FIELD OF THE INVENTION

The present invention relates to the field of harvesting electricity from surrounding ambient heat using organic electrochemical device.

The present invention on electricity harvesting is based on reversible organic electron transfer reactions between organic donors and acceptors or Ti02 acceptor and organic donors which take place at 28 °C to 40 °C.

The present invention on electricity harvesting is based on reversible organic electron transfer reactions between organic donors such as tertiary amines, amides and sulfoxides and acceptors such as -chloranil, quinone, diamide and sulfone derivatives or Ti0 ₂ acceptor and organic donors which take place at 28°C to 40 °C.

The organic electrochemical cells constructed as per the present invention have potential for producing electricity using solar heat energy stored in readily accessible materials like concentrated NaOH for producing ambient heat (28°C to 40°C) for 24x7 electricity production for Household, Grid, Automobile and Air Cooling applications.

BACKGROUND OF THE INVENTION

Harvesting electricity from solar energy is a very important contemporary research area in this time of escalating oil price, depleting fossil fuel resources and threat of climate change crisis. There have been sustained efforts on the development of various types of solar cells using organic compounds as such devices require relatively simple processing. For instance, there have been immense research efforts for the last 3 decades on the development of dye sensitized solar cells (DSSC), perovskite solar cells and organic (or polymer) solar cells. In organic (or polymer) solar cells, excitation of electron in the donor followed by electron transfer to the acceptor give radical cation and anions as charge carriers which upon transport to the electrodes lead to production of electricity.

Although, there have been numerous reports for over more than 50 years that radical cation and anion intermediates are readily formed from organic donors like amines and even electron rich hydrocarbons and acceptors like p-chloranil and are in equilibrium with the corresponding charge transfer (CT) complexes, surprisingly there was no report so far on the development of electrochemical cell that would lead to harvesting of electricity from these charge carriers formed in the ground states utilizing the surrounding ambient heat energy.

The inventors of the present invention have constructed electrochemical cells with different configurations that harvest electricity from surrounding heat (28 °C to 40 °C ) using A1 foil and Graphite sheet electrodes, coated with the Ti0 ₂ and polyethylene oxide paste, with p-chloranil (C1 ₄ BQ) and tertiary amine derivatives like diisopropyl ethylamine or amides like diisopropylbenzamide or organic sulfoxides like the widely used inexpensive dimethyl sulfoxide as donors and -benzoquinone, N-alkylphthalimides and aryl and alkyl sulphone derivatives as electron transporting agents.

The inventors of the present invention have also constructed electrochemical cells using A1 foil and Graphite sheet electrodes, coated with the Ti0 ₂ and polyethylene oxide and tertiary amine derivatives like diisopropyl ethylamine or amides like diisopropylbenzamide or organic sulfoxides pastes without using p-chloranil (C1 ₄ BQ).

OBJECTIVE OF THE INVENTION

An objective of the present invention is to provide a device for harvesting electricity from surrounding ambient heat using organic electrochemical cell. Another objective of the present invention is to provide a device for harvesting electricity which is based on reversible organic electron transfer reactions between organic donors and acceptors or Ti0 ₂ acceptor and organic donors which take place at 28°C to 40°C.

Yet another objective of the present invention is to provide a device for harvesting electricity which is based on reversible organic electron transfer reactions between organic donors such as tertiary amines, amides and sulfoxides and acceptors such as p- chloranil, -benzoquinone, diamide and sulfone derivatives or Ti0 ₂ acceptor and organic donors which take place at 28°C to 40°C.

Still another objective of the present invention is to provide a device for harvesting electricity by using the inexpensive />-chloranil which has very high electron affinity.

Still another objective of the present invention is to provide a device for harvesting electricity for producing ambient heat (28°C to 40°C) for 24x7 electricity production for Household, Grid, Automobile and Air Cooling applications.

SUMMARY OF THE INVENTION

The present invention provides a device for harvesting electricity from surrounding ambient heat using organic electrochemical cell.

In another embodiment, the present invention provides a device for harvesting electricity which is based on reversible organic electron transfer reactions between organic donors and acceptors or Ti0 ₂ acceptor and organic donors which take place at 28°C to 40°C. In yet another embodiment, the present invention provides a device for harvesting electricity which is based on reversible organic electron transfer reactions between organic donors such as tertiary amines, amides and sulfoxides and acceptors such as p- chloranil, quinone, diamide and sulfone derivatives or Ti0 ₂ acceptor and organic donors which take place at 28°C to 40°C.

