Electron Delocalization-Induced Modulation of Rate-Determining Step of Copper Catalyst for Efficient Ammonia...

Electrochemical NO_x^- reduction offers an attractive approach for the sustainable production of ammonia (NH₃). Copper (Cu)-based materials are commonly used catalysts but suffer from a complex reaction pathway and low NH₃ selectivity. Herein, we report an electron delocalization strategy by inducing oxygen vacancy and chlorine (Cl) coordination sites as a dual modulator for the active Cu sites. Our model catalyst (Cu₂O_1-xCl₂) could deliver high NH₃ yields over a wide potential window, with a maximum NH₃ yield rate of 10.05 mg h^-1 cm^-2 and a Faradaic efficiency (FE) of 95.1%, exceeding most reported metal catalysts. A combination of experimental and theoretical investigations reveals that the dual modulator induces a favorable electron delocalization around the active Cu sites, resulting in an alteration of the rate-determining step (RDS) from NO₂* hydrogenation to the one proton-electron coupling of NO* to form NOH*. This thus enables rapid hydrogenation, avoids the occurrence of side reactions, and significantly improves the selectivity and yield of NH₃. When assembled into a membrane electrode electrolyzer, the cell can achieve an industrial current density of 340 mA cm^-2 with an NH₃ production rate of about 21.36 mg h^-1 cm^-2 and stably operates for up to 200 h. This RDS regulation strategy provides an innovative solution for enhancing the selectivity and efficiency of target products in electrocatalysis.