F , G), hexafluoroantimonate ([SbF ₆ ] ), sulfate ([SO4 ² ]) and nitrate ([NO3] );

[A] ⁺ is selected from —

(a) the group comprising alkali metal cations, ammonium cations represented by Formula

(II):

R ¹ , R ² , R ³ , and R ⁴ being selected from hydrogen atom, Cl-C6-alkyl, Cl-C6-alkoxy, Cl- C6-aminoalkyl, C5-C12-aryl, and C5-C12-aryl-Cl-C6-alkyl groups; and

(b) the group comprising imidazolium cations represented by Formula (III):

R, R ¹ , and R ² being selected from Cl-C6-alkyl, Cl-C6-alkoxy, Cl-C6-aminoalkyl, C5- C12-aryl, and C5-C12-aryl-Cl-C6-alkyl groups.

According to an embodiment, the preferred combination of the ionic conductive salt, the oxygenic organic compound, the metallic cation precursor, and water, is as follows: the ionic conductive salt being l-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), ammonium sulfate ((NFL iSCC), sodium sulfate (NaiSCC), or a mixture thereof, the metallic cation precursor being silver nitrate (AgNOi) or bismuth (III) nitrate (Bi(N0 ₃ ) ₃ ), the oxygenic organic compound, and water.

In some embodiments, the ionic conductive salt also functions as a stabilizer of the carbon nanomaterial film formed at the at least one electrode during the simultaneous electrochemical reduction of the oxygenic organic compound and the metallic cation in the electrochemical cell (10). Preferably, the ionic conductive salt is selected from ([bmim][BF4]), (NH4)2S04, Na2S04, and a mixture thereof.

According to the concept of the present invention, the anolyte may also be an aqueous solution. Preferably, the anolyte that is an aqueous solution comprises a salt as a solute and water as a solvent. According to an embodiment, the preferred aqueous solution contains a cation comprising Na ⁺ , K ⁺ , or Cs ⁺ and an anion comprising HCO3 , SO4 ² , or Cl .

In some embodiments, the anolyte is an aqueous solution of potassium bicarbonate (KHCO3).

Membrane

In the present disclosure, a membrane (200) is present to separate the receptacle (100) into an anode region (300) and a cathode region (400), and thus the electrolyte into the anolyte (310) and the catholyte (410), in order to prevent oxidation of the carbon nanomaterial in the electrolyte (310, 410). The membrane (200) further prevents the gaseous anodic products, such as oxygen, from mixing with the gaseous cathodic products, such as hydrogen, thereby enhancing the transportation of proton (H ⁺ ) from the anode region (300) to the cathode region (400). Preferably, the membrane (200) arranged thus causes the contents of the two regions (300, 400) to have different pH conditions.

In one embodiment, the membrane (200) comprises a polymer film. Preferably, the membrane (200) is a proton-conductive membrane made of a polymer film which allows the transportation of proton only. Preferred examples of such proton-conductive membrane include those commercially available under the tradename of NAFION™, specifically NAFION™ 961, NAFION™ 430, or NAFION™ 117.

Electrode

According to an embodiment, an electrode in the electrochemical cell (10) is categorized into a cathode (420), and/or an anode (320). The cathode (420) is an electrode having more negative potential than the other electrode, while the anode (320) is an electrode having less negative potential than the other electrode.

Preferably, at least one electrode upon which the film of carbon nanomaterial is formed consists essentially of a metallic material, comprising one or more of the following: a post transition element, a transition element, and an alloy thereof. Preferably, said electrode is a cathode (420). Preferably, said electrode is a metallic foil. More preferably, said metallic foil comprises one or more of the post-transition element and the transition element. Even more preferably, said metallic foil is a bismuth (Bi) foil, tin (Sn) foil, silver (Ag) foil, copper (Cu) foil, gold (Au) foil, or stainless steel foil.

Preferably, the anode (320) is a platinum foil, platinum mesh, platinum rod, or graphite rod. More preferably, the anode (320) is a platinum foil or platinum mesh.

In some embodiments, the electrochemical cell further comprises a reference electrode (430) to provide a 3-electrode cell system. Preferably, the reference electrode (430) is an Ag/AgCl electrode.

Reaction time

According to an embodiment, the electrochemical reduction occurs in the electrochemical cell (10) as a batch operation. The crystal structure and crystal size of the resulting product depends on the nature of electrode used, the energy supplied, and the reaction time, among others. Prolonging the reaction time results in a larger crystallite size being formed. According to the embodiments, the crystallite size is measured by Raman peaks.

According to the embodiments, the reaction time for each batch of production can be ranged from about 5 minutes to 140 minutes. Preferably, the reaction time for each batch of production is about 15 minutes to 75 minutes.

In an embodiment, the process of forming a film of metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a mixture thereof on metal substrates, in the electrochemical cell (10) is preferably carried out as a batch operation.

The metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a mixture thereof is formed at at least one electrode. Preferably, said product is formed at the cathode (420).

The metal-carbon film product obtained from a process in accordance with a preferred embodiment comprises a graphite and/or a graphene and/or a graphitic and/or the nanocrystalline diamond and/or the amorphous carbon, said composite also containing the post-transition metal or the transition metal, and/or the mixture thereof.

