High Faraday efficiency of Cu₁Co₁-BCN based on a dodecahydro-closo-dodecaborate hybrid for electrocatalytic reduction of nitrate to ammonia

The process of electrocatalytic nitrate reduction reaction (NIRR) to produce ammonia (NH3) presents a promising solution to the challenges of nitrate contamination and high value ammonia synthesis. However, owing to the eight-electron reaction of NIRR, the cathode catalyst type plays a crucial role in governing the NIRR. Herein, Cu1Co1-BCN was prepared as an electrochemical cathode catalyst for the conversion of NO3- to NH3 using a dodecahydro-closo-dodecaborate hybrid (closo-[B12H12](2-)). The catalyst exhibited an excellent ammonia yield (6412.06 mu g h(-1) mgcat(-1)) at -0.5 V versus the reversible hydrogen electrode and a Faraday efficiency (FE) of 92.44%. Additionally, Cu1Co1-BCN exhibited remarkable resistance to interference in 10 mM interfering ion solutions and excellent resistance to acids and bases even at extreme pH levels. It also showed almost no variation in the ammonia yield and FE over ten experimental cycles, thereby indicating its remarkable stability. Furthermore, density functional theory (DFT) calculations confirmed the likelihood of the occurrence of the intermediate step (*N -> *NH), adsorption of NO3-, and desorption of NH3 by Cu1Co1-BCN, thereby facilitating the conversion of NO3- to NH3. These findings offer new insights with regard to designing catalysts for green electrocatalytic ammonia synthesis.