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

The electrochemical Seebeck coefficient alpha is one of the parameters that determines the performance of liquid thermoelectric conversion devices (LTEs). We systematically investigated alpha 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 alpha 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 alpha 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 alpha.