AuPdPt Ternary Alloy Nanoparticles for Highly Active Hydrogen Evolution Reaction.

Alloying is effective for enhancing the hydrogen evolution reaction (HER) activity of Pt. Binary PdPt alloys outperform monometallic Pt in terms of HER activity. However, their HER activity can be improved further by incorporating a third element. In this study, we demonstrate that incorporating Au into PdPt alloys alters their electronic structures, enhancing their HER activity. Homogeneous solid-solution Au₂₀Pd₄₀Pt₄₀ alloy nanoparticles (NPs) were synthesized using a one-pot polyol method. Elemental mapping using scanning transmission electron microscopy (STEM) combined with energy-dispersive X-ray spectroscopy confirmed the uniform distribution of the three elements within the NPs, demonstrating the formation of a solid-solution alloy. X-ray absorption near-edge structure analysis indicated electron transfer from Au to Pt and Pd, which generated a more reduced electronic state of Pt compared to that in the Pd₅₀Pt₅₀ alloy NPs. Electrochemical measurements in 0.5 M H₂SO₄ revealed that Au₂₀Pd₄₀Pt₄₀ alloy NPs had a lower overpotential (15.4 mV at 10 mA cm^-2) and a higher intrinsic turnover frequency (TOF) than Pd₅₀Pt₅₀ alloy and monometallic Pt NPs. These findings demonstrate that homogeneously mixing a third element into binary alloy NPs is effective for enhancing the catalytic performance.