Hydrogen Spillover Synergistically Enhances Electrocatalytic Nitrate Reduction to Ammonia on SnO ₂ ‐CuO Heterointerfaces

ABSTRACT The electrocatalytic nitrate reduction reaction (NO ₃ RR) offers an ideal solution to addressing nitrogen cycle imbalances and energy challenges. However, the competing hydrogen evolution reaction and limited efficient catalysts result in unsatisfactory NO ₃ RR efficiency. Herein, SnO ₂ ‐CuO hollow nanofibers with hierarchical heterointerfaces were prepared via an electrospinning and calcination strategy. Experimental and theoretical calculations demonstrate that Sn sites in the SnO ₂ ‐CuO hierarchical heterojunction can effectively promote water splitting to provide active hydrogen ( ^* H), while Cu sites facilitate the adsorption and reduction of NO ₃ ⁻ , which accelerates the hydrogenation reaction of ^* NO _x intermediates. Furthermore, charge redistribution at the SnO ₂ ‐CuO interface generates a built‐in electric field, significantly reducing the diffusion energy barrier of ^* H and promoting the migration kinetics of electrons/ ^* H, thereby achieving efficient collaboration between hydrogen spillover and electron transfer at the interface. The as‐prepared SnO ₂ ‐CuO composite achieved superior Faradaic efficiency (94.89%, – 0.9 V vs RHE) and NH ₃ yield (628.14 µmol h ⁻¹ cm ⁻² ). A rechargeable Zn‐NO ₃ ^– battery fabricated using this catalyst continuously produces NH ₃ while discharging electrical energy, highlighting the feasibility of an integrated platform for pollutant resource recovery and energy storage. This study provides effective insights into the advanced structural and functional design of highly efficient NO ₃ RR catalysts.