Composition-dependent hydrogen evolution performance of Au-Pt nanoparticles: Correlating catalytic activity and first-principles calculations

In this study, a series of Au-Pt bimetallic nanoparticles (NPs) with varying compositions (Au, Au-3-Pt-1, Au-1-Pt-1, Au-1-Pt-3) were synthesized via a modified polyol method and systematically investigated for their structural, morphological, and electrocatalytic properties toward the hydrogen evolution reaction (HER). Rietveld refinement of powder XRD data revealed a progressive lattice contraction, crystallite size reduction, and increasing microstrain with increasing Pt content, indicating partial alloying and phase segregation. High-resolution TEM and HAADF-EDS mapping confirmed the formation of core-shell, ball-cup, or Janus-type nanostructures, with Pt preferentially located at the periphery of Au-rich cores. DFT calculations corroborated the experimental findings, revealing negative excess energies for these morphologies and identifying ball-cup and Janus configurations as energetically favorable at equiatomic and Pt-rich compositions in Au-Pt nanoalloys. Electrochemical measurements in 1 M KOH showed enhanced HER activity for bimetallic systems, with Au-1-Pt-1 exhibiting the lowest overpotential (9 mV at 25 mA cm(-2)), and Au-1-Pt-3 demonstrating the highest specific (70.35 mA cm(-2)) and mass (268.56 mA mgPt(-1)) activities. Tafel slope analyses and turnover frequency calculations confirmed improved kinetics and Pt utilization efficiency. The superior stability over 500 CV cycles and favorable hydrogen adsorption energetics, as supported by DFT, highlight the potential of Au-Pt nanostructures as high-performance, durable HER electrocatalysts.