Ferromagnetic Ordering Outperforms Coordination Effects in Governing Oxygen Reduction Catalysis on High‐Index Nickel Single Crystals

Abstract The role of surface spin configuration in spin‐dependent catalytic reactions remains contentious, particularly when compared to the established dominance of coordination environments. Here, we resolve this debate by systematically probing oxygen reduction reaction (ORR) mechanisms on high‐index Ni single‐crystal facets ([210], [310], [520]) through integrated density functional theory (DFT) and experimental studies. Contrary to conventional d‐band center predictions, we demonstrate that ferromagnetic ordering fundamentally dictates catalytic activity by stabilizing triplet O 2 adsorption and lowering spin‐forbidden transition barriers. The Ni (210) facet exhibits superior ORR performance (half‐wave potential: 0.842 V vs. RHE), outperforming Ni (310) and Ni (520) due to its optimized d‐band center and enhanced saturation magnetization. External magnetic fields amplify this effect, yielding a 28% current density enhancement for Ni (210)—nearly triple that of Ni (520). Spin‐polarized DFT calculations reveal that ferromagnetic ordering reduces the potential‐determining step energy barrier for *OH desorption by 7.0%, overriding coordination‐number effects. These findings establish ferromagnetic alignment as a critical design criterion for spin‐engineered electrocatalysts, offering a paradigm shift from coordination‐centric optimization to spin‐polarized interface engineering.