Electrocatalytic fixation of N2 into NO3−: electron transfer between oxygen vacancies and loaded Au in Nb2O5−x nanobelts to promote ambient nitrogen oxidation

Abstract

The electrocatalytic nitrogen oxidation reaction (NOR) is a promising alternative to the industrial synthesis of nitrate. However, with the enhancement of NOR activity by modification methods, the competitive oxygen evolution reaction (OER) is always improved simultaneously. Here, a hybrid electrocatalyst composed of Au nanoparticles and oxygen vacancy-enriched niobium oxide nanobelts (Au–Nb₂O_5−x) was prepared on niobium foil for N₂ fixation into NO₃⁻. The results of X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) demonstrate that electron transfer occurs between Au nanoparticles and the oxygen vacancies in Nb₂O_5−x nanobelts, which adjusts the electronic structures of oxygen vacancies near the Au/Nb₂O_5−x interface. Electrochemical and N₂ temperature-programmed desorption (TPD) tests indicate that the optimization of the electronic structure suppresses the activity of the competitive OER on oxygen vacancy sites and facilitates nitrogen adsorption on the surface of Au–Nb₂O_5−x, which significantly enhances the NOR performance of the electrocatalyst.