Metallic glasses or amorphous alloys, with their excellent chemical stability, disordered atomic arrangement, and ability for thermoplastic nanostructuring, show promising performance toward a range of electrocatalytic reactions in proton-exchange membrane fuel cells. However, there are knowledge gaps and a distinct lack of understanding of the role of amorphous alloy chemistry in determining their catalytic activity. Here, we demonstrate the influence of alloy chemistry and the associated electronic structure on the hydrogen oxidation reaction (HOR) activity of a systematic series of Pt42.5-xPdxCu27Ni9.5P21 bulk metallic glasses (BMGs) with x = 0 to 42.5 at%. The HOR activity and electrochemical active surface area as a function of composition were in the form of volcano plots, with a peak around equal proportion of Pt and Pd. The lower relative electron work function and higher binding energy of the Pt core level explain the reduced charge-transfer resistance and improved electrocatalytic activity due to weakened chemisorption of protons in the mid-range composition. Density functional theory calculations show the lower free energy change and higher hydrogen adsorption density for these Pt42.5-xPdxCu27Ni9.5P21 BMGs, suggesting a synergistic effect from the presence of both noble metals, Pt and Pd.
Keywords: density functional theory; electrocatalyst; fuel cell; metallic glass; nanowires.