Robust Oxygen‐Vacancy‐Engineered Co(OH) <sub>2</sub> /Cu Heterostructures Boost Nitrate Electroreduction to Ammonia beyond 2 A cm <sup>−2</sup>
Weijie Mei, Chun‐Wai Chang, Zhiguo Li, Xinyu Wang, Yaning Qie, Qi Liu, Ryan C. Davis, Zhitan Wu, Yingjuan Yue, Chenxu Yang, Siqi Li, Daliang Han, Quan‐Hong Yang, Zhenxing Feng, Zhe Weng
Abstract
Abstract Electrocatalytic nitrate reduction reaction (NO 3 RR) presents a sustainable paradigm for green NH 3 synthesis and NO 3 − wastewater valorization. However, overcoming sluggish NO 3 RR kinetics under industrial‐current operation persists as a critical challenge. Herein, robust oxygen vacancy‐enriched heterostructures (O v ‐Co(OH) 2 /Cu) are engineered through in situ electrochemical reconstruction. By coupling Cu‐mediated NO 3 − ‐to‐NO 2 − conversion with O v ‐Co(OH) 2 ‐accelerated NO 2 − ‐to‐NH 3 transformation, this heterostructured system delivers an unprecedented NH 3 yield rate of 167.8 mg h −1 cm −2 and 97.7% Faradaic efficiency at >2 A cm −2 , while maintaining exceptional current tolerance over 25 h. Operando spectroscopic characterizations and theoretical calculations reveal that the introduction of O v in Co(OH) 2 synergistically accelerates water dissociation to ensure continuous hydrogen supply and optimizes * NOOH adsorption, reducing the energy barrier for the rate‐limiting step ( * NO 2 to * NOOH). To demonstrate practical viability, a membrane‐electrode‐assembly electrolyzer integrating NO 3 RR with glycerol oxidation reaction achieves highly effective co‐production of NH 3 and formate alongside wastewater treatment. This work offers new insights into the rational design of electrocatalysts through in situ reconstruction‐induced vacancy engineering for scalable and practical NO 3 RR applications.