Crystal facet-dependent electrocatalytic performance of metallic Cu in CO2 reduction reactions

Developing high-performance electrocatalysts for CO2 reduction reaction (CO2RR) is crucial since it is beneficial for environmental protection and the resulting value-add chemical products can act as an alternative to fossil feedstocks. Nonetheless, the direct reduction of CO2 into long-chain hydrocarbons and oxygenated hydrocarbons with high selectivity remains challenging. Copper (Cu) shows a distinctive advantage that it is the only pure metal catalyst for reducing CO2 into multi-carbon (C2+) products and the certain facets (e.g., (100), (111), (111)) of Cu nanocrystals exhibit relatively low energy barriers for the formation of specific products (e.g., CO, HCOOH, CH4, C2H4, C2H5OH, and other C2+ products). Therefore, extensive studies have been carried out to explore the relationship between the facets of Cu nanocrystals and corresponding catalytic products. In this review, we will discuss the crystal facet-dependent electrocatalytic CO2RR performance in metallic Cu catalysts, meanwhile, the detailed reaction mechanisms will be systematically summarized. In addition, we will provide a personal perspective for the future research directions in this emerging field. We believe this review is helpful to guide the design of high-selectivity Cu-based electrocatalysts for CO2RR.