Surface cavity effect on C 2 H 4 formation from electrochemical reduction of CO 2 as studied using Cu 2 O cubes

Surface morphology of Cu-based catalysts is considered as an important factor affecting both activity and product selectivity of electrochemical reduction of CO 2 . In this work, surface cavity effect on C 2 H 4 formation was investigated using Cu 2 O cubes: solid cubes, cavity cubes, and broken cubes, typically representing smooth surface, cavity surface, and rough surface. With respect of C 2 H 4 selectivity, cavity cubes show the significantly enhanced faradaic efficiency (FE) of C 2 H 4 , which is 2.7 and 1.7 times higher than those for solid cubes and broken cubes respectively. Moreover, a ratio of CO produced by CO 2 reduction reaction (CO 2 RR) converted to CH 4 and C 2 H 4 was calculated to assess the extent of CO further reduction for a catalyst. As noted, cavity cubes exhibited a highest ratio of 29.5%, in contrast with the lower ratio of 13.0% on broken cubes and 14.9% on solid cubes. Consequently, the role of surface cavity is reflected in two effects, the increased CO formation due to higher electrochemical surface area as compared to the smooth surface, and meanwhile the increased ratio of CO converted to hydrocarbons and alcohols due to porous feature as compared to the rough surface with a comparable high electrochemical active surface area (ECSA). What’s more, when applied in a flow cell reactor with a gas diffusion electrode, cavity cubes also achieved much higher C2 selectivity of 37.7% FE C2 than solid cubes and broken cubes. Our work provides a facile strategy for improving the catalytic C 2+ product selectivity of Cu 2 O-based catalysts for CO 2 RR through modifying surface morphology. Graphical abstract