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–x
Pd
x
Cu27Ni9.5P21 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–x
Pd
x
Cu27Ni9.5P21 BMGs, suggesting
a synergistic effect from the presence of both noble metals, Pt and
Pd.