A Review on the Influence of Crystal Facets on the Product Selectivity of CO₂RR over Cu Metal Catalysts

The electrocatalytic carbon dioxide reduction reaction (ECRR) is promising in converting environmentally harmful CO₂ into useful chemicals, but the large-scale application of this technology is seriously limited by its low efficiency and selectivity. Cu-based electrocatalysts displayed attractive ability in converting CO₂ to multiple products, and the product selectivity can be manipulated through various approaches. Among them, exposing specific crystal facets through crystal facet engineering has been proven to be highly effective in obtaining specific products and has attracted numerous researchers. However, to our knowledge, few reports have systematically summarized the relationship between the crystal facet control of Cu catalysts and the catalytic products. This review begins by outlining the general mechanism of CO₂ electrocatalytic reduction on Cu-based catalysts, and then summarizes the preferences of low-index and high-index Cu facets regarding product selectivity and delves into the synergistic effects between facets (including different Cu facets and interactions between Cu and non-Cu facets) and their impact on CO₂ reduction reaction (CO₂RR). In addition, the study of the recently developed Cu single-atom catalysts in ECRR was also introduced. Finally, we provide an outlook on the development of high-performance Cu-based catalysts for applications in CO₂RR. The purpose of this review is to provide a clear vein and meaningful guidance for the following studies over the crystal facet control of Cu-based electrocatalysts.