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

Abstract

Electrocatalytic nitrate reduction to ammonia (NO3RR) 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 (H2O → H+ + OH−), and the competitive hydrogen evolution reaction (HER) caused by H* coupling severely restrict the enhancement of NO3RR 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 CuAlO2, 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/CuAlO2 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/CuAlO2 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 NO3RR.