High Facets on Nanowrinkled Cu via Chemical Vapor Deposition Graphene Growth for Efficient CO2 Reduction into Ethanol

Achieving high electrochemical conversion of carbon dioxide (CO2) into valuable fuels and chemicals is one of the most promising directions to address environmental and energy challenges. Although several single-crystal based studies and simulation results have reported that rich in steps on Cu (100) surfaces are favorable to convert toward C2 alcohol products, most studies are still stuck in low-index (100) facets or surface defect-derived low density of step-sites. In the present work, we report the high production of ethanol by synthesizing a wrinkled Cu catalyst with high facets via a chemical vapor deposition (CVD) graphene growth process. Under our approach, we used graphene as a guiding material to produce wrinkled Cu film for use as an electrocatalyst. The graphene-grown Cu films are not only mass-producible but composed of a high density of step-sites with high-facet atomic arrangements, including the (200) and (310) facets, which are difficult to synthesize using existing methods. The wrinkled Cu film with a unique atomic arrangement showed high ethanol selectivity, achieving 40% faradaic efficiency (FE) at −0.9 V vs reversible hydrogen electrode (RHE), one of the largest selectivity values reported thus far for a Cu-based CO2 conversion catalyst. The C2 selectivity and productivity was 57% FE and −2.2 mA/cm2 at −1.1 V vs RHE, respectively. Density functional theory (DFT) calculation results demonstrated that such a high ethanol productivity is mainly attributable to the (310) facet of the wrinkles, which feature a low C–C coupling barrier (0.5 eV) and a preferred reaction path toward ethanol among other products.