Complementary Operando Spectroscopy identification of in-situ generated metastable charge-asymmetry Cu₂-CuN₃ clusters for CO₂ reduction to ethanol.

Abstract

Copper-based materials can reliably convert carbon dioxide into multi-carbon products but they suffer from poor activity and product selectivity. The atomic structure-activity relationship of electrocatalysts for the selectivity is controversial due to the lacking of systemic multiple dimensions for operando condition study. Herein, we synthesized high-performance CO₂RR catalyst comprising of CuO clusters supported on N-doped carbon nanosheets, which exhibited high C₂₊ products Faradaic efficiency of 73% including decent ethanol selectivity of 51% with a partial current density of 14.4 mA/cm^-2 at -1.1 V vs. RHE. We evidenced catalyst restructuring and tracked the variation of the active states under reaction conditions, presenting the atomic structure-activity relationship of this catalyst. Operando XAS, XANES simulations and Quasi-in-situ XPS analyses identified a reversible potential-dependent transformation from dispersed CuO clusters to Cu₂-CuN₃ clusters which are the optimal sites. This cluster can't exist without the applied potential. The N-doping dispersed the reduced Cu_n clusters uniformly and maintained excellent stability and high activity with adjusting the charge distribution between the Cu atoms and N-doped carbon interface. By combining Operando FTIR and DFT calculations, it was recognized that the Cu₂-CuN₃ clusters displayed charge-asymmetric sites which were intensified by CH₃^* adsorbing, beneficial to the formation of the high-efficiency asymmetric ethanol.