Redox Targeting-Based Thermally Regenerative Electrochemical Cycle Flow Cell for Enhanced Low-Grade Heat Harnessing.

Zhang, Hang; Zhang, Feifei; Yu, Juezhi; Zhou, Mingyue; Luo, Wei; Lee, Yann Mei; Si, Mayan; Wang, Qing · Adv Mater · 2021

basic_science · Level V

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Abstract

A large amount of low-grade heat (<100 °C) is produced in electrical devices and mostly wasted. This type of heat without effective dissipation also causes compromised device performance, reliability, and lifespan. To tackle these issues, a redox targeting (RT)-based flow cell with judiciously designed thermoelectrically active redox materials is demonstrated for the first time for efficient heat-to-electricity conversion through a thermally regenerative electrochemical cycle (TREC). Compared with the conventional TREC systems, the RT-based flow cell not only reveals considerably enhanced thermoelectric efficiency, but the flow of redox fluids also provides a cooling function to the system. In this work, solid material Ni<sub>0.2</sub> Co<sub>0.8</sub> (OH)<sub>2</sub> and redox mediator [Fe(CN)<sub>6</sub> ]<sup>4-/3-</sup> , both of which have negative temperature coefficient and share identical redox potential, are paired via RT-reactions to boost the capacity and meanwhile thermoelectric efficiency of a [Fe(CN)<sub>6</sub> ]<sup>4-/3-</sup> /Zn<sup>0/2+</sup> -based flow cell. Upon operating over the TREC cycle, the RT-based flow cell converts heat to electricity at an unprecedented absolute thermoelectric efficiency of 3.61% in the temperature range of 25-55 °C.