Hybrid thermo-electrochemical energy harvesters for conversion of low-grade thermal energy into electricity via tungsten electrodes

Abstract

Thermo-electrochemical cells utilizing aqueous hexacyanoferrate electrolytes are recognized as an effective energy harvesting system for low-grade waste heat (≤170 °C) owing to their high stability and simple design. Nevertheless, the power generation of thermo-electrochemical cells is low due to the Seebeck coefficient of hexacyanoferrate electrolyte. Herein, we propose hybrid thermo-electrochemical cells using tungsten electrodes, exploiting the redox reaction of hexacyanoferrate and oxidation of the tungsten electrode. Enhanced Seebeck coefficient was attributed to the combination of the two reactions: the redox reaction of the electrolyte and oxidation reaction of tungsten electrodes. The developed tungsten electrode-based hybrid thermo-electrochemical cells generated a Seebeck coefficient of 1.66 mV K−1 and 425 mW m−2 at a dT of 50 °C, ~ 70% higher the power output of platinum and carbon electrodes. From an economic viewpoint, the cost of tungsten makes up for its inevitable consumption due to dissolution and the cost of periodic electrode replacement. Our system is an innovative solution, which might contribute to the commercialization of thermo-electrochemical cells.