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

Due to the powerful quantum confined space effects and multiple modes of small atomic sizes, metal nanoclusters (NCs) like thiolate-protected noble metals, such as silver (Ag) and gold (Au), which have a core sizes less than 3 nm, have developed a class of "metallic molecules" with multiple optical, magnetic, and electronic properties. To find a well-defined nanocatalysts, especially ligand-passivated metal NCs, 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 interconversion system, are mentioned in this overview. Such clearly defined metal NCs 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 NCs of molecular metals employed in electrocatalytic reactions. The paper highlights the relationship between the structure and performance of the catalytic mechanism and examines the potential effects of metal cluster sizes, metal core structures, charges, ligands, and metal–ligand binding patterns on their electrocatalytic activity. Future research opportunities and challenges are also proposed.