Dual–Spillover Mediated Highly Efficient Electrocatalytic Nitrate Reduction to Ammonia Over Co–Doped Sr ₂ CuWO ₆ Double Perovskite

ABSTRACT Electrocatalytic nitrate reduction reaction (NO 3 RR) provides a green route to concurrently mitigate nitrate pollution and address the unsustainability of Haber–Bosch ammonia (NH 3 ) synthesis. However, the development of high–performance NO 3 RR catalysts is plagued by inappropriate active site spacing, insufficient functional synergy, and sluggish multi–proton–coupled multi–electron transfer kinetics. Herein, we design Co–doped Sr 2 CuWO 6 double perovskite catalysts to optimize active site spacing and construct functionally complementary active sites for efficient NO 3 RR. Experimental and theoretical results reveal a synergistic dual–spillover mechanism: the dominant NO 3 − adsorption and initial activation (NO 3 − →NO 2 − ) on Cu sites are promoted by active hydrogen ( * H) from water dissociation on Co sites via hydrogen spillover, whereas the generated * NO 2 intermediates from Cu sites diffuse to Co sites via intermediate spillover for further hydrogenation to NH 3 due to the enhanced * NO 2 adsorption on Co sites. As expected, the optimal Sr 2 Cu 0.7 Co 0.3 WO 6 achieves an exceptional NH 3 yield rate of 47.2 mg h − 1 mg cat −1 with a Faradaic efficiency (FE) of 93 % at −0.7 V (vs. RHE). This work establishes a rational cation doping strategy for constructing functionally complementary active sites in double perovskites, shedding light on the structure–activity relationship and guiding the design of advanced NO 3 RR catalysts for sustainable NH 3 synthesis and nitrate remediation.