Electrochemically synthesized SnO2 with tunable oxygen vacancies for efficient electrocatalytic nitrogen fixation

Abstract

Electrochemical nitrogen reduction reaction (NRR) driven by a renewable energy source offers a sustainable and environmentally benign route to produce ammonia (NH₃), but it is highly dependent on efficient and specific catalysts to reduce the high reaction barrier and improve the selectivity. Defect engineering is extensively used to regulate the surface properties of materials to improve their catalytic performance. Herein we synthesized SnO₂ with different oxygen vacancy concentrations by a controllable electrochemical method for electrocatalytic nitrogen (N₂) fixation. The prepared SnO₂ was used as an electrocatalyst and exhibited excellent NRR performance with an optimal NH₃ yield rate of 25.27 μg h⁻¹ mg_cat.⁻¹ and faradaic efficiency of 11.48% at −0.6 V (vs. the reversible hydrogen electrode) in 0.1 M Na₂SO₄. Oxygen vacancies provide more active sites and greater electron transfer ability on the catalyst surface to facilitate N₂ adsorption and activation. The electrocatalytic NRR performance of SnO₂ was enhanced with the increase in oxygen vacancy concentration. The density functional theory calculations indicate that the oxygen vacancies in SnO₂ promote the electrocatalytic NRR performance by increasing the number of valence electrons of Sn and decreasing the energy barrier of the potential-determining step, thus promoting the activation of the N–N bond to further achieve efficient N₂ fixation.