Cu1-Fe Dual Sites for Superior Neutral Ammonia Electrosynthesis from Nitrate

Abstract

The electrochemical nitrate reduction reaction (NO₃RR) is able to convert nitrate (NO₃ ^-) into reusable ammonia (NH₃), offering a green treatment and resource utilization strategy of nitrate wastewater and ammonia synthesis. The conversion of NO₃ ^- to NH₃ undergoes water dissociation to generate active hydrogen atoms and nitrogen-containing intermediates hydrogenation tandemly. The two relay processes compete for the same active sites, especially under pH-neutral condition, resulting in the suboptimal efficiency and selectivity in the electrosynthesis of NH₃ from NO₃ ^-. Herein, we constructed a Cu₁-Fe dual-site catalyst by anchoring Cu single atoms on amorphous iron oxide shell of nanoscale zero-valent iron (nZVI) for the electrochemical NO₃RR, achieving an impressive NO₃ ^- removal efficiency of 94.8 % and NH₃ selectivity of 99.2 % under neutral pH and nitrate concentration of 50 mg L^-1 NO₃ ^--N conditions, greatly surpassing the performance of nZVI counterpart. This superior performance can be attributed to the synergistic effect of enhanced NO₃ ^- adsorption on Fe sites and strengthened water activation on single-atom Cu sites, decreasing the energy barrier for the rate-determining step of *NO-to-*NOH. This work develops a novel strategy of fabricating dual-site catalysts to enhance the electrosynthesis of NH₃ from NO₃ ^-, and presents an environmentally sustainable approach for neutral nitrate wastewater treatment.

Keywords: Ammonia Recovery; Dual sites; Nitrate Electroreduction; Nitrate-pollution Treatment; Single Atom Copper.