Direct thermal charging cell for converting low-grade heat to electricity

• Published in: Nature communications Vol. 10; no. 1; pp. 4151 - 8
• Main Authors: Wang, Xun, Huang, Yu-Ting, Liu, Chang, Mu, Kaiyu, Li, Ka Ho, Wang, Sijia, Yang, Yuan, Wang, Lei, Su, Chia-Hung, Feng, Shien-Ping
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.09.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 140/133; 140/146; 147/135; 639/4077/4072/4062; 639/4077/4107; Charging; Conversion; Depletion; Efficiency; Electricity; Electrolytic cells; Emissions control; Graphene; Greenhouse effect; Greenhouse gases; Heat; Heat recovery; Heating; Humanities and Social Sciences; Iron; multidisciplinary; Nanoparticles; Oxidation; Platinum; Polyanilines; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-12144-2

Efficient low-grade heat recovery can help to reduce greenhouse gas emission as over 70% of primary energy input is wasted as heat, but current technologies to fulfill the heat-to-electricity conversion are still far from optimum. Here we report a direct thermal charging cell, using asymmetric electrodes of a graphene oxide/platinum nanoparticles cathode and a polyaniline anode in Fe 2+ /Fe 3+ redox electrolyte via isothermal heating operation. When heated, the cell generates voltage via a temperature-induced pseudocapacitive effect of graphene oxide and a thermogalvanic effect of Fe 2+ /Fe 3+ , and then discharges continuously by oxidizing polyaniline and reducing Fe 3+ under isothermal heating till Fe 3+ depletion. The cell can be self-regenerated when cooled down. Direct thermal charging cells attain a temperature coefficient of 5.0 mV K −1 and heat-to-electricity conversion efficiency of 2.8% at 70 °C (21.4% of Carnot efficiency) and 3.52% at 90 °C (19.7% of Carnot efficiency), outperforming other thermoelectrochemical and thermoelectric systems. Recovery of low-grade heat can aid in reducing greenhouse gas emissions, but heat-to-electricity conversion technologies should be optimized. Here the authors report a direct thermal charging cell that uses asymmetric electrodes and a redox electrolyte to efficiently convert low-grade heat into electricity.