Size‐Dependent Carbon Dioxide Reduction Activity of Copper Nanoparticle and Nanocluster Electrocatalysts

Abstract The electrochemical carbon dioxide (CO₂) reduction reaction (CRR, which can convert CO₂ into useful compounds at room temperature and ambient pressure by using electricity derived from renewable energy source), has been attracting attention in recent years. This is because it can convert CO₂ into useful compounds, which is pertinent to establishing a next‐generation recycling‐oriented energy society. However, further improvement of the electrocatalyst is required to improve its activity, selectivity, and durability. Among these, copper (Cu) can synthesize various hydrocarbons from CO₂ and has been the most studied electrocatalyst for the CRR over many years. In particular, regarding ligand‐protected Cu particles for the CRR, the size, shape, and ligands of Cu particles prepared by chemical reduction can be precisely controlled. In this review, we summarize previous research on the size‐dependence of the CRR by using ligand‐protected Cu particles (nanoparticles and nanoclusters) prepared by liquid‐phase reduction, and discuss the current status of these studies for researchers on the electrochemical CRR.