Electrochemical ammonia synthesis via nitrate reduction on perovskite LaxFeO3−δ with enhanced efficiency by oxygen vacancy engineering

Abstract

It is a novel and challenging task to seek an effective electrocatalyst to synthesize valuable ammonia from the harmful nitrate in the wastewater. This work innovatively applied the perovskite La_xFeO_3−δ (x = 1, 0.95, 0.9) as an electrocatalyst to reduce nitrate to ammonia. For the catalyst L_0.9F, the highest NH₃ yield was up to 1024.8 μg h⁻¹ cm⁻² at −1.0 V (vs. RHE), while the maximum faradaic efficiency was 78.1% achieved at −0.8 V (vs. RHE). The outstanding electrocatalytic activities were attributed to the oxygen vacancies generated from the A-site deficiencies. The N–O bonds were weakened with the oxygen atoms in the nitrate filling the oxygen vacancies. The adsorption and transformation of reaction intermediates were promoted due to the existence of oxygen vacancies. Meanwhile, the oxygen vacancies could serve as the active sites of the catalysts, and the deficiencies enhanced the charge transfer efficiency. This work provides a direction to fabricate efficient electrocatalysts for reducing nitrate to ammonia, which can effectively assist in handling both the energy crisis and the environmental pollution.