In still another embodiment, the present invention provides a device the construct of which is based on layering technology as given below:

a. layer containing SS material or graphite sheet,

b. acceptor layer,

c. donor layer,

d. optionally another acceptor layer, and

e. layer containing Aluminium material.

In still another embodiment, the present invention provides a device the construct of which further contains a metal oxide layer between the layer containing SS material or graphite sheet and the acceptor layer.

In still another embodiment, the present invention provides a device which further contains a metal oxide layer between the layer containing aluminum sheet and the acceptor layer / donor layer.

Still another embodiment, the present invention provides a device for harvesting electricity by providing ambient heat (28°C to 40°C) for 24x7 electricity production for Household, Grid, Automobile and Air Cooling applications. DESCRIPTION OF THE DRAWINGS:

Figure 1: >-Chloranil acceptor and some electron donors.

Figure 2. (a) Harvesting electricity based on ground state electron transfer reactions (b) Schematic diagram of two layer configuration using A1 and SS or Gr electrodes (c) Representative I-V curve for the two layer cell (DIPEA donor).

At 28 C, With SS Foil Cathode With Graphite Cathode

DIPEA Pmax 0.756mW/FF 0.263 Pmax 1.415 mW/FF 0.235

DABCO Pmax 0.665mW/FF 0.233 Pmax 0.139 mW/FF 0.194

TPA Pmax 0.306mW/FF 0.254 Pmax 0.794 mW/FF 0.240

Figure 3. (a) Schematic diagram of multi-layer with Cl ₄ BQ/donor/PC/PEO configuration and (b) Representative I-V curve for the cell (DABCO donor) (c) Schematic diagram of multi-layer with Cl ₄ BQ/donor/PC/Ti0 ₂ /PEO configuration (d) Representative I-V curve for the cell (DIPEA donor).

(a) (c)

1 h after packing 48 h after packing 1 h after packing 48 h after packing (28 °C) (28 °C) (28 °C) (28 °C)

Donor Pmax/mW/FF Pmax/mW/FF Pmax/mW/FF Pmax/mW/FF(

TMPDA 1.176/0.221 0.373/0.202 2.855/0.235 1.449/0.235

TPA 0.889/0.269 0.273/0.251 0.306/0.242 0.109/0.236

DABCO 2.986/0.208 1.553/0.246 4.846//0.189 0.963/0.243

DIPEA 1.724/0.240 1.648/0.297 7.483/0.271 1.833/0.308

1 h after packing 48 h after packing 1 h after packing 48 h after packing (40 °C) (40 °C) (40 °C) (40 °C)

Donor Pmax/mW/FF Pmax/mW/FF Pmax/mW/FF Pmax/mW/FF(

TMPDA 1.469/0.272 0.790/0.309 3.099/0.261 1.822/0.250

TPA 1.333/0.255 0.428/0.285 0.375/0.245 0.142/0.256

DABCO 5.492/0.313 2.320/0.267 6.155/0.206 1.216/0.249

DIPEA 5.695/0.296 2.228 /0.347 8.147/0.347 2.057/0.334

Figure 4 (a) Schematic diagrams of multi-layer cell using BQ along with /;-chloranil without Ti0 ₂ in PC layer (b) Representative I-V curves for the cell (DABCO donor) (c) Multilayer cell using BQ along with -chloranil with Ti0 ₂ in PC layer (d) Representative

I-V curves for the cell (DIPEA donor).

