Recent developments in Pd-CeO2 nano-composite electrocatalysts for anodic reactions in anion exchange membrane fuel cells

In 2016, for the first time a polymer electrolyte fuel cell free of Pt electrocatalysts was shown to deliver more than 0.5 W cm-2 of peak power density from H2 and air (CO2 free). This was achieved with a silver-based oxygen reduction (ORR) cathode and a Pd-CeO2 hydrogen oxidation reaction (HOR) anodic electrocatalyst. The poor kinetics of the HOR under alkaline conditions is a considerable challenge to Anion Exchange Membrane Fuel Cell (AEMFC) development as high Pt loadings are still required to achieve reasonable performance. Previously, the ameliorative combination of Pd and CeO2 nanocomposites has been exploited mostly in heterogeneous catalysis where the positive interaction is well documented. Carbon supported Pd-CeO2 HOR catalysts have now been prepared by different synthetic techniques and employed in AEMFCs as alternative to Pt and PtRu standards. Important research has also been recently reported, delving into the origin of the HOR enhancement on Pd-CeO2. Such work has highlighted the importance of the bifunctional mechanism of the HOR at high pHs. Carefully prepared nano-structures of Pd and CeO2 that promote the formation of the Pd-O-Ce interface provide optimal binding of both Had and OHad species, aspects which are crucial for enhanced HOR kinetics. This review paper discusses the recent advances in Pd-CeO2 electrocatalysts for AEMFC anodes.