Spin polarized Fe₁-Ti pairs for highly efficient electroreduction nitrate to ammonia

Electrochemical nitrate reduction to ammonia offers an attractive solution to environmental sustainability and clean energy production but suffers fromthe sluggish *NO hydrogenation with the spin-state transitions. Herein, we report that the manipulation of oxygen vacancies can contrive spin-polarized Fe-1-Ti pairs on monolithic titanium electrode that exhibits an attractive NH3 yield rate of 272,000 mu gh(-1) mg(Fe)(-1) and a high NH3 Faradic efficiency of 95.2% at -0.4 V vs. RHE, far superior to the counterpart with spin-depressed Fe-1-Ti pairs (51000 mu gh(-1) mg(Fe)(-1)) and the mostly reported electrocatalysts. The unpaired spin electrons of Fe and Ti atoms can effectively interact with the key intermediates, facilitating the *NO hydrogenation. Coupling a flow-through electrolyzer with a membrane-based NH3 recovery unit, the simultaneous nitrate reduction and NH3 recovery was realized. This work offers a pioneering strategy formanipulating spin polarization of electrocatalysts within pair sites for nitrate wastewater treatment.