Effect of Catalytic and Electrochemical Acetone Hydrogenation on the I–V Characteristics of an Acetone/Hydrogen-Based Thermally Regenerative Fuel Cell

A thermally regenerative fuel cell, converting low-quality heat at around 100 °C directly into electric power, is composed of a redox reaction pair of acetone hydrogenation and 2-propanol dehydrogenation. The magnitude of its open-circuit voltage (VOC) was determined by the Gibbs energy change of acetone hydrogenation, without exhibiting activation polarization. Its short-circuit current (ISC) was insensitive to the extents of catalyst loading at the anode, in contrast to the cathode, because acetone hydrogenation proceeded more slowly than hydrogen dissociation. The ISC characteristics were improved with increasing sulfuric acid concentrations at the cathode, which would have resulted from the rate enhancement of acetone reduction due to more abundant protons usable at the catalyst sites. Both VOC and ISC of the fuel cell were increased along with increasing the acetone/2-propanol ratio in the catholyte, suggesting favorable effects of the thermodynamical acetone activity and the coverage increment of acetone at the same cathode catalyst sites.