Hydrogen Oxidation Reaction Response of Noble-Metal Based Bulk Metallic Glasses

Abstract: Noble-metal based metallic glasses have recently shown excellent performance towards a range of catalytic reactions, which is attributed to their disordered atomic structure and high density of active sites on the surface. An in-depth understanding of the mechanisms that promote the catalytic performance of amorphous alloys would facilitate the design and development of highly efficient catalysts with significantly lower precious metal loading. In the present study, the electro-catalytic behavior of amorphous Pt- and Pd-based metallic glasses was studied towards hydrogen oxidation reaction by cyclic voltammetry and scanning electrochemical microscopy. The electrochemically active surface area for the metallic glasses was found to be several folds higher compared to pure Pt and Pd. Density functional theory calculations showed that hydrogen oxidation on the surface of the amorphous alloys preferentially followed the reverse Heyrovsky-Volmer pathway. The minimum over-potential for the amorphous alloys was calculated to be significantly lower compared to pure Pt and Pd, consistent with the experimental trends. The enhanced catalytic activity for the amorphous alloys was attributed to the reduced chemisorption of hydrogen on the metallic glass surface, particularly for the alloys containing both Pt and Pd.