Tandem Catalysis Driven by Nitrogen Spillover in a Core–Shell Heterostructure for Direct Ammonia Fuel Cells

ABSTRACT Low‐temperature direct ammonia fuel cells (DAFCs) are promising yet challenged by slow ammonia oxidation reaction (AOR) kinetics and severe catalyst poisoning. To address such bottlenecks, we design a vertically aligned NiCo ₂ O ₄ @NiCo ₂ S ₄ core–shell heterostructure where the NiCo ₂ S ₄ shell stands for NH ₃ activization and the NiCo ₂ O ₄ core serves for N ₂ generation. The built‐in electric field at the heterointerface, together with the bimetallic synergy introduced by Ni doping, enables the optimization of electron configuration via work function engineering. Driven by the adsorption energy gradient across heterointerface, the efficient *N spillover promotes the regeneration of NH ₃ adsorption sites and facilitates the efficient desorption of N ₂ , leading to a refined tandem catalytic pathway of NH ₃ ‐*N‐N ₂ . Consequently, NiCo ₂ O ₄ @NiCo ₂ S ₄ achieves a high current density of 972 mA cm ⁻² at 80 °C in a three‐electrode system and delivers 20‐h stability, offering a novel strategy for high‐performance, poison‐tolerant AOR anodes.