Precise Synthesis of Ligand-Protected Metal Nanoclusters for Electrochemical/Photoelectrochemical Applications

Ligand-protected metal nanoclusters (NCs) represent a significant advancement in the field of catalysis due to their unique size-specific electronic and geometric structures. These properties are highly dependent on the metal species, number of constituent atoms, and geometric structure of the metal NC. We discuss on the synthesis, stability, structural characterization, and electrocatalytic/photocatalytic applications of these fascinating materials, emphasizing their superior performance over conventional catalysts. In this study, we have obtained a deeper understanding of the interaction between the metal core and the organic ligands protecting the metal NCs, as well as the desorption behavior of the ligands under calcination, which is crucial for the application of metal NCs as heterogeneous catalysts. Based on this understanding, we have demonstrated that metal NCs-supported catalysts with appropriate pretreatment exhibit higher activity as photocatalysts compared to conventional catalysts. Moreover, by suppressing oxygen poisoning through the use of sulfur species in the ligands, Pt NCs showed high activity as cocatalysts for photocatalytic hydrogen evolution in water splitting. Additionally, atomically precised phosphine-protected Pt NCs exhibited high activity as cathode electrocatalysts for fuel cells. These findings are expected to significantly contribute to the development of more diverse catalysts based on metal NCs, including those with varying metal species, numbers of constituent atoms, and geometric structures.