Atomically Dispersed Copper Electrocatalysts with Proton‐feeding Centers for Efficient Ammonia Synthesis by Nitrate Electroreduction

Abstract

Electrocatalytic conversion of nitrate pollutants into ammonia (NH3) is promising for high‐value chemical production while mitigating environmental pollution. Catalysts play a crucial role in facilitating the necessary chemical reactions, but despite substantial advancements, their efficiency and selectivity remain limited due to the high energy barriers associated with proton transfer. Herein, a unique electrocatalyst system is engineered with isolated copper sites embedded within nitrogen and oxygen co‐doped porous carbon (CuSA‐NO/C). This strategically designed electrocatalyst achieves an impressive NH3 Faradaic efficiency of 92.7% and a yield rate of 24.9 mg h−1 mgCu−1 at a low potential of −0.2 V vs RHE, outperformed most of all previously‐reported atomically dispersed metal‐nitrogen carbon (M‐N‐C) catalysts. The catalytically active site in this electrocatalyst is identified as Cu atom coordinated with two N atoms and two O atoms (CuN2O2). In situ infrared absorption spectroscopy and kinetics isotope experiments revealed that the intrinsic CuN2O2 dramatically enhances the water dissociation process and accelerates the protonation kinetics during nitrate reduction. Furthermore, the first principles calculations show that CuN2O2 catalytic sites also promote the adsorption of NO3− and desorption of NH3, along with the significantly facilitated water dissociation kinetics for proton feeding.