Coated electrodes for liquid thermoelectric conversion devices to enhance Fe2+/Fe3+ redox kinetics

Abstract

A liquid thermoelectric conversion device (LTE) converts temperature difference between the electrodes into electric energy via electrochemical Seebeck coefficient α. Here, we systematically investigated Fe²⁺/Fe³⁺ redox kinetics at graphite-dispersion coated electrodes in 0.8 M Fe(ClO₄)₂/Fe(ClO₄)₃ aqueous solution. We found that the reciprocal of charge transfer resistance R_ct and diffusion resistance R_dif increases with increase in the electrode thickness t. In the region of t ≥ 40 μm, total resistance R becomes smaller than that of a commercially available graphite sheet (GS; t = 220 μm). The maximum output power W_max of a LTE composed of 0.8 M Fe(ClO₄)₂/Fe(ClO₄)₃ aqueous electrolyte increased by 37.5% at t = 131 μm, 24.6% at 110 μm, and 8.9% at 40 μm, as compared with that of a LTE composed of the GS.