Non-Innocent Role of Porous Carbon Toward Enhancing C2-3 Products in the Electroreduction of Carbon Dioxide.

Selectivity for C-C coupled products remains a major challenge for electrochemical CO2 reduction. Herein, we report a facile method by modifying a Cu foil surface with a layer of porous carbon. The structure of carbon has a major influence on C1 and C2,3 product selectivity. A carbon aerogel modifier leads to higher C2,3 product formation than that of a carbon black modifier, demonstrating the non-innocent role of carbon materials. In both cases, major surface reconstruction on the Cu foil-such as pitting and particle formation-is observed during electrocatalysis. In addition, the restructured Cu surface shows distinctly lower activity toward CO2 reduction when the carbon modifier is removed. This is likely due to the fact that the carbon modifiers influence the product distribution by (i) modulating the local pH and CO2 concentration by serving as a highly porous and hydrophobic barrier, and (ii) restructuring the metal surface that generates more active sites. Our findings illustrate that the carbon in carbon-based catalysts can have an disproportionate role in directing product formation in electrocatalytic carbon dioxide reduction.