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

Abstract

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.

Keywords: density functional theory; earth-abundant electrocatalysts; in situ XRD measurements; iron pyrite; nitrogen reduction reaction.