Advances in coinage metal nanoclusters: From synthesis strategies to electrocatalytic performance

As a result of the powerful quantum confined space effects and multiple modes of very tiny atomic sizes, metal nanoclusters (NCs) that consist of thiolate-protected noble metals, such as silver (Ag) and gold (Au) have core sizes less than 3 nm, have emerged as a class of "metallic molecules" with a wide range of molecule-like optical, magnetic, and electronic properties. To investigate well-defined nanocatalysts, especially ligand-passivated metal nanoclusters, great strides have been achieved in the efficient synthesis of atomically precise nanoparticles. Methods of synthesis such as bottom-up growth, top-down approach, ligand engineering, and the interconversion system are covered in this overview. Such clearly defined metal nanoclusters have demonstrated considerable promise in catalysis research and have evolved into a distinct class of model catalysts. Focusing on the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and oxygen evolution reaction (OER), this article attempts to outline current developments in nanoclusters of molecular metal employed in electrocatalytic reactions. The paper also highlights the connection between the catalytic mechanism's structure and performance as well as examines the potential effects of metal clusters' sizes, metal core structures, charges, ligands, and metal-ligand binding patterns on their electrocatalytic activity. Future research opportunities and challenges are also proposed.