Promoting C2+ Production from Electrochemical CO2 Reduction on Shape-Controlled Cuprous Oxide Nanocrystals with High-Index Facets

Morphology- and crystal facet-controlled Cu2O nanocrystals (NCs), including cubic Cu2O (c-Cu2O) NCs with {100} facets, rhombic dodecahedral Cu2O (d-Cu2O) NCs with {110} facets, and concave octahedral Cu2O (o-Cu2O) NCs with high-index facets, are prepared and employed as catalysts for the electrochemical reduction of CO2 to C2+ products (ethylene, ethanol, and n-propanol). In situ Raman characterizations demonstrate that the surfaces of all three Cu2O NCs are rapidly converted to metallic Cu during CO2 reduction and reoxidized to smaller-sized Cu2O NCs after tests. Specifically, the o-Cu2O catalyst reveals the highest Faradaic efficiency (48.3%) and partial current density (17.7 mA cm–2) for C2+ products at −1.1 V versus reversible hydrogen electrode compared to c-Cu2O and d-Cu2O, which is competitive among the reported Cu and Cu2O catalysts. In addition, abundant crystal defects/grain boundaries and high-index facets are observed on the surface of reconstructed o-Cu2O, which may serve as the active sites and benefit the C–C coupling during CO2 reduction. This work provides a new strategy to achieve efficient C2+ production from electrochemical CO2 reduction via crystal facet regulation of Cu2O catalysts.