Surface cavity effect on C2H4 formation from electrochemical reduction of CO2 as studied using Cu2O cubes

Surface morphology of Cu-based catalysts is considered as an important factor affecting both activity and product selectivity of electrochemical reduction of CO2. In this work, surface cavity effect on C2H4 formation was investigated using Cu2O cubes: solid cubes, cavity cubes, and broken cubes, typically representing smooth surface, cavity surface, and rough surface. With respect of C2H4 selectivity, cavity cubes show the significantly enhanced faradaic efficiency (FE) of C2H4, 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 CO2 reduction reaction (CO2RR) converted to CH4 and C2H4 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% FEC2 than solid cubes and broken cubes. Our work provides a facile strategy for improving the catalytic C(2+ )product selectivity of Cu2O-based catalysts for CO2RR through modifying surface morphology.

Automated summary

In this study, the surface cavity effect on C2H4 formation was investigated using different types of Cu2O cubes. The results showed that the cavity cubes exhibited significantly enhanced selectivity for C2H4 and higher conversion of CO2 to C2H4 compared to the solid and broken cubes. Moreover, the role of surface cavity was attributed to the increased electrochemical surface area and porous feature, which resulted in higher CO formation and conversion to hydrocarbons and alcohols. The findings suggest that modifying the surface morphology of Cu2O-based catalysts can improve their catalytic selectivity for CO2RR.