Enhancement of the Hydrogen Oxidation Reaction in Alkaline Media via a Bi-functional Effect Using Tantalum as an Oxophilic Agent on NiMo/C

Abstract

To avoid the increase of cost owing to the use of Pt group metal (PGM) catalysts, anion-exchange membrane fuel cells (AEMFCs) operating in an alkaline electrolyte environment where non-precious metals can be used are promising. However, the performance limitations of PGM-free catalysts still need to be overcome. In this study, Ta-on-NiMo/C fabricated by adding Ta on the surface of commercial NiMo/C via physical vapor deposition was developed as an anodic catalyst for AEMFCs with advanced performance. The high oxophilicity of Ta ensures a continuous OH– supply, and the bifunctional effect between Ta and Ni accelerates the hydrogen oxidation reaction (HOR). Therefore, Ta-on-NiMo/C exhibited 1.5 times more HOR activity than bare NiMo/C in rotating disk electrode experiments. Furthermore, the effect of Ta as the oxophilic agent was demonstrated by verifying the enhanced performance in a membrane electrode assembly in which Ta-on-NiMo/C was applied as an anodic catalyst.