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 CO ₂ emission. An electrochemical method assisted by photoenergy is widely utilized for the chemical energy conversion. In this work, earth-abundant iron pyrite (FeS ₂ ) nanocrystals grown on carbon fiber paper (FeS ₂ /CFP) are found to be an electrochemical and photoactive catalyst for nitrogen reduction reaction under ambient temperature and pressure. The electrochemical results reveal that FeS ₂ /CFP achieves a high Faradaic efficiency (FE) of ≈14.14% and NH ₃ yield rate of ≈0.096 µg min ^-1 at -0.6 V versus RHE electrode in 0.25 m LiClO ₄ . During the electrochemical catalytic reaction, the crystal structure of FeS ₂ /CFP remains in the cubic pyrite phase, as analyzed by in situ X-ray diffraction measurements. With near-infrared laser irradiation (808 nm), the NH ₃ yield rate of the FeS ₂ /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 N ₂ molecule has strong chemical adsorption energy on the iron atom of FeS ₂ . Overall, iron pyrite-based materials have proven to be a potential electrocatalyst with photoactive behavior for ammonia production in practical applications.
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