The authors acknowledge constructive discussion with Prof. D.Y.C. Leung and Dr. Y. Chen (The University of Hong Kong), Prof. M.H.K. Leung (City University of Hong Kong), Dr. W. S. Liu (Southern University of Science and Technology), and Mr. Frank H.T. Leung (Techskill [Asia] Limited). The authors acknowledge the financial support of General Research Fund of the Research Grants Council of Hong Kong Special Administrative Region, China, under Award Number 17204516 and 17206518, and Innovation and Technology Fund (Ref: ITS/171/16FX).

1. Preparation of the graphene oxide electrode
<ol>
	<li>Synthesis of graphene oxide via the modified Hummer&#39;s method
	<ol>
		<li>Steps 1.1.2 and 1.1.3 occur at a low temperature (&#60;0 &#176;C). Circulate ice water flowing through the external layer of a double wall glass beaker placed on a magnetic stirrer to create low temperature conditions for the reactants inside.</li>
		<li>Mix 1 g of sodium nitrate (NaNO3) with 100 mL of sulfuric acid (H2SO4, reagent grade, 95-98%) using sl...

<ol>
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K., Pardemann, R., Meyer, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimating+the+Global+Waste+Heat+Potential.">Estimating the Global Waste Heat Potential.</a> Renewable and Sustainable Energy Reviews. 57, 1568-1579 (2016).</li><li>Gur, I., Sawyer, K., Prasher, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Searching+for+A+Better+Thermal+Battery.">Searching for A Better Thermal Battery.</a> Science. 335 (6075), 1454-1455 (2012).</li><li>He, R., Schierning, G., Nielsch, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoelectric+Devices:+A+Review+of+Devices,+Architectures,+and+Contact+Optimization.">Thermoelectric Devices: A Review of Devices, Architectures, and Contact Optimization.</a> Advanced Materials Technologies. 3 (4), 1700256 (2018).</li><li>Abraham, T. J., MacFarlane, D. R., Pringle, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+Seebeck+Coefficient+Redox+Ionic+Liquid+Electrolytes+for+Thermal+Energy+Harvesting.">High Seebeck Coefficient Redox Ionic Liquid Electrolytes for Thermal Energy Harvesting.</a> Energy &amp; Environmental Science. 6 (9), 2639-2645 (2013).</li><li>Zhang, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+Power+Density+Electrochemical+Thermocells+for+Inexpensively+Harvesting+Low-Grade+Thermal+Energy.">High Power Density Electrochemical Thermocells for Inexpensively Harvesting Low-Grade Thermal Energy.</a> Advanced Materials. 29 (12), 1605652 (2017).</li><li>Duan, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aqueous+Thermogalvanic+Cells+with+A+High+Seebeck+Coefficient+for+Low-Grade+Heat+Harvest.">Aqueous Thermogalvanic Cells with A High Seebeck Coefficient for Low-Grade Heat Harvest.</a> Nature Communications. 9 (1), 5146 (2018).</li><li>Im, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-Efficiency+Electrochemical+Thermal+Energy+Harvester+Using+Carbon+Nanotube+Aerogel+Sheet+Electrodes.">High-Efficiency Electrochemical Thermal Energy Harvester Using Carbon Nanotube Aerogel Sheet Electrodes.</a> Nature Communications. 7, 10600 (2016).</li><li>Hu, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Harvesting+Waste+Thermal+Energy+Using+A+Carbon-Nanotube-Based+Thermo-Electrochemical+Cell.">Harvesting Waste Thermal Energy Using A Carbon-Nanotube-Based Thermo-Electrochemical Cell.</a> Nano Letters. 10 (3), 838-846 (2010).</li><li>Poletayev, A. D., McKay, I. S., Chueh, W. C., Majumdar, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Continuous+Electrochemical+Heat+Engines.">Continuous Electrochemical Heat Engines.</a> Energy and Environmental Science. 11 (10), 2964-2971 (2018).</li><li>Qian, W., Li, M., Chen, L., Zhang, J., Dong, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improving+Thermo-Electrochemical+Cell+Performance+by+Constructing+Ag-MgO-CNTs+Nanocomposite+Electrodes.">Improving Thermo-Electrochemical Cell Performance by Constructing Ag-MgO-CNTs Nanocomposite Electrodes.