Efficient Ammonia Electrosynthesis and Energy Conversion through a Zn‐Nitrate Battery by Iron Doping Engineered Nickel Phosphide Catalyst

Abstract The electrocatalytic nitrate reduction reaction (NO 3 ‐RR) to ammonia (NH 3 ) offers a promising alternative approach for NH 3 production and nitrate‐based voltaic cells which can deliver both electricity and NH 3 as products, are also highly attractive. However, nitrate‐to‐NH 3 conversion involves a proton‐assisted multiple‐electron transfer process with considerable kinetic barrier, underlying the need for efficient catalysts for the NO 3 – RR. A Zn‐nitrate battery is reported to enable a “killing three birds with one stone” strategy for energy supply, ammonia production and removal of pollutants with the iron doped nickel phosphide (Fe/Ni 2 P) as a NO 3 – RR catalyst electrode. Iron doping induces a downshift of the d‐band center of Ni atoms to the Fermi level, allowing the optimization of Gibbs free energies for reaction intermediates. The Fe/Ni 2 P catalyst exhibits 94.3% NH 3 Faradaic efficiency (FE) and nearly 100% nitrate conversion efficiency at –0.4 V vs. reversible hydrogen electrode (RHE). Further applying this highly efficient NO 3 – RR electrocatalyst as the cathode material, a novel Zn‐nitrate battery exhibits a power density of 3.25 mW cm –2 and a FE of 85.0% for NH 3 production. This work enriches the application of Zn‐based batteries in the field of electrocatalysis and highlights the promise of bimetal phosphide for the NO 3 – RR.