Decoupling Electronic Activation and Pore Connectivity in Acidic Oxygen Reduction on Metal‐Free Biomass‐Derived Carbon Catalysts

Acidic oxygen reduction is often discussed as if catalytic activation and mass transport were inseparable. Here, biomass‐derived carbon was used to examine these contributions through oxidation, ammonia annealing, and KOH activation. The onset potential is associated primarily with defect‐derived p _z / π electronic states, whereas the maximum slope in the transport‐influenced region is associated with hierarchical pore accessibility and connectivity. Apparent electrochemically accessible surface area does not correlate significantly with onset potential in the six‐sample series, although it covaries with maximum slope; this covariance is attributed to pore accessibility rather than surface area itself. Multiscale X‐ray tomography of the optimized catalyst visualizes connected pore pathways from macro‐ to submicrometer scales, while the connected framework may be partly inherited from the rice‐husk precursor. The combined results support preferentially separate consideration of electronic activation and pore‐network accessibility for the acidic oxygen reduction reaction.