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 O₂ 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.