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

摘要

The electrocatalytic nitrate reduction reaction (NO3-RR) to ammonia (NH3) offers a promising alternative approach for NH3 production and nitrate-based voltaic cells which can deliver both electricity and NH3 as products, are also highly attractive. However, nitrate-to-NH3 conversion involves a proton-assisted multiple-electron transfer process with considerable kinetic barrier, underlying the need for efficient catalysts for the NO3-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/Ni2P) as a NO3-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/Ni2P catalyst exhibits 94.3% NH3 Faradaic efficiency (FE) and nearly 100% nitrate conversion efficiency at -0.4 V vs. reversible hydrogen electrode (RHE). Further applying this highly efficient NO3-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 NH3 production. This work enriches the application of Zn-based batteries in the field of electrocatalysis and highlights the promise of bimetal phosphide for the NO3-RR.