Ampere-level current density ammonia electrochemical synthesis using CuCo nanosheets simulating nitrite reductase bifunctional nature.

The development of electrocatalysts capable of efficient reduction of nitrate (NO ₃ ^- ) to ammonia (NH ₃ ) is drawing increasing interest for the sake of low carbon emission and environmental protection. Herein, we present a CuCo bimetallic catalyst able to imitate the bifunctional nature of copper-type nitrite reductase, which could easily remove NO ₂ ^- via the collaboration of two active centers. Indeed, Co acts as an electron/proton donating center, while Cu facilitates NO _x ^- adsorption/association. The bio-inspired CuCo nanosheet electrocatalyst delivers a 100 ± 1% Faradaic efficiency at an ampere-level current density of 1035 mA cm ^-2 at -0.2 V vs. Reversible Hydrogen Electrode. The NH ₃ production rate reaches a high activity of 4.8 mmol cm ^-2 h ^-1 (960 mmol g _cat ^-1 h ^-1 ). A mechanistic study, using electrochemical in situ Fourier transform infrared spectroscopy and shell-isolated nanoparticle enhanced Raman spectroscopy, reveals a strong synergy between Cu and Co, with Co sites promoting the hydrogenation of NO ₃ ^- to NH ₃ via adsorbed *H species. The well-modulated coverage of adsorbed *H and *NO ₃ led simultaneously to high NH ₃ selectivity and yield.
(© 2022. The Author(s).)