Regulating the d-Band Center of Metal–Organic Frameworks for Efficient Nitrate Reduction Reaction and Zinc-Nitrate Battery

Abstract

The electrochemical reduction of nitrate ions to valuable ammonia enables the recovery of nitrate pollutants from industrial wastewater, thereby synchronously balancing the nitrogen cycle and achieving NH3 production. However, the currently reported electrocatalysts still suffer from the low NH3 yield rate, NH3 Faradaic inefficiency, and NH3 partial current density. Herein, a strategy based on the regulation of the d-band center by Ru doping is presented to boost ammonia production. Theoretical calculations unravel that the Ru dopant in Ni metal–organic framework shifts the d-band center of the neighboring Ni sites upward, optimizing the adsorption strength of the N-intermediates, resulting in greatly enhanced nitrate reduction reaction performance. The synthesized Ru-doped Ni metal–organic framework rod array electrode delivers a NH3 yield rate of 1.31 mmol h–1 cm–2 and NH3 Faradaic efficiency of 91.5% at −0.6 V versus reversible hydrogen electrode, as well as good cycling stability. In view of the multielectron transfer in nitrate reduction and electrocatalytic activity, the Zn-NO3– battery is assembled by this electrode and Zn anode, which delivers a high open-circuit voltage of 1.421 V and the maximum output power density of 4.99 mW cm–2, demonstrating potential application value.