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.