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

Abstract

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 (H_ads ) 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 H_ads 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 H_ads , and meanwhile modulates the electronic structure of Co for strengthened adsorption of H_ads 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.