Electrochemical Reduction of Nitrate to Ammonia on an In Situ-Derived Co3O4@CoBi Core–Shell Nanoarray

Room-temperature nitrate electroreduction can simultaneously synthesize ammonia and eliminate N-contaminants, which has attracted a lot of interest but still needs efficient electrocatalysts. Here, we report the in situ derivation of an amorphous cobalt borate (CoBi) film on a Co3O4 nanoarray on carbon cloth (Co3O4@CoBi/CC) for efficient ammonia generation via selective electroreduction of nitrate at room temperature and atmospheric pressure. In a neutral phosphate-buffered electrolyte containing 0.1 M NaNO3, such a catalyst exhibits a maximum ammonia yield rate of 6.80 mg/h/cm2 (−1.0 V vs RHE) and a high Faradaic efficiency of up to 97% (−0.7 V vs RHE). Besides, its catalytic activity remains stable in recycling tests and long-term electrolysis. An aqueous Zn nitrate battery with Co3O4@CoBi/CC as the cathode shows a high battery performance as well.