Ke Wang, Hongzhe Anna Xu, Xin Mao, Xuefei Wang, Min Zheng, Chun-Chuan Kao, Limei Yang, Jiashu Wang, Boming Sun, Shokoofeh Varshooy, Aijun Du, Qi-Long Zhu, Jian Liu, Zhenguo Huang
Electrocatalytic ammonia oxidation reaction (AOR) offers a green route to nitrite (NO2 -) synthesis while coupling hydrogen evolution reaction. However, maintaining NO2 - selectivity at high current density remains challenging due to the narrow thermodynamic windows for NO2 - and nitrate (NO3 -) formation and competition of oxygen evolution reaction at high anodic potentials. Herein, we report a Cu2S/NiOOH heterojunction that sustains high NO2 - selectivity over a wide oxidative window at industrially relevant current densities. Operando Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory calculations reveal that the heterointerface induces interfacial electronic redistribution within the Ni-O framework, strengthens NH3 adsorption, and rebalances AOR energetics, favoring NO2 - release over oxidation. Consequently, in a membrane electrode assembly-based flow cell, Cu2S/NiOOH delivers a Faradaic efficiency for NO2 - (FE(NO2 -)) exceeding 90% at 800 mA cm- 2 with a high production rate of 383.2 mg cm-2 h-1. These results highlight the potential of Cu2S/NiOOH for NO2 - electrosynthesis at industrial production rate.