</a> RSC Advances. 5 (119), 97982-97987 (2015).</li><li>Lee, S. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+Electrochemical+System+for+Efficiently+Harvesting+Low-Grade+Heat+Energy.">An Electrochemical System for Efficiently Harvesting Low-Grade Heat Energy.</a> Nature Communications. 5, 3942 (2014).</li><li>Yang, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Charging-Free+Electrochemical+System+for+Harvesting+Low-Grade+Thermal+Energy.">Charging-Free Electrochemical System for Harvesting Low-Grade Thermal Energy.</a> Proceedings of the National Academy of Sciences. 111 (48), 17011-17016 (2014).</li><li>Yang, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Membrane-Free+Battery+for+Harvesting+Low-Grade+Thermal+Energy.">Membrane-Free Battery for Harvesting Low-Grade Thermal Energy.</a> Nano Letters. 14 (11), 6578-6583 (2014).</li><li>Fukuzumi, Y., Amaha, K., Kobayashi, W., Niwa, H., Mortitomo, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prussian+Blue+Analogues+as+Promising+Thermal+Power+Generation+Materials.">Prussian Blue Analogues as Promising Thermal Power Generation Materials.</a> Energy Technology. 6 (10), 1865-1870 (2018).</li><li>Shibata, T., Fukuzumi, Y., Kobayashi, W., Moritomo, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+Power+Generation+During+Heat+Cycle+Near+Room+Temperature.">Thermal Power Generation During Heat Cycle Near Room Temperature.</a> Applied Physics Express. 11 (1), 017101 (2018).</li><li>Shibata, T., Fukuzumi, Y., Moritomo, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+Efficiency+of+A+Thermocell+Made+of+Prussian+Blue+Analogues.">Thermal Efficiency of A Thermocell Made of Prussian Blue Analogues.</a> Scientific Reports. 8 (1), 14784 (2018).</li><li>Takahara, I., Shibata, T., Fukuzumi, Y., Moritomo, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+Thermal+Cyclability+of+Tertiary+Battery+Made+of+Prussian+Blue+Analogues.">Improved Thermal Cyclability of Tertiary Battery Made of Prussian Blue Analogues.</a> ChemistrySelect. 4 (29), 8558-8563 (2019).</li><li>Zhang, F., Liu, J., Yang, W., Logan, B. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Thermally+Regenerative+Ammonia-Based+Battery+for+Efficient+Harvesting+of+Low-Grade+Thermal+Energy+as+Electrical+Power.">A Thermally Regenerative Ammonia-Based Battery for Efficient Harvesting of Low-Grade Thermal Energy as Electrical Power.</a> Energy and Environmental Science. 8 (1), 343-349 (2015).</li><li>Zhu, X., Rahimi, M., Gorski, C. A., Logan, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Thermally-Regenerative+Ammonia-Based+Flow+Battery+for+Electrical+Energy+Recovery+from+Waste+Heat.">A Thermally-Regenerative Ammonia-Based Flow Battery for Electrical Energy Recovery from Waste Heat.</a> ChemSusChem. 9 (8), 873-879 (2016).</li><li>Zhang, F., LaBarge, N., Yang, W., Liu, J., Logan, B. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancing+Low-Grade+Thermal+Energy+Recovery+in+a+Thermally+Regenerative+Ammonia+Battery+Using+Elevated+Temperatures.">Enhancing Low-Grade Thermal Energy Recovery in a Thermally Regenerative Ammonia Battery Using Elevated Temperatures.</a> ChemSusChem. 8 (6), 1043-1048 (2015).</li></ol>

The aTEC converts thermal energy into electricity via a thermal charging process when heating from RT to TH and a successive electrical discharging process at TH. Getting rid of the dependence on a temperature gradient or a temperature cycle like the TGC and TREC, aTEC allows isothermal heating operation during the entire charging and discharging processes. Thermal induced voltage is based on the pseudocapacitive effect of GO because heating facilitates the chemisorption of protons on the oxygen fun...

