Robust\nCu<sub>2</sub>O/CuS Heterostructured Cu<sub>40</sub> Nanoclusters\nfor Electrocatalytic Hydrogen Evolution

Metal\noxide/metal chalcogenide heterostructure materials have garnered\nintensive attention in both fundamental research and practical applications,\nparticularly in the field of catalysis. For example, the Cu<sub>2</sub>O/CuS heterostructures have found wide applications in electrocatalysis\nand photoelectrocatalysis. Despite their wide-ranging applications,\nthe atomic-level insight into the interfacial structures of Cu<sub>2</sub>O/CuS heterostructure materials and the effect of such interface\non catalysis has remained a longstanding challenge. Herein, we present\na comprehensive illustration of Cu<sub>2</sub>O/CuS heterostructures\nthrough the complete structural determination of an atomically precise\ncopper nanocluster, Cu<sub>40</sub>O<sub>8</sub>(<sup>t</sup>BuS)<sub>24</sub> (<sup>t</sup>BuSH is 2-methyl-2-propanethiol) whose structure\ndescribes the stabilization of Cu<sub>4</sub>O tetrahedra by −S–Cu–S–\nunits. Notably, the cluster has been prepared in one pot under ambient\nconditions and exhibits exceptional stability when subjected to heat\nand highly concentrated acid (1 M HCl) or base (1 M KOH), respectively.\nImportantly, the cluster exhibits outstanding activity in the electrocatalytic\nhydrogen evolution reaction (HER), surpassing the performance of most\nreported copper nanoclusters with an overpotential of 90 mV at 10\nmA/cm<sup>2</sup>. Both the experimental and theoretical investigations\nsuggest that the heterostructures of the cluster play a pivotal role\nin enhancing its electrocatalytic HER activity. This work not only\nprovides crucial insights into the long-pursued interfacial structures\nof Cu<sub>2</sub>O/CuS heterostructure materials but also paves the\nway for the fabrication of atomically precise metal nanoclusters featuring\nmetal oxide/metal chalcogenide heterostructures.