Doping-Engineered Fe-Co Tandem Sites Balance Hydrogen and Nitrite Intermediates for Efficient Nitrate to Ammonia
Abdulla Eziz1, Abulikemu Abulizi1, Changhai Liang2
1Xinjiang Key Laboratory of Coal Clean Conversion & Chemical Engineering, School of Chemical Engineering, Xinjiang University, Urumqi, China.
None:
Electrocatalytic nitrate reduction (NO3 -RR) offers a promising route for simultaneous nitrate remediation and sustainable ammonia (NH3) synthesis. However, its efficiency is limited by low NH3 selectivity, insufficient Faradaic efficiency (FE), and high overpotential, primarily due to inadequate active hydrogen (*H) supply and nitrite (NO2-) accumulation. Herein, we report an Fe─Co tandem catalyst (FeCo/C-0.5) with an optimized Fe/Co ratio that achieves 98% NH3 selectivity and 89.68% FE at -0.33 V vs. RHE, with a yield of 14.12 mg h-1 mgcat -1. Combining in situ FTIR, Raman, DEMS, and DFT calculations, we demonstrate that Fe─Co synergy accelerates H2O dissociation and establishes a dynamic *H balance, suppressing the hydrogen evolution reaction (HER) while maintaining adequate *H supply for hydrogenation. Furthermore, NO2 - generated at Fe sites is rapidly reduced to NH3 at adjacent Co sites, thereby eliminating NO2 - accumulation and enabling high NH3 selectivity at low potentials. The catalyst also demonstrates robust stability in simulated wastewater containing Cl- and SO4 2-, and achieves a power density of 6.63 mW cm-2 in a Zn-NO3 - battery, which underscores its practical potential.
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