Spin‐Matching Effect Triggering Enhanced Oxygen Reduction Reaction in Acidic and Alkaline Media

Abstract The development of high‐performance oxygen reduction reaction (ORR) electrocatalysts operable across broad pH ranges is hindered by strong adsorption of hydroxyl intermediates (*OH). This work introduces a conceptually novel strategy of spin‐state modulation via interfacial engineering to regulate platinum nanocrystals anchored on atomically dispersed Fe‐N‐C substrates (Pt/Fe SA ‐NC). Based on density functional theory (DFT) predictions, we construct a spin‐state‐tunable architecture by precisely controlling Pt particle size (2–8 nm), which induces spin‐matching effects that effectively mitigate *OH over‐binding in pH‐dependent ORR path. Mechanistic studies indicate that the synergy between FeN 4 ‐mediated metal‐support interactions and size‐dependent spin polarization facilitates charge transfer, weakening *OH adsorption and promoting its desorption. In alkaline conditions, ∼2 nm Pt nanoclusters with moderate spin density achieve a peak power density of 179 mW cm −2 in Zn‐air batteries with 150 h stability. Under acidic media, ∼8 nm Pt nanoparticles with low‐spin configuration deliver a mass activity of 0.65 A mg Pt −1 and a peak power density of 730 mW cm −2 in proton‐exchange membrane fuel cells (PEMFCs), outperforming commercial Pt/C and retaining 90% activity after 3000 cycles. This finding provides a spin‐engineering paradigm for designing advanced electrocatalysts with ultralow Pt loading.