Design of a novel CuNi-MOF-based catalyst for efficient electrocatalytic conversion of nitrate to ammonia at low overpotential†

Abstract

The catalytic conversion of nitrate (NO₃⁻) to ammonia (NH₃) has gained significant attention as a promising route for sustainable nitrogen recycling and ammonia production. However, the overall kinetic rate of the NO₃RR is plagued by the complex proton-assisted multiple-electron transfer process. Herein, the CuNi-TBC-C catalyst was designed to optimize the kinetic rate of the NO₃RR. Electrochemical evaluation, in situ FTIR spectra, and kinetic studies demonstrate that Ni enhances the catalytic activity and kinetic rate of Cu-based catalysts for the NO₃RR by modulating the Cu d-orbital center, enhancing the adsorption energy of nitrate, and optimizing the reaction pathway. Thus, the CuNi-TBC-C catalyst efficiently converts NO₃⁻ to NH₃ with a high faradaic efficiency (FE) of 94.68% and a high NH₃ yield rate of 214 μmol h⁻¹ cm⁻² in 1 M KOH and 0.1 M KNO₃ solution at −0.1 V vs. RHE. Furthermore, when applied as the cathode material in a novel Zn-nitrate battery, this highly efficient NO₃RR electrocatalyst achieves a power density of 3.94 mW cm⁻² and an FE of 89.3% for NH₃ production.