The Synergistic Catalysis Effect on Electrochemical Nitrate Reduction at the Dual−function Active Sites of Heterostructure

Advanced design concept of catalysts to drive the efficient electrochemical nitrate reduction reaction (NITRR) is highly desirable for converting the harmful nitrate (NO3-) to ammonia (NH3) as a hydrogen carrier. Herein, the string bead-like nanowire heterostructure derived from the Cu foam electrode (o-CoP/C@Cu3P/CF) is designed to incorporate the advantages of dual-function active sites in the processes of water-splitting and nitrate reduction. In such heterostructures, the theoretical and experimental results confirm that the CoP sites function to accelerate water-splitting to release protons. Furthermore, the Cu3P sites exhibit thermodynamic advantages during adsorption, deoxygenation, and hydrogenation steps of adsorbed intermediates (*NOx). Attributed to the synergistic catalysis effect of the heterostructure, the self-supporting electrode displays an excellent NH3 yield of 1.571 +/- 0.046 mmol h-1 cm-2 at a low potential of -0.25 V vs. RHE in 1 M KOH containing of 100 mM NO3-. As the NO3- concentration decreases to 50 mM and 20 mM, the NH3-faradaic efficiency reached 96.23 +/- 0.55% and 97.02 +/- 1.64%, respectively. Thus, aqueous zinc-nitrate batteries could achieve three goals with one action for nitrate removal, ammonia synthesis, and electricity supply. The synergistic catalysis effect based on CoP and Cu3P dual-function active sites is proposed to understand the mechanism of active hydrogen (*H) and adsorbed intermediates (*NOx) during water-splitting and nitrate reduction.