Significance of atomically precise copper nanoclusters and their alloys protected by organic monolayer in electrocatalytic carbon dioxide reduction reaction

For tackling the unrestrained emission of carbon dioxide, monolayer-protected metal nanoclusters (MNCs) have garnered much recognition because of their distinct physio-chemical properties (molecular type nature, specific composition, abundant active sites, monodisperse nature, and quantum confinement effects). Although metal nanoparticles (MNPs) have been extensively investigated, MNCs are less frequently investigated, owing to their separation and synthesis problems. Yet, their study is imperative for acquiring structure-performance correlation. Particularly, atomically precise ligand-stabilized copper nanoclusters (Cu-NCs) have fascinated the world not only by their structural grace but also because of their distinct properties. Cu-NCs have been accounted as promising candidates for the transformation of CO₂ into valuable products, especially C₂ products. Given the multi-electron-proton transfer along with the formation of multiple value-added products in electrocatalytic CO₂ reduction reaction (ECO₂RR), an ideal catalyst having high transfer rates and selectivity is demanded. In this perspective, firstly, we have described possible mechanistic routes, followed by the emphasis on the advances of Cu-NCs and their alloys for this model reaction. Subsequently, the significance of hydrides, doping, isomers, coordination mode, metal-core, and quintuple-type ligands has been explored based on experimental evidence supported via theoretical calculations (Density functional theory: DFT). In the penultimate section, we have shed light on the overall role of commonly used ligands, and how electrolytes influence selectivity and activity. Lastly, possible implications along with some future directives have been documented. It is believed that this perspective will disclose this field and pave the way for further evolution of Cu-NCs-based electrocatalysts for identifying the structure-property relationship.