Effects of Metal-Doping on Hydrogen Evolution Reaction Catalyzed by MAu₂₄ and M₂Au₃₆ Nanoclusters (M = Pt, Pd)

This paper describes the effects of doped metals on hydrogen evolution reaction (HER) electrocatalyzed by atomically controlled MAu₂₄ and M₂Au₃₆ nanoclusters, where M = Pt and Pd. HER performances, such as onset potential ( E_onset), catalytic current density, and turnover frequency (TOF), are comparatively examined with respect to the doped metals. Doping Pt or Pd into gold nanoclusters not only changes the electrochemical redox potentials of nanoclusters but also considerably improves the HER activities. E_onset is found to be controlled by the nanocluster's reduction potential matching the reduction potential of H⁺. The higher catalytic current and TOF are observed with the doped nanoclusters in the order of PtAu₂₄ > PdAu₂₄ > Au₂₅. The same trend is observed with the Au₃₈ group (Pt₂Au₃₆ > Pd₂Au₃₆> Au₃₈). Density functional theory calculations have revealed that the hydrogen adsorption free energy (Δ G_H) is significantly lowered by metal-doping in the order of Au₂₅ > PdAu₂₄ > PtAu₂₄ and Au₃₈ > Pd₂Au₃₆ > Pt₂Au₃₆, indicating that hydrogen adsorption on the active site of nanocluster is thermodynamically favored by Pd-doping and further by Pt-doping. The doped metals, albeit buried in the core of the nanoclusters, have profound impact on their HER activities by altering their reduction potentials and hydrogen adsorption free energies.