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Nat Commun. 2019 Sep 12;10(1):4151. doi: 10.1038/s41467-019-12144-2.

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

Author information

1
Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
2
Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, 10027, USA.
3
Department of Chemical Engineering, Ming Chi University of Technology, New Taipei City, 24301, Taiwan.
4
Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China. hpfeng@hku.hk.
5
The University of Hong Kong-Zhejiang Institute of Research and Innovation (HKU-ZIRI), Hangzhou, 311300, Zhejiang, China. hpfeng@hku.hk.

Abstract

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 Fe2+/Fe3+ 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 Fe2+/Fe3+, and then discharges continuously by oxidizing polyaniline and reducing Fe3+ under isothermal heating till Fe3+ 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.

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