The abovementioned process results in a film of metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a mixture thereof, which is a mixture having various carbon structures. Said structures are inclusive of, and selectable from: an amorphous carbon, a graphite, a graphene, a nanocrystalline diamond, and a post-transition metal or a transition metal.

Examples of embodiment

Twenty Examples were carried out for the embodiments. In all of the Examples, the following paragraphs apply.

Electrochemical reductions took place in a three-electrode cell system at a pressure of about 1 atm. and at a temperature of about 30 ± 5 °C. If a membrane (200) was used for separating the electrolyte (110) into the anolyte (310) and the catholyte (410), said membrane was NAFION™ 117; and if a reference electrode (430) was used, said reference electrode was Ag/AgCl with a 3.5 mol/L potassium chloride (KC1) solution. The carbon source was mixed with the electrolyte (110) or the catholyte (410), as the case may be. The electrochemical reduction’s onset potentials were measured by a potentiostat. After the reaction time, the film of carbon nanomaterial product was formed at the cathode (420), which was then removed from the electrolyte (110) or the catholyte (410), as the cases may be, and dried.

Further, where an amine solution was saturated with carbon dioxide gas (CO2), such saturation was carried out in order to prepare a carbamate. In such case, CO2 was purged through the amine solution at ambient conditions. The flow rate of CO2 per volume of amine solution was within a range of 0.04 - 40 cm ³ CCh/cm ³ amine solution per minute, and the purging time was within a duration of 1-1,000 minutes.

Moreover, the cathodes (420) in the Examples were metallic foils. Where the cathode (420) was a stainless steel foil, the stainless steel material was Grade SS316, comprising approximately 67.75 % iron (Fe), 17.5 % chromium (Cr), 11.5 % nickel (Ni), 2.25 % molybdenum (Mo), 1 % manganese (Mn) by weight, and insignificant amount of carbon (C) and other non-metallic elements.

Table 1 in the next two sheets shows the particulars of Examples 1-20. Description of the product obtained from each Example shall follow Table 1.

Example 1 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 3A, said film product comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures. Also, according to the Atomic Force Microscopy (AFM) image shown in Fig. 3B, wherein the dark area represents the substrate/cathode (420) and the light area represents the film of metal-carbon composite, the film had the thickness of 2-6 microns. It should be noted that the said thickness was measured at the transition region area between substrate/cathode (420) and the film. Accordingly, the film product’s growth rate was 4 - 12 microns per hour.

Example 2 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 4A, said film product comprised nanocrystalline diamond and graphitic carbon. Also, according to the Atomic Force Microscopy (AFM) image shown in Fig. 4B, wherein the dark area represents the substrate/cathode (420) and the light area represents the film of metal-carbon composite, the film had the thickness of 2 - 6 microns. Accordingly, the film product’s growth rate was 4 - 12 microns per hour.

Example 3 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 5, said film product comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures.

Example 4 produced, upon the substrate which was the cathode (420) a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 6, said film product comprised nanocrystalline diamond, graphitic carbon, graphene and amorphous carbon structures

Example 5 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 7, said film product comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures.

Example 6 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 8, said film product comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures. Example 7 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 9, said film product comprised amorphous carbon, graphitic and graphite carbon structures.

Example 8 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 10, said film product comprised amorphous carbon, graphitic and graphite carbon structures.

Example 9 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 11, said film product comprised graphitic carbon and amorphous carbon structures.

Example 10 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 12, said film product comprised metastable diamond, graphitic carbon, and amorphous carbon structures.

Example 11 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 13, said film product comprised graphitic carbon and amorphous carbon structures.

Example 12 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 14, said film product comprised graphitic carbon and amorphous carbon structures.

Example 13 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 15, said film product comprised graphitic carbon and amorphous carbon structures.

Example 14 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 16, said film product comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures. Example 15 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 17, said film product comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures.

Example 16 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 18, said film product comprised nanocrystalline diamond, metastable diamond, graphitic carbon, and amorphous carbon structures.

Example 17 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Bi and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 19, said film product comprised graphitic carbon and amorphous carbon structures.

Example 18 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 20, said film product comprised nanocrystalline diamond, graphitic carbon, graphene and amorphous carbon structures.

Example 19 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 21, said film product comprised nanocrystalline diamond, metastable diamond, graphitic carbon, and amorphous carbon structures.

Example 20 produced, upon the substrate which was the cathode (420), a film of metal- carbon composite product in the form of metallic Ag and nanocrystalline carbon with a ID, 2D, and 3D structure. According to the Raman spectrum in Fig. 22, said film product comprised nanocrystalline diamond, metastable diamond, graphitic carbon, and amorphous carbon structures.

References

[Wu 2021] Effect of carbon chain length of chlorinated carboxylic acids on morphology of the carbon films electrodepo sited from aqueous solutions, Wu et al., Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2021, 626; List of Drawing References

100 receptacle

110 electrolyte

200 membrane 300 anode region

310 anolyte 320 anode 350 vent 400 cathode region 410 catholyte

420 cathode 430 reference electrode 440 feed 450 vent 500 power supply