(a) (c)

1 h after packing 48 h after packing 1 h after packing 48 h after packing (28 °C) (28 °C) (28 °C) (28 °C)

Donor Pmax(mW)/FF Pmax(mW)/FF Pmax(mW)/FF Pmax(mW)/FF

TMPDA 1.448/0.338 0.544/0.197 0.926/0.235 0.663/0.208

TPA 1.453/0.220 0.882/0.209 0.706/0.209 0.450/0.197

DABCO 2.972/0.251 1.668/0.239 3.544/0.368 2.387/0.301

DIPEA 5.909/0.182 1.550/0.202 7.788/0.288 5.816/0.269

1 h after packing 48 h after packing 1 h after packing 48 h after packing (40 °C) (40 °C) (40 °C) (40 °C)

Donor Pmax(mW)/FF Pmax(mW)/FF Pmax(mW)/FF Pmax(mW)/FF

TMPDA 2.175/0.276 1.205/0.273 I.614/0.282 1.299/0.263

TPA 1.752/0.240 1.216/0.240 0.939/0.219 0.728/0.219

DABCO 5.391/0.391 3.023/0.399 4.806/0.432 3.776/0.434

DIPEA 8.229/0.229 2.074/0.231 I I.74/0.296 8.338/0.394

Figure 5. (a) Schematic diagram of multi-layer with Ti0 ₂ /donor without C1 BQ (b) Representative I-V curves for the cell (DIPBA donor).

1 h after packing 48 h after packing

Donor Pmax/mW/FF Pmax/mW/FF

(28°C) (28°C)

TPA 0.004/0.277 0.002/0.279

DABCO 0.002/0.279 0.011/0.114

DIPEA 0.004/0.289 0.004/0.295

1 h after packing 48 h after packing

Donor Pmax/mW/FF Pmax/mW/FF

(40°C) (40°C)

TPA 0.004/0.270 0.003/0.287

DABCO 0.026/0.092 0.019/0.136

DIPEA 0.005/0.281 0.005/0.305

Figure 6. (a) Schematic diagram of multi-layer cell with metal oxide in edge layers without donor (b) Multi-layer cell with metal oxide in edge layers and also in PC layer without donor (c) Representative I-V curves for the cell (Ti0 ₂ donor), (d) Representative I-V curves for the cell (Ti0 ₂ donor).

(a) (b) 1 h after packing 48 h after packing 1 h after packing 48 h after packing (28 °C) (28 °C) (28 °C) (28 °C)

MxOy Pmax/mW/FF Pmax/MW/FF) Pmax/MW/FF Pmax/MW/FF

Ti0 ₂ 1.089/0.290 1.181/0.270 3.043/0.225 1.965/0.215

ZnO 0.403/0.259 0.184/0.253 0.386/0.233 0.199/0.210

A1 ₂ 0 ₃ 0.862/0.166 0658/0.181 0.576/0.217 0.770/0.239

1 h after packing 48 h after packing 1 h after packing 48 h after packing

(40 °C) (40 °C) (40 °C) (40 °C)

MxOy Pmax/MW/FF) Pmax/MW/FF Pmax/MW/FF Pmax/mW/FF

Ti0 ₂ 1.181/0.270 0.228/0.303 3.639/0.261 3.376/0.258

ZnO 0.492/0.266 0.272/0.260 0.584/0.227 0.366/0.195

A1 ₂ 0 ₃ 1.226/0.286 1.049/0.203 0.848/0.233 1.226/0.286

DETAILED DESCRIPTION OF THE INVENTION

The donor as used herein refers to tertiary amines, amides and sulfoxides. Tertiary amines being selected from triphenylamine (TPA), tetramehtyl p-phenylenediamine (TMPDA), l,4-diazabicyclo[2.2.2]octane (DABCO), N,N-diisopropylethylamine (DIPEA), preferably N,N-diisopropylethylamine (DIPEA).

The acceptors as used herein refers to /t-chloranil, p-benzoquinone, diamide and sulfone derivatives. Diamide as used in refers to phthalimide derivatives; sulfone derivatives are selected from dimethylsulfone, sulfolane.

SS material as used herein may be in the form of foil, sheet, mesh.

Aluminium material as used herein may be in the form of foil, sheets, mesh.

Metal oxide layers as used herein include Ti0 ₂ , Al ₂ 0 _3, Zn0, Ce0 ₂ , NiO, Mn0 ₂ etc. The metal oxide as such shall also act as a donor.

The metal oxide layer may optionally contain a binder made up of polymeric material such as polyacrylate, polyethylene oxide, polyvinyl Alcohol. Polyacrylates such as polymethyl methacrylate (PMMA). Appropriate solvents have to be used to cast the layers. The solvents are selected from dichloromethane, propylene carbonate (PC), N-methyl pyrrolidone, DMSO or mixtures thereof.

