Cu nanosheets with exposed (111) crystal facets for highly efficient electrocatalytic CO2 reduction reaction toward methanol production†

The exposed crystal facets of Cu have a profound effect on its electrocatalytic CO₂ reduction reaction (CO₂RR) activity and product selectivity. On the other hand, at present, most of the studies on Cu-based electrocatalysts for the CO₂RR focus on the synthesis of C₂₊ products. There are only a few reports involving methanol (CH₃OH) generation over Cu nanocrystals. Herein, CuO nanosheets (NSs) and nanorods (NRs) were synthesized through a controlled oxidation and dehydration route under mild reaction conditions, using Cu mesh as a Cu source and conductive substrate, respectively. The as-synthesized CuO NSs and NRs were further converted into Cu NSs and NRs through an in situ electrochemical reduction method, respectively. The experimental results showed that CH₃OH could be efficiently produced over Cu NSs with abundant (111) crystal facets through the electrocatalytic CO₂RR. The maximum CH₃OH faradaic efficiency (FE) obtained on Cu NSs is 68% at a relatively low applied potential of −0.6 V vs. reversible hydrogen electrode (RHE), which is 1.6 times larger than that achieved on Cu NRs with primarily exposed (200) crystal facets (42%). The crystal facet-dependent electrocatalytic CO₂RR activity toward CH₃OH production was elucidated based on theoretical calculations combined with experimental results.