Ubiquitous low-grade heat energy (&#60;100 &#176;C) could be recycled and converted into electricity1,2 but is instead wasted. Unfortunately, heat recovery is still a great challenge, because converting low-grade heat to electricity is usually inefficient due to the low temperature differential and the distributed nature of the heat sources3. Intensive research has been conducted in solid-state thermoelectric (TE) materials and devices for the past decades, but the scalable application of TE devices in a low-grade heat regime is limited by the low energy conversion efficiency (&#951;E) of &#60;2%4.
Alternative approaches based on the effect of temperature on electrochemical cells have been suggested as a solution to this problem, because the ionic Seebeck coefficient (&#945;) of thermoelectrochemical cells (TECs) is much higher than that of TE semiconductors5,6. Thermogalvanic cells (TGC) utilize redox active electrolytes sandwiched between two identical electrodes to generate a voltage across the cell when a thermal gradient is applied. The commonly used aqueous Fe(CN)63-/Fe(CN)64- electrolyte in TGCs was reported to have an &#945; of -1.4 mV/K and yield an &#951;E of &#60;1%7,8,9,10,11. However, TGCs suffer the drawback of the poor ionic conductivity of the liquid electrolyte, which is around three orders of magnitude smaller than the electronic conductivity in TE materials. The electric conductivity could be improved, but this improvement is always accompanied by a higher thermal conductivity, which leads to a lower temperature gradient. Therefore, the &#951;E of TGCs is inherently limited due to the trade-off between the liquid electrolyte conductance and the temperature requirement for the desired redox reactions in each side of the electrode.
A thermally regenerative electrochemical cycle (TREC)12,13,14 based on a battery system using a solid copper hexacyanoferrate (CuHCF) cathode and a Cu/Cu+ anode was recently reported. TREC is configured as a pouch cell to improve the electrolyte conductance, showing an &#945; of &#8722;1.2 mV/K and reaching a high &#951;E of 3.7% (21% of &#951;carnot) when operated at 60 &#176;C and 10 &#176;C. Nevertheless, one limit of TREC is that external electricity is required at the start of the process to charge the electrodes in each thermal cycle, leading to complicated system designs14. A TREC without this limitation can be achieved, but it suffers from a poor conversion efficiency of &#60;1%13. The TREC system demonstrates that a sodium-ion secondary battery (SIB)-type thermocell consisting of two types of Prussian blue analogues (PBA) with different &#945; values can harvest waste heat. The thermal efficiency (&#951;) increases proportionally with &#916;T. Moreover, &#951; reaches 1.08%, 3.19% at &#916;T = 30 K, 56 K separately. The thermal cyclability is improved using Ni-substituted PBA15,16,17,18.
Alternatively, a thermally regenerative ammonia battery (TRAB) employs copper-based redox couples [Cu(NH3)42+/Cu and Cu(II)/Cu] that operate with the reverse temperature gradient by switching the temperature of electrolyte co-operated with positive and negative electrodes, which produces a &#951;E of 0.53% (13% of &#951;carnot). However, this system is configured with two tanks full of liquid electrolyte, causing sluggish heating and cooling. Also, the ammonia stream in the system creates concerns regarding safety, leakage, and stability19,20,21.
Here we present an asymmetric thermoelectrochemical cell (aTEC) for heat-to-electricity conversion that can be thermally charged and electrically discharged by continuous isothermal heating without maintaining a temperature gradient in a geometric configuration or switching temperatures in a thermal cycle. The aTEC uses asymmetric electrodes, including a graphene oxide (GO) cathode and a polyaniline (PANI) anode, and KCl as the electrolyte. It is thermally charged via the thermo-pseudocapacitive effect of GO and then discharged with the oxidation reaction of PANI. Notably, the aTEC exhibits a high &#945; of 4.1 mV/K and attains a &#951;E of 3.32%, the highest ever achieved at 70 &#176;C (25.3% of &#951;Carnot).

