An electrochemical oscillator for harvesting near room temperature waste heat

Abstract

We present Soret effect-driven electrochemical devices that generate >1 V with a mere 10 K temperature difference with the cold end at room temperature, i.e., a thermopower α > 100 mV K⁻¹ – almost four to five times the record to date [Adv. Energy Mater., 2019, 9, 1901085]. We show that α depends not only on the electrolyte composition but also on the electrode porosity and microstructure, which has remained an understudied area of research. Interestingly, our devices show novel voltage oscillations (unlike electrochemical oscillations observed previously, which were a result of either (a) stochastic single-molecule electrochemistry or (b) redox reactions) arising from an interplay between ionic diffusion and ionic migration within the electric double-layer, highlighting the potential for novel applications. Notably, the real-world use of TRECO is demonstrated by (a) facile continuous operation, (b) harvesting body heat (∼825 mV obtained for a temperature difference of 6 K), and (c) powering a pocket calculator using a single large format TRECO cell to harvest waste heat from warm continuously operating lab equipment.