Converting Heat to Electrical Energy Using Highly Charged Polyoxometalate Electrolytes

Thermally regenerative electrochemical cycles and thermogalvanic cells harness redox entropy changes (Src) to interconvert heat and electricity, with applications in heat harvesting and energy storage. Their efficiencies depend on Src because it relates directly to the Seebeck coefficient, yet few approaches exist for controlling reaction entropy. Here, we demonstrate the use of highly charged molecular species in thermogalvanic devices. As a proof-of-concept, the highly charged Wells-Dawson ion [P2W18O62]6- exhibits large ΔSrc (-195 J mol-1 K-1) and a Seebeck coefficient comparable to state-of-the-art electrolytes (1.1 mV K-1), demonstrating the potential of linking the rich chemistry of polyoxometalates to thermogalvanic technologies.