Efficient electrocatalytic nitrate-to-ammonia conversion on CoCu bimetallic electrodes under near-neutral conditions

The electrocatalytic reduction of nitrate for its highly selective conversion to ammonia can be regarded as an efficient nitrate removal and resource recovery technology. CoCu bimetal electrodes were fabricated via electrodeposition combined with in-situ annealing. The effects of the metal ratio in the deposition solution, applied potential, and initial pH on the catalyst performance were systematically investigated. The results demonstrate that under near-neutral conditions (pH = 6), at an applied potential of −0.60 V vs RHE and a Cu∶Co ratio of 5∶5 in the deposition solution, the catalyst exhibited optimal performance. This included a \textNO_\text3^-\text-N removal rate of 97.80%, an \textN\textH_\text3\text-N yield rate of 2824.85 μg·h⁻¹·cm⁻², a Faradaic efficiency of 93. 22%, and an \textN\textH_\text3\text-N selectivity of 97.10%. Scavenger experiments confirmed that the active hydrogen atoms (*H) generated via hydrolysis during the reaction are key intermediates. Mechanism studies reveal that Co and Cu sites synergistically catalyze the reaction: Cu sites preferentially adsorb and rapidly convert \textNO_\text3^-\text-N into the intermediate \textNO_\text2^-\text-N , while Co sites effectively promote the deoxygenation and hydrogenation of \textNO_\text2^-\text-N to generate \textN\textH_\text3\text-N . Density functional theory calculations indicate that Co doping significantly reduces the energy barrier for *H generation. This synergistic effect markedly enhances the activity and selectivity of the catalyst, providing valuable insights for nitrate pollution control.