Sulfone derivatives used in the acceptor layer may also function as solvent.

In still another embodiment the present invention specifically provides a device the construct of which is based on layering technology as given below:

a. layer containing graphite sheet,

b. acceptor layer,

c. donor layer,

d. optionally another acceptor layer, and

e. layer containing Aluminium material.

In still another embodiment the present invention specifically provides a device the construct of which is based on layering technology as given below:

a. layer containing graphite sheet,

b. acceptor layer C1 ₄ BQ/Ti0 ₂ /PE0//Ti0 ₂ /PE0/Al ,

c. donor layer comprising of Cl ₄ BQ/donor/PC/PEO,

d. optionally another acceptor layer C1 ₄ BQ/Ti0 ₂ /PE0//Ti0 ₂ /PE0/Al, and e. layer containing Aluminium material.

When another acceptor like -benzoquinone (BQ) was used in each C1 ₄ BQ layer or was coated along with one C1 ₄ BQ layer and in another BQ layer on Ti0 ₂ /PE0/Al (Figures 4) further improvement in power output was realized.

The device of the present invention is also workable in the absence or presence of amine; absence or presence of a donor. Initially, the inventors of the present invention used Ti0 ₂ as solid support for construction of the cell device as it is widely used in the construction of solar cell and other electronic devices. The inventors of the present invention have also selected the polar propylene carbonate (PC) solvent.

The inventors of the present invention found that the polar solvent PC shall solvate electrons and functions as an electron carrier to transporting electron to the aluminum electrode. Similar results were obtained when the solvents DMSO, NMP and sulfolane were used alone or along with the PC solvent.

As per the results of the present invention, it is found that the cells can be easily constructed by making donor and acceptor pastes using Ti0 ₂ , polyethylene oxide (PEO) and PC and coating on A1 foil (0.2mm x 5cm x 5cm) and SS foil (SS 304, 0.05mm x 5cm x 5cm) or graphite sheet (0.4mm x 5cm x 5cm) electrodes (SI). Initially, the inventors of the present invention constructed a simple two layer cell using A1 (5 cm x 5 cm) and SS (SS 304, 5 cm x 5 cm) foils. The mixture Ti0 ₂ (rutile), />-chloranil, PC, EC and polyethylene oxide (PEO) was coated on A1 foil and the mixture of Ti0 ₂ (rutile), amines, PC, EC and PEO was coated on SS foil. The foils were then sandwiched to construct the electrochemical cell (Figure 2). The charge transport in this two layer electrochemical cell is expected to have contributions from both ionic conductivity and also through exchange reactions involving D/D ⁺ and A7A.

The Ti0 ₂ is also widely used as buffer layer between electrodes in solar cells. The important observation was improvement in results when the Ti0 ₂ was coated on the graphite sheet and A1 foil electrodes in the configurations shown in Figure 2. The IV curves at 28 °C, 35 °C and 40 °C and Pmax and FF (fill factor) data are listed in Figure 2. The IV-data were recorded after lh and 48 h after packing. The higher power outputs (Pmax) were observed after lhr after packing compared to that observed after 48h. Presumably, the power output becomes less as the initially formed radical cation and anion pairs would be converted to the corresponding charge transfer complex. The cells were also constructed by a similar configuration but with additional Ti0 ₂ in PC layer (Figure 3b). The cell constructed in this way produced higher power but the power output still decreased with time and there was almost no power produced after a week. Possibly, the chloranil radical anion may get deposited at the A1 electrode and the />-chloranil may not fully dissolve back in the PC solvent (only 0.03 g p- chloranil soluble in 1 mL PC), thus preventing the reversible formation of amine or amide radical cation and p- chloranil radical anion.

The inventors of the present invention have carried out experiments using p- benzoquinone (BQ) which has lower electron affinity (EA 1.91) compared to p- chloranil which has a very high electron affinity (EA) of 2.78eV to examine whether the chloranil anion radical can transfer electron to BQ to form the corresponding radical anion for further electron transport to the A1 electrode.

The inventors of the present invention have carried experiments by constructing the cell in two different configurations using p-benzoquinone in 4 layers, (Figure 4a, 4c). The cells as in configuration with additional Ti0 ₂ in the middle layers gave better results (Figure 4c) and the cell using DIPEA as donor gave maximum power (Figure 4c, Pmax values obtained at 40 °C for DIPEA, 11.74 mW at 1 h and 8.338 mW at 48 h).

