Integrating Spin‐Promotion Effect With Accelerated Proton‐Coupled Electron Transfer in Nanoreactor for Enhanced Oxygen Electroreduction

Single‐atom catalysts maximize atomic utilization for the oxygen reduction reaction (ORR), yet their performance is hindered by sluggish proton‐coupled electron transfer (PCET) processes and inefficient mass transport. To overcome these limitations, we design a mesopore‐dominant sulfur‐doped iron single‐atom carbon nanoreactor (Fe/S‐SACNR), which synergistically optimizes the atomic coordination environment and hierarchical porosity. The Fe single atoms, anchored in a Fe 1 N 4 S 1 configuration, exhibit tailored electronic asymmetry that fine‐tunes oxygen intermediate adsorption and accelerates ORR kinetics. Combined with a cellular‐inspired mesoporous framework, Fe/S‐SACNR ensures exceptional mass transport, mesochannel confinement effects locally enrich oxygen concentration, and near‐complete active‐site accessibility (97.2%, density: 7.27 × 10 20 sites g −1 ). Density functional theory and in situ spectroscopy reveal the critical role of S‐coordination in modulating the Fe spin state to optimize *OH desorption and promote PCET during ORR. The Fe/S‐SACNR achieves a half‐wave potential of 0.925 V in alkaline media and drives zinc‐air batteries to a peak power density of 334.09 mW cm −2 with ultralong stability (>1000 h). Furthermore, an ampere‐hour‐scale battery (2.6 Ah capacity) operates stably for >48 h at 0.5 A, highlighting practical viability. This work demonstrates a dual‐regulation strategy—bridging atomic‐scale electronic engineering and mesoscopic structural design—to advance high‐performance ORR catalysts for energy applications.