Promoting *NO 2 Hydrogeneration on Cobalt‐Doped Copper Oxides for Selective Ammonia Electrosynthesis from Nitrate

Abstract Electrochemical nitrate reduction reaction (NO 3 RR) driven by renewable energy has attracted extensive attention, which can realize nitrate degradation and ammonia production simultaneously under ambient conditions. Copper−based catalysts are the most widely used due to their high activity but are subject to low selectivity owing to intermediate nitrite accumulation. This work has reported cobalt‐doped copper oxide (Co/CuO) composites, while introduced Co sites accelerate the hydrogenation of nitrogen species. The prepared Co/CuO composites realize a 93.9 % Faradaic efficiency at the applied potential of −0.4 V (vs. RHE), yielding ammonia at 0.5441 mmol⋅h −1 cm −2 . The exceptional stability of Co/CuO composites has also been affirmed by following continuous recycling tests. In situ characterization confirms that the existence of Co sites is prone to conversion of * NO 2 to * NH 2 , thus exhibiting high performance for NO 3 RR.