Fundamental insight into enhanced activity of Pd/CeO thin films in hydrogen oxidation reaction in alkaline media

Palladium supported on ceria (Pd/CeO 2 ) has recently raised strong interest as an alternative catalyst to platinum on the anode electrode in anion exchange membrane fuel cells. Herein, we provide new insight into the enhanced activity of Pd/CeO 2 in hydrogen oxidation reaction (HOR) in alkaline media. Using well-defined model thin films, we show that Pd/CeO 2 thin films lead to enhanced activity in HOR compared to pure Pd thin films. In situ characterization using electrochemical quartz crystal microbalance provide in-depth understanding of the role of CeO 2 . CeO 2 leads to fundamental differences in adsorption and absorption of key reaction intermediates during HOR. In combination with characterization and theoretical calculations, Pd atoms embedded in CeO 2 are shown to be present on the prepared thin films and active for hydrogen activation but are not able to bind CO during CO-stripping characterization. Finally, an estimation of the source of hydroxyl intermediates provided by CeO 2 - which could be directly participating in the reaction - is presented herein. Fundamental understanding of the Pd-CeO 2 interface in HOR opens new ways to reduce the amount of noble metals in alkaline fuel cells. In situ electrochemical quartz crystal microbalance (E-QCM) provides new insight into enhanced activity of palladium supported on ceria (Pd/CeO 2 ) in hydrogen oxidation reaction.