Atomically Precise Mo₂Cu₁₇ Bimetallic Nanocluster: Synergistic Mo₂O₄-Coupled Copper Alkynyl Cluster for the Improved Hydrogen Evolution Reaction Performance

Electrolytic hydrogen production via water splitting holds significant promise for the future of the energy revolution. The design of efficient and abundant catalysts, coupled with a comprehensive understanding of the hydrogen evolution reaction (HER) mechanism, is of paramount importance. In this study, we propose a strategy to craft an atomically precise cluster catalyst with superior HER performance by cocoupling a Mo2O4 structural unit and a Cu(I) alkynyl cluster into a structured framework. The resulting bimetallic cluster, Mo2Cu17, encapsulates a distinctive structure [Mo2O4Cu17(TC4A)(4)(PhC equivalent to C)(6)], comprising a binuclear Mo2O4 subunit and a {Cu-17(TC4A)(2)(PhC equivalent to C)(6)} cluster, both shielded by thiacalix[4]arene (TC4A) and phenylacetylene (PhC equivalent to CH). Expanding our exploration, we synthesized two homoleptic Cu-I alkynyl clusters coprotected by the TC4A and PhC equivalent to C- ligands: Cu-13 and Cu-22. Remarkably, Mo2Cu17 demonstrates superior HER efficiency compared to its counterparts, achieving a current density of 10 mA cm(-2) in alkaline solution with an overpotential as low as 120 mV, significantly outperforming Cu-13 (178 mV) and Cu-22 (214 mV) nanoclusters. DFT calculations illuminate the catalytic mechanism and indicate that the intrinsically higher activity of Mo2Cu17 may be attributed to the synergistic Mo2O4-Cu(I) coupling.