Selenium‐Deficient FeSe₂/Fe₃O₄ Electrocatalyst for Nitrate Reduction to Ammonia

Electrocatalytic reduction of NO₃ ^- is a green and sustainable method that not only helps to treat industrial pollutants in wastewater, but also produces valuable chemicals. However, the slow dynamics of the proton-coupled electron transfer process results in a high barrier and low conversion efficiency. In this work, the Se-deficient FeSe₂/Fe₃O₄ heterojunction was synthesized, which showed excellent electrochemical performance in 0.1 M nitrate reduction reaction, superior to most currently reported catalysts. The high activity of Se-deficient FeSe₂/Fe₃O₄ is due to the synergistic effect between FeSe₂ and Fe₃O₄ to achieve relay catalytic NO₃ ^- reduction. Among them, the Se-deficient FeSe₂ contributes to NO₃ ^- deoxygenation and subsequent hydrogenation, and Fe₃O₄ promotes H₂O decomposition to provide H proton, jointly promote NO₃RR. Finally, the online differential electrochemical mass spectra (DEMS), in situ Raman and DFT calculation confirmed the optimal pathway for NO₃RR to NH₃ on Se-deficient FeSe₂/Fe₃O₄(100). This strategy of relay catalysis provides a potential way to treat wastewater with high concentration nitrate.