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Alumina laminated film</td>
			<td>Showa Denko</td>
			<td>SPALF C4</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbon black</td>
			<td>Alfa Aesar</td>
			<td>H30253.22</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbon paper</td>
			<td>CeTech Co. Ltd</td>
			<td>W0S1009</td>
			<td></td>
		</tr>
		<tr>
			<td>Carboxymethyl cellulose (CMC)</td>
			<td>Guidechem company</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DC Power supply</td>
			<td>B&#38;K Precision</td>
			<td>Model 913-B</td>
			<td></td>
		</tr>
		<tr>
			<td>Doctor blade coater</td>
			<td>Shining Energy Co. Ltd</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Gamry</td>
			<td>Gamry Instruments</td>
			<td>Reference 3000</td>
			<td></td>
		</tr>
		<tr>
			<td>Graphite</td>
			<td>Sigma-Aldrich</td>
			<td>332461-2.5KG</td>
			<td></td>
		</tr>
		<tr>
			<td>Mixer</td>
			<td>Thinky</td>
			<td>ARE-250</td>
			<td></td>
		</tr>
		<tr>
			<td>Nickel tab</td>
			<td>Tianjin Iversonchem company</td>
			<td></td>
			<td>4 mm width</td>
		</tr>
		<tr>
			<td>N-Methyl-2-pyrrolidone (NMP)</td>
			<td>Sigma-Aldrich</td>
			<td>443778-1L</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyaniline (leucoemeraldine base)</td>
			<td>Sigma-Aldrich</td>
			<td>530670-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>potassium permanganate (KMnO4)</td>
			<td>Sigma-Aldrich</td>
			<td>223468-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Separator</td>
			<td>CLDP</td>
			<td></td>
			<td>25 um thickness</td>
		</tr>
		<tr>
			<td>Sodium nitrate (NaNO3)</td>
			<td>Sigma-Aldrich</td>
			<td>S5506-250G</td>
			<td></td>
		</tr>
		<tr>
			<td>Styrene butadiene</td>
			<td>Tianjin Iversonchem company</td>
			<td>BM400</td>
			<td></td>
		</tr>
		<tr>
			<td>Sulfuric acid</td>
			<td>Sigma-Aldrich</td>
			<td>320501-2.5L</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermoelectric modules</td>
			<td>CUI Inc.</td>
			<td>CP455535H</td>
			<td></td>
		</tr>
		<tr>
			<td>Titanum foil</td>
			<td>Qingyuan metal</td>
			<td></td>
			<td>0.03 mm thickness</td>
		</tr>
	</tbody>
</table>

asymmetric thermoelectrochemical cell for harvesting low-grade heat under isothermal operation

Low-grade heat is abundantly available in the environment as waste heat. The efficient conversion of low-grade heat into electricity is very difficult. We developed an asymmetric thermoelectrochemical cell (aTEC) for heat-to-electricity conversion under isothermal operation in the charging and discharging processes without exploiting the thermal gradient or the thermal cycle. The aTEC is composed of a graphene oxide (GO) cathode, a polyaniline (PANI) anode, and 1M KCl as the electrolyte. The cell generates a voltage due to the pseudocapacitive reaction of GO when heating from room temperature (RT) to a high temperature (TH, ~40-90 &#176;C), and then current is successively produced by oxidizing PANI when an external electrical load is connected. The aTEC demonstrates a remarkable temperature coefficient of 4.1 mV/K and a high heat-to-electricity conversion efficiency of 3.32%, working at a TH = 70 &#176;C with a Carnot efficiency of 25.3%, unveiling a new promising thermoelectrochemical technology for low-grade heat recovery.

