Synergistic CuO@Ni(OH) Core-Shell Electrocatalyst for High-Efficiency Nitrate Reduction to Ammonia.

The electrocatalytic reduction reaction of nitrate (NORR) is anticipated to convert nitrogen-containing pollutants into valuable ammonia products. Copper-based catalysts have received great attention because of their good performance in the NORR due to the strong binding energy with *NO intermediates. However, the poor HO dissociation ability of Cu is unable to provide H in time for the hydrogenation reaction of NO, thus hindering the electroreduction of the NO. Herein, we designed a shell-core nanocube electrocatalyst CuO@Ni(OH)- ( represents the molar ratio of Ni/Cu) using the liquid phase reduction combined with the etching and precipitation method for electrocatalytic NORR. Due to the synergistic effect between the strong nitrate activation ability of Cu and the excellent HO dissociation ability of Ni(OH), CuO@Ni(OH)-3.3% shows an impressive ammonia yield rate (557.9 μmol h cm) and Faradaic efficiency (97.4%) at -0.35 V vs. RHE. Operando Raman and Auger electron spectroscopy observe the reduction of CuO to Cu during the NORR process. Density functional theory calculations combined with electron paramagnetic resonance analysis reveals that Ni(OH) can lower the activation energy barrier of HO dissociation, thereby promoting the generation of H and accelerating the hydrogenation of *NO during the NORR. This research provides an efficient Cu-based catalyst for reducing NO and may motivate the development of effective ammonia electrocatalysts for further experimentation.