Electrochemical nitrogen reduction to ammonia using mesoporous iron oxide with abundant oxygen vacancies

Abstract

The electrochemical nitrogen reduction reaction (NRR) has emerged as an environmentally benign and sustainable approach for ammonia (NH₃) synthesis. For the development of an efficient NRR electrocatalyst, herein, mesoporous hematite (meso-α-Fe₂O₃) with abundant oxygen vacancies was prepared using a nanocasting method. The synthesized meso-α-Fe₂O₃ exhibited high NRR activity, with an NH₃ yield of 15.3 μg h⁻¹ mg_cat⁻¹ and a faradaic efficiency of 13.2% at −0.15 V versus RHE, corresponding to an overpotential as low as 242 mV. These performances are comparable or even superior to those of most iron-based NRR electrocatalysts. Based on a combination of experiments and density functional theory calculations, the enhanced catalytic activity was attributed to the highly contained oxygen vacancies that served as active sites which favorably adsorb nitrogen molecules, leading to high NRR selectivity.