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.