The aTEC pouch cell was configured with asymmetric electrodes consisting of a GO cathode, a PANI anode, and filled with the KCl electrolyte. The thickness of the pouch cell shown in Figure 1A is 1 mm, which facilitates isothermal conditions between the two electrodes as well as efficient heat conduction. The scanning electron microscopy (SEM) images of the GO cathode and the PANI anode coated on carbon paper are shown in ...

Watch this Scientific Journal Video about Asymmetric Thermoelectrochemical Cell for Harvesting Low-grade Heat under Isothermal Operation at JoVE.com

Asymmetric Thermoelectrochemical Cell for Harvesting Low-grade Heat under Isothermal Operation

Low-grade heat is abundant, but its efficient recovery is still a great challenge. We report an asymmetric thermoelectrochemical cell using graphene oxide as a cathode and polyaniline as an anode with KCl as the electrolyte. This cell works under isothermal heating, exhibiting a high heat-to-electricity conversion efficiency in low-temperature regions.

Low-grade heat is abundantly available in the environment as waste heat. The efficient conversion of low-grade heat into electricity is very difficult. We ...

Low-grade heat is abundant, but efficient low-grade heat recovery is still a great challenge. So here, we propose an asymmetric thermal cell with a high-energy efficiency over 3%The asymmetric thermal cell is thermally charged and electrically discharged under isothermal operation, so it has potential for various applications, due to its flexibility, low cost, and light weight. The performance of asymmetric thermal cell depends heavily on the content of oxygen-functional groups and the quality of electrodes.Researchers are suggested to strictly follow the protocol. Visual demonstration helps better understand the structure of asymmetric thermocell as a new technique, and ensures the production quality. Demonstrating the procedure will be Mu Kaiyu and Wang Xun, graduate student, and Dr.Huang Yu-Ting, post-doctorate from our lab.To set up a cold water bath, place a double-walled glass beaker on a magnetic stirrer, and circulate ice water through the external layer. Pour 100 milliliters of sulfuric acid into the beaker, and turn on the magnetic stirrer. Add one gram of sodium nitrate to the beaker.Add one gram of flake graphite to the beaker containing the sulfuric acid, and stir for one hour in the cold bath. After one hour, gradually add six grams of potassium permanganate to the solution. Stir the mixture for another two hours.After two hours, replace the ice water in the external layer with the water at a temperature of 35 degrees Celsius. Change the reaction environment to 35 degrees Celsius for further procedure. Continue the oxidation of the graphite by stirring for one half-hour.Add 46 milliliters of deionized water into the beaker one drop at a time, which will raise the temperature of the beaker to the range of 80 to 90 degrees Celsius. The synthesis of graphene oxide is an intense reaction. Please strictly follow the protocol, and conduct the experiments in the film hood, with proper laboratory safety equipment.Add 140 milliliters of deionized water, and then 20 milliliters of hydrogen peroxide. Look for golden particles of graphene oxide to appear as a result. Wash the product thoroughly several times with dilute hydrochloric acid and deionized water until the graphene oxide suspension reaches a pH of seven.Freeze the washed graphene oxide suspension overnight. Dry it in a freeze-dryer until the water evaporates completely. Mix graphene oxide, carbon black, and PVDF in a mass ratio of 75 to 15 to 10, and put them in a glass bottle.Measure a quantity of solvent N-Methyl-2-pyrrolidone that is four times the mass of the graphene oxide-carbon black-PVDF mixture. Drip the solvent into the solid mixture. Use a mixer to create a paste.Mix the solvent and solid at 2, 000 RPM for 30 minutes. Then, de-foam at 1, 200 RPM for two minutes. Brush-coat the paste on carbon paper until the coat has a mass loading of eight to 15 milligrams per square centimeter.Dry it for four hours at 40 degrees Celsius. To prepare a carboxymethylcellulose solution, dissolve