Coordination effect modulates surface metal coverage for boosting nitrate electroreduction to ammonia

Electrocatalytic nitrate reduction reaction (NO 3 − RR) is expected to sustainably produce green ammonia and treat nitrate-containing wastewater by renewable energy. NO 3 − RR involves a complex multi-step pathway starting from nitrate adsorption to subsequent hydrogenation reactions by active hydrogen (*H). However, the simultaneous optimization of NO 3 − adsorption and *H supply by present modulation strategies of supported metal catalyst is still challenging. Herein, we utilize the coordination effect to effectively modulate surface metal coverage of metal oxide support to balance NO 3 − adsorption and *H generation for boosting NO 3 − RR performance. Experimental and theoretical results reveal that the electron-deficient Cu δ+ of CoO with low surface Cu coverage (Cu LC -CoO) shows strong adsorption towards NO 3 − and the exposed CoO support can disturb interfacial hydrogen bond network to promote H 2 O dissociation and *H generation for hydrogenation reduction of NO 3 − . Therefore, Cu LC -CoO catalyst shows an attractive Faradaic efficiency of 98.0%, and a high NH 3 yield rate of 170.3 mg h −1 cm −2 at an industrial-relevant current density over 2 A cm −2 . Furthermore, the NO 3 − RR||HzOR coupling system is constructed by using Cu LC -CoO as bifunctional catalyst to produce ammonia with low energy consumption of 8.5 kWh k g N H 3 −1 for 100 cycles, and the commercialization value of the NO 3 − RR||HzOR system is demonstrated by techno-economic analysis.