Atomically precise thiolate protected hexanuclear silver nanoclusters [Ag6(PMBI)6] as an efficient catalyst for the hydrogen evolution reaction

Abstract

Metal nanoclusters (MNCs) with atomic precision and well-defined structures are gaining attention for various applications. In this work, we present the synthesis and structure of a novel thiolate-protected silver nanocluster with the molecular formula Ag₆(PMBI)₆, where PMBI denotes 9-propyl-2-mercaptobenzimidazole. The nanocluster was synthesized using a one-pot approach, and its structure was determined using single-crystal X-ray diffraction (SC-XRD). SC-XRD analysis further revealed a well-defined Ag₆ core coordinated by six thiolate ligand units, forming a symmetric molecular cluster. Ligand engineering of silver nanoclusters enhances stability and modulates the physical and chemical properties of clusters, transforming them into efficient electrocatalysts for the hydrogen evolution reaction (HER). We investigated the nanoclusters' electrocatalytic HER activity under alkaline conditions. It exhibited an overpotential of 197 mV at 10 mA cm⁻² and a Tafel slope of 125.3 mV dec⁻¹. In addition, Ag₆(PMBI)₆ shows negligible toxicity, indicating its environmental and biological safety. This study showcases the potential of silver nanoclusters as a cost-effective and scalable HER electrocatalyst, providing an alternative to classical platinum-based electrocatalysts.