Photoactive Earth-Abundant Iron Pyrite Catalysts for Electrocatalytic Nitrogen Reduction Reaction

The generation of ammonia, hydrogen production, and nitrogen purification are considered as energy intensive processes accompanied with large amounts of CO₂ emission. An electrochemical method assisted by photoenergy is widely utilized for the chemical energy conversion. In this work, earth-abundant iron pyrite (FeS₂ ) nanocrystals grown on carbon fiber paper (FeS₂ /CFP) are found to be an electrochemical and photoactive catalyst for nitrogen reduction reaction under ambient temperature and pressure. The electrochemical results reveal that FeS₂ /CFP achieves a high Faradaic efficiency (FE) of ≈14.14% and NH₃ yield rate of ≈0.096 µg min^-1 at -0.6 V versus RHE electrode in 0.25 m LiClO₄ . During the electrochemical catalytic reaction, the crystal structure of FeS₂ /CFP remains in the cubic pyrite phase, as analyzed by in situ X-ray diffraction measurements. With near-infrared laser irradiation (808 nm), the NH₃ yield rate of the FeS₂ /CFP catalyst can be slightly improved to 0.1 µg min^-1 with high FE of 14.57%. Furthermore, density functional theory calculations demonstrate that the N₂ molecule has strong chemical adsorption energy on the iron atom of FeS₂ . Overall, iron pyrite-based materials have proven to be a potential electrocatalyst with photoactive behavior for ammonia production in practical applications.