Hydration‐effect Boosted Active Hydrogen Facilitates Neutral Ammonia Electrosynthesis from Nitrate Reduction

Abstract Electrocatalytic nitrate reduction to ammonia (NO 3 RR) in a neutral medium is a green and effective strategy for treating nitrate pollution meanwhile producing ammonia. However, the insufficient active hydrogen (H * ) on the catalyst surface resulting from the sluggish Volmer step (H 2 O → H + + OH − ), and the competitive hydrogen evolution reaction (HER) caused by H * coupling severely restrict the enhancement of NO 3 RR activity. Herein, a hydration‐effect boosted H * ‐rich strategy facilitating neutral ammonia electrosynthesis from nitrate reduction is proposed. The introduction of the hydration‐effect‐promoting element aluminum into the copper‐based catalyst forming CuAlO 2 , which adjusts the electron density distribution in the catalyst system, and the resulting hydration‐effect significantly promotes the H * generation in a neutral medium. Moreover, the rapid charge transfer at the CuO/CuAlO 2 interface facilitates the reaction kinetics and the H * diffusion. More importantly, the introduction of Al weakens the overly strong adsorption of intermediates by CuO, thereby accelerating the hydrogenation process and suppressing HER. Thus, under neutral conditions, CuO/CuAlO 2 reached a Faradaic efficiency and an ammonia yield as high as 97.81 ± 1.94% and 10.21 ± 0.64 mg h −1 cm −2 at −1.0 V versus RHE toward NO 3 RR.