Preanodized Cu Surface for Selective CO 2 Electroreduction to C 1 or C 2+ Products.

The electrochemical CO 2 reduction over Cu catalysts has shown great potential in producing a wide range of valuable chemicals, but it is still plagued by a poor controllability on product distribution. Herein, we demonstrate an effective regulation of CO 2 reduction paths through a preanodization treatment of Cu foil electrodes in different electrolytes. The Cu electrode exhibits a superior C 1 and C 2+ product selectivity after being preanodized in NaClO 4 (Cu- NaClO 4 ) and Na 2 HPO 4 electrolyte (Cu- Na 2 HPO 4 ), respectively. Combined with in situ electrochemical Raman, ATR-SEIRAS, and SEM characterizations, the preferential C 1 path is due to the deposition of many Cu nanocrystals with dominant Cu(111) facets on the Cu- NaClO 4 electrode. In contrast, the preferential C 2+ path over the Cu- Na 2 HPO 4 is attributed to formation of a unique Cu nanodendritic morphology, which strengthens the *CO intermediate adsorption and induces an environment of low local H 2 O/CO 2 stoichiometric ratio, thus facilitating C-C coupling for C 2+ production. Our findings may shed light on the rational control of the CO 2 reduction path through engineering of the Cu surface structure.