CMC powder 1%by weight in deionized water. Stir for 10 hours.Next, add 50 milligrams of gluco-emeraldine-base polyaniline and 10 milligrams of carbon black to a beaker. Then, add 150 microliters of the carboxymethylcellulose solution to the beaker. Mix with a magnetic stirrer for 12 hours.To complete preparation of the polyaniline slurry, add six microliters of 40%styrene-butadiene solution to the beaker, and stir for another 15 minutes. Place a piece of carbon paper on the doctor blade coater. Drop the mixed polyaniline slurry at the leading edge of the carbon paper.Blade-coat the slurry to produce a film 400 micrometers thick on the carbon paper. Dry the coating for four hours at 50 degrees Celsius. Make current collectors by cutting titanium foil into the appropriate size.Use a 20 kilohertz ultrasonic spot-welding machine to connect each piece of foil to a nickel tab. Place a porous, hydrophilic, polypropylene-based separator between the graphene oxide electrode and a polyaniline electrode. Stack each electrode with one current collector.Assemble the asymmetric thermal electro-chemical cell pouch, or asymmetric thermocell, by packing the electrodes in aluminum-laminated film. Using a compact vacuum sealer, seal three sides of the aluminum-laminated film for four seconds. Inject 500 microliters of one-molar potassium chloride electrolyte into the pouch, and allow it to equilibrate for 10 minutes.Then, extrude the excess electrolyte. Seal the last side of the pouch in the vacuum sealer. Apply thermal paste to interfaces of pouch cell, to ensure good thermal contact.To set up the temperature control system, stack the asymmetric thermocell between two thermo-electric modules. Place thermal couples on the top and bottom sides of the cell. Use a potentiostat to perform electrochemical tests of the asymmetric thermocell.Conduct the thermal charging in open-circuit mode. Carry out the electrical discharging process in closed mode, at a constant current. A built-in voltage, delta-v not, was observed in open-circuit conditions at room temperature.When the asymmetric thermocell was heated from room temperature to high temperature, the cell voltage increased as electrons moved to the surface of the graphene oxide. When an external load was connected, the asymmetric thermocell was discharged. When the asymmetric thermocell was heated from room temperature to a high temperature of 70 degrees Celsius, the open circuit potential reached 0.185 volts.Discharge of the asymmetric thermocell was conducted under a constant current of 0.1 milliamps. The output electrical work was calculated by integrating the discharging voltage over the charge capacity. The asymmetrical thermocell attained an energy conversion efficiency of 3.32%equivalent to 25.3%of the Carnot efficiency.Compared to other thermoelectrochemical systems, the energy conversion efficiency of the asymmetric thermocell is the highest ever achieved at 70 degrees Celsius. The asymmetric thermocell has the potential to be used to convert waste heat to electricity in a wide variety of scenarios. The oxygen functional groups are essential to the thermal pseudo-compactive effect of graphene oxide.The quality of the synthesis of graphene oxide, and the materials loading in step 3.4, are important. The efficiency and the securability of asymmetric thermocells can be improved by changing the electrode materials. For example, by using Prussian blue analog as the anode.This technology first explored heat-to-electricity conversion under isothermal operations, and revolutionized the thermal electrochemical systems.

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6.6K visualizações.  University of Hong Kong. O calor de baixo grau é abundante, mas a recuperação eficiente de calor de baixo grau ainda é um grande desafio. Então, aqui, propomos uma célula térmica assimétrica com alta eficiência energética acima de 3%A célula térmica assimétrica é carregada termicamente e eletricamente descarregada sob operação isotérmica, por isso tem potencial para várias aplicações, devido à sua flexibilidade, baixo custo e peso leve. O desempenho das células térmicas assimétricas depende fo...