Dual‐Site W‐O‐CoP Catalysts for Active and Selective Nitrate Conversion to Ammonia in a Broad Concentration Window

Environmentally friendly electrochemical reduction of contaminated nitrate to ammonia (NO3- RR) is a promising solution for large quantity ammonia (NH3 ) production, which, however, is a complex multi-reaction process involving coordination between different reaction intermediates of nitrate reduction and water decomposition-provided active hydrogen (Hads ) species. Here, a dual-site catalyst of [W-O] group-doped CoP nanosheets (0.6W-O-CoP@NF) has been designed to synergistically catalyze the NO3- RR and water decomposition, especially the reactions between the intermediates of NO3- RR and water decomposition-provided Hads species. This catalytic NO3- RR exhibits an extremely high NH3 yield of 80.92 mg h-1 cm-2 and a Faradaic efficiency (FE) of 95.2% in 1 m KOH containing 0.1 m NO3- . Significantly, 0.6W-O-CoP@NF presents greatly enhanced NH3 yield and FE in a wide NO3- concentration ranges of 0.001-0.1 m compared to the reported. The excellent NO3- RR performance is attributed to a synergistic catalytic effect between [W-O] and CoP active sites, in which the doped [W-O] group promotes the water decomposition to supply abundant Hads , and meanwhile modulates the electronic structure of Co for strengthened adsorption of Hads and the hydrogen (H2 ) release prevention, resultantly facilitating the NO3- RR. Finally, a Zn-NO3- battery has been assembled to simultaneously achieve three functions: electricity output, ammonia production, and nitrate treatment in wastewater.