Precipitation enhancement of liquid thermoelectric conversion with Fe(ClO4)2/Fe(ClO4)3 dissolved in DMF

Abstract

The electrochemical Seebeck coefficient α is one of the parameters that determines the performance of liquid thermoelectric conversion devices (LTEs). We systematically investigated α in N,N-dimethylformamide (DMF) containing both m M Fe(ClO₄)₂ and m M Fe(ClO₄)₃ against m. Above 0.35 M, we observed significant enhancement of α due to precipitates containing Fe³⁺. In addition, the precipitation enhances the maximum power of the LTE at 0.4 M by as much as 32%. The precipitation enhancement of α cannot be explained only by the concentration gradient model. We propose a solution-solid equilibrium of Fe³⁺ as an additional precipitate effect, which can fill the difference between the concentration gradient model and observed α.