Ethanol Electrolysis at Carbon-Supported PtRh Alloy Nanoparticles in a Proton Exchange Membrane Cell

Electrochemical oxidation of ethanol in proton exchange membrane (PEM) cells can provide sustainable energy technology through the production of hydrogen by ethanol electrolysis at lower cell potentials relative to water electrolysis. However, there are no catalysts available for the complete oxidation of ethanol to carbon dioxide, which is required for 100% hydrogen production selectivity. The addition of Rh to Pt-based catalysts promotes the complete oxidation of ethanol, although the role of Rh is unclear. Here, PtRh alloy catalysts are shown to provide higher activities than Pt and higher selectivity for the complete oxidation of ethanol in a PEM electrolysis cell at 80 °C. A Pt3.0Rh catalyst provided a faradaic yield of 79% for CO2 formation, while yields at Pt and Rh catalysts were 66% and 52%, respectively. Cyclic voltammetry revealed that the increased performances of the PtRh catalysts were due predominantly to the effect of lattice compression (strain) on the active Pt sites. Increasing the Pt content of the alloy increased the peak current for ethanol oxidation by increasing the fraction of surface Pt sites and enhanced CO2 production, while the decreasing strain increased half-wave and peak potentials.