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

A Co2AlO4 nanosheet array on carbon cloth (Co2AlO4/CC) is proposed as a superb electrocatalyst for converting nitrate (NO3-) to ammonia (NH3). In 0.1 M PBS solution with 0.1 M NO3-, it attains an NH3 yield of 7.9 mg h(-1) cm(-2) with a Faradaic efficiency of 92.6%, with high durability. A Zn-NO3- battery with such Co2AlO4/CC as cathode offers a power density of 3.43 mW cm(-2) with an NH3 yield of 750 mu g 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 NO3- adsorption at Co sites. Additionally, Co2AlO4 (220) surface inhibits hydrogen evolution reaction but is highly active for NO3- reduction with a low energetically uphill pathway (& UDelta;G of 0.42 eV) for the potential-determining step (*NO3 to *NO3H), much smaller than that of Co3O4 (220) (& UDelta;G of 0.83 eV).

Automated summary

A Co2AlO4 nanosheet array on carbon cloth is proposed as an excellent electrocatalyst for converting nitrate to ammonia. The experimental results show that this electrocatalyst has high yield and efficiency in the process of nitrate conversion to ammonia.