Interrupted Chemical Reaction-based Tri-Phase Design of the FeMoO4/CuFe2S3/CuSe2 Electrocatalyst for Enhancing Electrochemical Nitrogen Reduction

Abstract

Electrochemical nitrogen reduction reaction (N2RR) to ammonia (NH3) is a sustainable and eco-friendly approach that can help restore the disrupted nitrogen cycle and address environmental challenges. However, achieving selective NH3 synthesis is difficult due to the complex nitrogen reduction process, competition from the hydrogen evolution reaction (HER), the strong N≡N triple bond, and the low solubility of N2 in water. Therefore, the design and development of highly efficient N2RR catalysts are crucial for industry and the environment. This study presents a FeMoO4/CuFe2S3/CuSe2 tri-phase system, synthesized by an interrupted reaction, as a highly efficient electrocatalyst for N2RR. The optimized catalyst achieves a remarkable Faradaic Efficiency of 93.8 % and a high ammonia yield rate of 6.15 mg h−1 cm⁻2 or 1229 μg h−1 mgcat⁻1 at −0.6 V vs. RHE. The stack cell, integrating an Fe(MoO4)/CuFe2S3/CuSe2 cathode and a NiFeV anode, delivers an outstanding NH3 yield of 2.09 mg h−1 cm-2 with 50.9% FE at 2.0 V, and low energy consumption of 18.58 kWh/kg. These results not only exceed the performance of most reported transition metal-based catalysts but also surpass the CSIRO benchmark targets for electrochemical ammonia synthesis, underscoring the practical potential and superior catalytic design of this system. The enhanced performance is attributed to the presence of oxygen vacancies and variable oxidation states in the FeMoO4/CuFe2S3/CuSe2 electrocatalyst, which were induced by incorporating selenium and copper into the catalyst system. The trapping of inert N2 is enhanced through oxygen vacancy-mediated polarization, metal-site vacancies, and interfacial effects between catalyst phases. This study presents a versatile approach for designing catalysts that enhance electrocatalytic methods for ammonia (NH3) production through electrochemical nitrogen reduction.