The inventors of the present invention identified that the donor used in the cells could produce power without using p- chloranil as the Ti0 ₂ surface itself could accept electrons from the donors. Indeed, this was observed and DABCO gave higher power upon interaction with Ti0 ₂ (Figure 5). The inventors of the present invention have also constructed the cells using the metal oxides such as Ti0 ₂ , A1 ₂ 0 ₃ and ZnO in the configurations shown in Figure 6a and 6c without using donor amines or amide. Interestingly, the inventors of the present invention identified that the cells constructed in this way did produce power with Ti0 ₂ giving higher power when it is also present in the middle PC layers (Figure 6c). Clearly, there is electron transfer from Ti0 ₂ to />-chloranil acceptor.

The inventors of the present invention have found that the performance of the cells did improve giving same power output for a week when the cells were used for charging rechargeable Ni-Cd battery (Figure 4c, DIPEA as donor: at 40 °C, Pmax, after 1 h, 13.21 mW/FF 0.172, after 48 h, 12.77mW/FF 0.270 and after 144 h, 10.65 mW/FF 0.277). This can be attributed to the avoidance of side reactions if any, by converting the radical ions to neutral donor and acceptor by using the cells to charge a rechargeable battery.

The inventors of the present invention found that periodic addition of small amounts of the electron scavenger such as CH ₂ C1 ₂ helps in delivering higher power for longer time.

The inventors of the present invention found that when the cells (Pmax 15mW at 28 °C) kept inside a closed insulated container (1.2L) while using the cells for charging a Ni-Cd battery the temperature of the air inside the insulated box dropped from 30.2 °C to 28 °C in lh. This temperature drop is significant considering that the cooled air molecules are expected to be also heated by collision with wall of the container and also the rate of electricity harvesting would be lower when the temperature of the air molecules drops. Clearly, the cells convert the heat energy of surrounding molecules in the air to electricity leading to lowering of the air temperature and hence the cells have potential for the development of devices useful for air cooling applications. In recent years, there have been several reports on the conversion of low-grade waste heat (<130°C) to electricity by thermally regenerative electrochemical cycles. A thermoelectrochemical device based on ferrocene-iodine redox couple was also reported but this device produced only pW/m with respect to the electrode surface area. The cell constructed following the simple method described here following simple techniques based on organic electron transfer reactions at 40 °C produced power upto Pmax of 4.180mW/25cm ² (0.1672mW/cm ² or 1.672W/m ² ) (Figure 4) and the cells can easily stacked produced more power. Also, in the present case, the device utilizes very inexpensive materials that are already manufactured in large scale. Further, since there are established methods are available for heating air at even below 0 °C to 40 °C using solar radiation and methods are available for storing solar heat in simple chemicals like aq. NaOH and CaCl ₂ and for using these stored materials for heating the air to 40 °C to 60 °C, the cell device reported here has the potential for developing devices that could produce electricity 24x7, day and night, rainy or cloudy atmospheric conditions. However, long term performance of this cell device remains to be established and there is plenty of scope for further research and development to improve the performance of this device.

The inventors of the present invention have observed that the use of N- methylpyrrolidone as solvent in place of PC gave Pmax values in the range of 6-8 mW/25cm and use of the solvent sulfolane gave results comparable to PC. Also, the use of DMSO as donor in place of amines in PC and in NMP gave Pmax values in the range of 7-8 mW/25cm . Under these conditions, the power outputs of the cells were in the same range for more than a month. Clearly, the inventors of the present invention have invented a simple method for construction of ambient heat harvesting organic electrochemical cell which a trained individual can be easily modify, improve and scale up for construction of various devices for 24x7 electricity production for Household, Grid, Automobile and Air Cooling applications. EXPERIMENTAL DETAILS:

