Cooperative Cu with defective MXene for enhanced nitrate electroreduction to ammonia

Abstract The electroreduction of nitrate (NO3RR) to ammonia (NH3) provides a promising solution to enable environmental remediation caused by ‐containing waste and also allows for energy‐saving NH3 generation. Adsorption of *NO2 intermediate may be strengthened to decrease byproducts (e.g., ) and favor the eight‐electron NO3RR into NH3. In this work, copper‐incorporated O‐vacancy containing Ti3C2 MXene (Cu@Ti3C2Ov) is reported, which cooperatively inhibits production and facilitates hydrogenation, leading to approximately 100% Faradaic efficiencies of NH3 and high yield rates at various potentials. Density functional theory calculations show that and the *NO2 intermediates have a significant interaction with the Cu@Ti3C2Ov catalyst. Moreover, the formation of has a high energy barrier, which explains the appealing catalytic performance of the Cu@Ti3C2Ov toward NO3RR with suppressed and elevated NH3 selectivity. This work would motivate the prudent design of new catalysts for high‐performance NO3RR to NH3 by elucidating the significance of stabilizing the *NO2 intermediate.