Abstract
Co2AlO4/CC achieves superb NO3− reduction performances with a large NH3 yield of 7.9 mg h−1 cm−2 and a Faradaic efficiency of 92.6%. Furthermore, the Co2AlO4/CC-based Zn-NO3− battery offers a high power density and a large NH3 yield.
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•A Co2AlO4 nanosheet array acts as a 3D electrocatalyst for NO3− electroreduction.•It exhibits a superior catalytic performances for selective NH3 generation.•It attains a large NH3 yield of 7.9 mg h−1 cm−2 and a Faradaic efficiency of 92.6%.•Zn-NO3− battery with Co2AlO4/CC cathode offers high power densities and NH3 yields.•DFT reveals that Co2AlO4 (220) inhibits HER but shows high NO3− reduction activity.
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 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 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 (ΔG of 0.42 eV) for the potential-determining step (*NO3 to *NO3H), much smaller than that of Co3O4 (220) (ΔG of 0.83 eV).