Rational design of carbon electrodes of thermoelectrochemical cells for efficient low-grade heat harvesting

Thermoelectrochemical cells (TECs) are promising and cost-effective for harvesting low-grade heat. However, the low efficiency hinders their practical application. Here, a multi-level three-dimensional carbon electrode was designed for high-efficiency TECs. The composite electrode is prepared by loading nitrogen-doped carbon nanowires on carbon cloth fibers (N–CNW@CC); it improves the transition kinetics of Fe(CN)63−/Fe(CN)64− and accelerates the ion transmission simultaneously. As a result, the output current of the N–CNW@CC based TEC is 26.3% higher than that of the initial CC. Upon combining it with an optimized thermosensitive crystallization-boosting electrolyte, the Carnot-relative efficiency of the N–CNW@CC based TEC reaches up to 13.02%, which is the highest efficiency ever reported. In addition, a simple pack of a series of TECs can drive a commercial timer to work for an hour continuously. This N–CNW@CC electrode holds great potential to realize the commercial application of TECs.