General Information: P-Chloranil, N, N-diisopropylethylamine (DIPEA), 1,4- diazabicyclo[2.2.2]octane (DABCO) and Ti0 ₂ were purchased from Avra chemicals (India). P-benzoquinone (BQ), triphenylamine (TPA), N,N’-tetramethyl-l,4- phenylenediamine (TMPD), propylene carbonate (PC), ethylene carbonate (EC) and polyethylene oxide (PEO) were purchased from Sigma Aldrich. Neutral alumina (A1 ₂ 0 ) was purchased from SRL chemicals, India. Dimethyl sulfoxide (DMSO) and Zinc oxide (ZnO) were purchased from E-Merck, India. The metal oxides were heated at 150 °C in a vacuum oven for 2 h before use. PC, EC and DMSO were always kept under molecular sieves. Graphite sheet (0.4mm thickness, 5cm x 5cm, Resistivity, p = 2xl0 ⁴ O.m) was purchased from Falcon Graphite Industries, Hyderabad, India. Aluminium Foil (0.2mm thickness, 5cm x 5cm, Resistivity, p = 2xl0 ⁵ O.m) and Stainless steel (0.4mm thickness, 5cm x 5cm, Resistivity, p = 5xl0 ⁴ O.m) were purchased from Aluminium Enterprises and Rasik Metals, Hyderabad, India. EPR spectra was recorded on a Bruker-ER073 instrument equipped with an EMX micro X source for X band measurement using Xenon 1.1b.60 software provided by the manufacturer. Electrical measurements were carried out by ZAHNER instrument using CIMPS software. The current-voltage curve was drawn using Origin software.

Preparation of Electrochemical Cells:

Simple solution processing and casting techniques were followed for the construction of the device.

Configuration 1:

The PEO (0.2 g) was dissolved in dichloromethane and mixed with Ti0 ₂ (1 g) powder. DCM was removed to obtain a paste. The p-chloranil (0.5 g), PC (0.5 g) and EC (0.5 g) were added to the above made paste and it was cast over the A1 (0.2mm thickness, 5x5 cm ). The layer was dried in air at room temperature overnight. Similarly, PEO (0.2 g), Ti0 ₂ (1 g) powder, donor amine (2 mmol), PC (0.5 g) and EC (0.5 g) were mixed and cast above SS (0.05 mm thickness, 5x5 cm ) or Graphite (0.4 mm thickness, 5x5 cm ). The layer was dried in air at room temperature overnight. The cell was prepared by sandwiching the coated Al/SS or Al/Gr layers. The rim of the cell prepared in this way was sealed all around using Ti0 ₂ /PEO paste, then with commercial synthetic rubber adhesive Bondfix (India) and covered with cellophane tape.

Configuration 2:

The PEO (0.05 g) was dissolved in dichloromethane and mixed with Ti0 ₂ (0.5 g) powder. DCM was removed to obtain a paste for coating on A1 or Graphite foils. After 1 h, CI4BQ (0.1 g)/PEO (0.05 g) in DCM was coated on Ti0 ₂ /PEO/Al and Ti0 ₂ /PEO/Gr and dried. The C1 ₄ BQ (0.025 g)/donor (O.lg) /PC (0.5 g)/PEO (0.05 g) slurry was prepared and casted above the coated layer on A1 and Graphite and dried in air at room temperature overnight. The cell was prepared by sandwiching the coated Al/Gr layers. The rim of the cell prepared in this way was sealed all around using Ti0 ₂ /PEO paste, then with commercial synthetic rubber adhesive Bondfix (India) and covered with cellophane tape.

Configuration 3:

The PEO (0.05 g)was dissolved in dichloromethane and mixed with Ti0 ₂ (0.5 g) powder. DCM was removed to obtain a paste for coating on A1 or Graphite foils. After 1 h, CI4BQ (0.1 g)/PEO (0.05 g) in DCM was coated on Ti0 ₂ /PEO/Al and Ti0 ₂ /PEO/Gr and dried. The C1 ₄ BQ (0.025 g)/donor (1 mmol)/PC (0.5 g)/Ti0 ₂ (0.25 g)/PEO (0.05 g) slurry was prepared and casted above the coated layer on A1 and Graphite and dried in air at room temperature overnight. The cell was prepared by sandwiching the coated Al/Gr layers. The rim of the cell prepared in this way was sealed all around using Ti0 ₂ /PE0 paste, then with commercial adhesive Bondfix (India) and covered with cellophane tape.

The cells described in Figures 4-6 were also constructed following the procedures similar to that described above.