Enhanced CO₂ Electroreduction to Multi-Carbon Products on Copper via Plasma Fluorination

The electroreduction of carbon dioxide (CO₂) to multi-carbon (C₂₊) compounds offers a viable approach for the up-conversion of greenhouse gases into valuable fuels and feedstocks. Nevertheless, current industrial applications face limitations due to unsatisfactory conversion efficiency and high overpotential. Herein, a facile and scalable plasma fluorination method is reported. Concurrently, self-evolution during CO₂ electroreduction is employed to control the active sites of Cu catalysts. The copper catalyst modified with fluorine exhibits an impressive C₂₊ Faradaic efficiency (FE) of 81.8% at a low potential of -0.56 V (vs a reversible hydrogen electrode) in an alkaline flow cell. The presence of modified fluorine leads to the exposure and stabilization of high-activity Cu⁺ species, enhancing the adsorption of *CO intermediates and the generation of *CHO, facilitating the subsequent dimerization. This results in a notably improved conversion efficiency of 13.1% and a significant reduction in the overpotential (≈100 mV) for the C₂₊ products. Furthermore, a superior C₂₊ FE of 81.6% at 250 mA cm^-2, coupled with an energy efficiency of 31.0%, can be achieved in a two-electrode membrane electrode assembly electrolyzer utilizing the fluorine-modified copper catalyst. The strategy provides novel insights into the controllable electronic modification and surface reconstruction of electrocatalysts with practical potential.