Unexpected hydrogen oxidation selectivity of Pt/NbTiO2 catalysts

Abstract

Significant advances in pushing the limits of platinum group metal (PGM) mass activities are promising to allow for ultra low PGM loaded membrane electrode assembly (MEA) designs of <0.125g/kW while still maintaining the required performance. However, due to the very low loading/thickness of these next generation catalyst layers, it is anticipated that durability will become a key challenge. Specifically, during air/air start-up shutdown (SU/SD) events, the cathode can reach very high potentials of >1.5V, leading to significant oxidation of the catalyst support. In this work, a novel solution to overcoming SU/SD losses is proposed, which relies on a previously unreported mechanism of imparting hydrogen oxidation reaction (HOR) selectivity to a relatively well known Pt/NbTiO2 catalyst. Rotating disc electrode (RDE) testing is used to study this effect and help elucidate the mechanism, while in-situ membrane electrode assembly (MEA) testing is performed to verify that the same effect can be achieved at the MEA level. This novel finding could allow for critical enabling technology for next generation durable MEA designs.