Active sites-rich layered double hydroxide for nitrate-to-ammonia production with high selectivity and stability

Electrochemical nitrate reduction to ammonia (NRA) has attracted increasing attention recently, as it can not only eliminate the harmful nitrate in water, but also produce high value-added ammonia in ambient conditions. Noble metals such as Ru, Pd, Pt, etc., show good activity for NRA but the high price and scarcity restrict their practical applications. Therefore, to develop efficient non-noble metal-based catalysts towards NRA is of great significance. In this contribution, CoFe layered double hydroxide (CoFe LDH) is demonstrated as an efficient non-noble electrocatalyst for NRA. Specifically, NH3 selectivity and Faradaic efficiency of CoFe LDH in alkaline conditions are up to 98.93% and 97.68%, respectively. CoFe LDH also maintains good operation durability during 12 consecutive recycling tests (36 h). It is found that there is strong electronic interaction between Co and Fe species, which accelerates reaction kinetics of CoFe LHD. Density functional theory calculations also suggest that CoFe LDH can favorably promote the adsorption of intermediates (NO3– and NO2–) and desorption of NH3, eventually achieving efficient and selective NH3 production.