Electrochemical Oxidation of Ethanol and Methanol at Rh@Pt Catalysts at 80 °C in Proton Exchange Membrane (PEM) Cells

Abstract

Efficient oxidation of ethanol to carbon dioxide is crucial for the development of sustainable electrochemical generation of power and hydrogen from bioethanol. However, high anode overpotentials and partial oxidation to acetaldehyde and acetic acid result in low efficiencies and waste management issues. Bimetallic Rh-Pt catalysts have shown enhanced activities and CO _2 production in aqueous electrolytes, but not in proton exchange membrane (PEM) cells. In this work Rh@Pt core–shell catalysts, prepared from commercial carbon-supported Rh, have been evaluated in both aqueous H _2 SO _4 and PEM cells. Cyclic voltammetry of aqueous methanol and ethanol has shown that the catalytic activity of the Pt shell is increased by the compressive strain induced by the Rh core, and that there is also a significant bifunctional effect at low Pt coverages. In PEM cells, these effects also increase selectivity for cleavage of the C–C bond of ethanol to produce CO _2 , which will enhance the efficiencies of ethanol fuel and electrolysis cells for producing power and hydrogen, respectively. Deposition of 0.5 monolayers of Pt onto the Rh core produced the highest CO _2 yields at the lowest anode overpotentials, while higher coverages of Pt increased performances and CO _2 yields at higher potentials.

Keywords

• fuel cells - PEM
• core-shell
• rhodium
• electrolysis
• methanol