Insights of the efficient hydrogen evolution reaction performance in bimetallic Au₄Cu₂ nanoclusters

The design of efficient electrocatalysts for improving hydrogen evolution reaction (HER) performance using atomically precise metal nanoclusters (NCs) is an emerging area of research. Here, we have studied the HER electrocatalytic performance of monometallic Cu₆ and Au₆ nanoclusters and bimetallic Au₄Cu₂ nanoclusters. A bimetallic Au₄Cu₂/MoS₂ composite exhibits excellent HER catalytic activity with an overpotential (η₁₀) of 155 mV vs. reversible hydrogen electrode observed at 10 mA cm^-2 current density. The improved HER performance in Au₄Cu₂ is due to the increased electrochemically active surface area (ECSA), and Au₄Cu₂ NCs exhibits better stability than Cu₆ and Au₆ systems and bare MoS₂. This augmentation offers a greater number of active sites for the favorable adsorption of reaction intermediates. Furthermore, by employing X-ray photoelectron spectroscopy (XPS) and Raman analysis, the kinetics of HER in the Au₄Cu₂/MoS₂ composite were elucidated, attributing the favorable performance to better electronic interactions occurring at the interface between Au₄Cu₂ NCs and the MoS₂ substrate. Theoretical analysis reveals that the inherent catalytic enhancement in Au₄Cu₂/MoS₂ is due to favorable H atom adsorption over it and the smallest ΔG_H* value. The downshift in the d-band of the Au₄Cu₂/MoS₂ composite influences the binding energy of intermediate catalytic species. This new catalyst sheds light on the structure-property relationship for improving electrocatalytic performance at the atomic level.