Effect of electrolytes on performance of CuHCF electrode of thermally regenerative electrochemical cycle system for harvesting low-grade heat

Abstract

A huge amount of low-grade heat exists in nature and industrial sectors, but is difficult to harvest. Recycling low-grade heat is of great significance for saving energy and reducing pollutant emissions. The thermally regenerative electrochemical cycle (TREC) system has attracted much attention because of its high conversion efficiency for low-grade thermal energy. The electrolyte has an important influence on the performance of the electrochemical system, but few researches have been done in the field of TREC. Here, the influences of the electrolyte, that is, the cation, electrolyte concentration and anion, on the performance of the CuHCF electrode are studied. Experiments have proved that the K+ and NH4+ cation systems have superior heat-to-electricity conversion performance. In addition, appropriately reducing the electrolyte concentration is beneficial to increase the net work output. As the electrolyte concentration is reduced from 3 M to 1 M, the CuHCF electrode obtains a larger temperature coefficient (−0.629 mV K−1) and net output power (0.96 mWh g−1). Among the different anion systems, the NO3– system has more superior heat-to-electricity conversion performance, with a net output work of 1.06 mWh g−1. This research is instructive for the performance improvement of TREC system through electrolyte optimization.