Spin polarized Fe 1 -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 from the 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 NH 3 yield rate of 272,000 μg h -1 mg Fe -1 and a high NH 3 Faradic efficiency of 95.2% at -0.4 V vs. RHE, far superior to the counterpart with spin-depressed Fe 1 -Ti pairs (51000 μg h -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 NH 3 recovery unit, the simultaneous nitrate reduction and NH 3 recovery was realized. This work offers a pioneering strategy for manipulating spin polarization of electrocatalysts within pair sites for nitrate wastewater treatment.