Insights of the efficient hydrogen evolution reaction performance in bimetallic Au 4 Cu 2 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 Cu 6 and Au 6 nanoclusters and bimetallic Au 4 Cu 2 nanoclusters. A bimetallic Au 4 Cu 2 /MoS 2 composite exhibits excellent HER catalytic activity with an overpotential ( η 10 ) of 155 mV vs. reversible hydrogen electrode observed at 10 mA cm -2 current density. The improved HER performance in Au 4 Cu 2 is due to the increased electrochemically active surface area (ECSA), and Au 4 Cu 2 NCs exhibits better stability than Cu 6 and Au 6 systems and bare MoS 2 . 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 Au 4 Cu 2 /MoS 2 composite were elucidated, attributing the favorable performance to better electronic interactions occurring at the interface between Au 4 Cu 2 NCs and the MoS 2 substrate. Theoretical analysis reveals that the inherent catalytic enhancement in Au 4 Cu 2 /MoS 2 is due to favorable H atom adsorption over it and the smallest Δ G H* value. The downshift in the d-band of the Au 4 Cu 2 /MoS 2 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.