High-efficiency ammonia electrosynthesis on self-supported Co2AlO4 nanoarray in neutral media by selective reduction of nitrate

A Co 2 AlO 4 nanosheet array on carbon cloth (Co 2 AlO 4 /CC) is proposed as a superb electrocatalyst for converting nitrate (NO 3 − ) to ammonia (NH 3 ). In 0.1 M PBS solution with 0.1 M NO 3 − , it attains an NH 3 yield of 7.9 mg h −1 cm −2 with a Faradaic efficiency of 92.6%, with high durability. A Zn-NO 3 − battery with such Co 2 AlO 4 /CC as cathode offers a power density of 3.43 mW cm −2 with an NH 3 yield of 750 μg h −1 cm −2 . Theoretical calculations reveal that Al ions reduce the electron cloud density on the surface of Co, making it highly conducive to NO 3 − adsorption at Co sites. Additionally, Co 2 AlO 4 (2   2   0) surface inhibits hydrogen evolution reaction but is highly active for NO 3 − reduction with a low energetically uphill pathway (ΔG of 0.42 eV) for the potential-determining step (*NO 3 to *NO 3 H), much smaller than that of Co 3 O 4 (2   2   0) (ΔG of 0.83 eV).