From Single Crystal to Single Atom Catalysts: Structural Factors Influencing the Performance of Metal Catalysts for CO2 Electroreduction

With the electrochemical CO2 reduction reaction (CO2RR), CO2 can be used as a feedstock to produce value-added chemicals and fuels while storing renewable energy. For its enormous potential, an extensive research effort has been launched to find the most active electrocatalyst. The reduction of catalyst size has been tested and proven as a key approach to increase the activity of CO2RR while reducing capital cost. However, the catalytic selectivity is not linearly related to the catalyst size due to the influence of many other structural factors. Thus, in-depth knowledge of structure-performance relationships of metal catalysts with different sizes aids in designing efficient electrocatalysts for CO2RR. This Review surveys three decades of research on CO2RR and categorizes various metal catalysts into four size regimes, namely, bulk materials in the form of single crystals, nanoparticles, clusters, and single-atom catalysts. The effects of different structural factors, including crystal facet, coordination environment, metal–support interactions, etc., on the catalysts in each size regime are discussed. Finally, general conclusions are provided with perspectives on future directions for better understanding and further development of active and selective catalysts for CO2RR.