Carbon Fiber‐Induced Crack Control and Polymethylhydrosiloxane‐Modified Naturally Aspirated Gas Diffusion Electrode for High‐Throughput H ₂ O ₂ Electrosynthesis

ABSTRACT Electrochemical H 2 O 2 production via the two‐electron oxygen reduction reaction (2e − ‐ORR) offers green, distributed synthesis, yet gas diffusion electrodes (GDEs) degrade at industrial current densities since electrowetting collapses the three‐phase interface and restricts O 2 delivery. Herein, a modified naturally aspirated cathode (MNAC) couples a carbon‐fiber‐induced through‐thickness crack network that creates multipath gas channels with in situ polymethylhydrosiloxane (PMHS) treatment that renders crack walls and the carbon matrix superhydrophobic, sustaining an oxygen‐accessible boundary under high load. MNAC delivers an oxygen diffusion coefficient of 1.25 × 10 −5 m 2 s −1 , approaching the molecular diffusivity of O 2 in air (2 × 10 −5 m 2 s −1 ), and an oxygen utilization efficiency of 52.2% without external aeration. This near‐air‐limit transport ranks among the highest values reported for aeration‐free carbonaceous GDE cathodes. MNAC sustains 100 mA cm −2 for 100 h, producing 60.66 mg h −1 cm −2 H 2 O 2 with current efficiency above 88%. A H 2 O 2 productivity of 141.0 mg h −1 cm −2 is achieved at 250 mA cm −2 , supporting high‐throughput H 2 O 2 electrosynthesis. Density functional theory links the enhanced selectivity to PMHS‐driven reorganization of the carbon/PTFE interphase that stabilizes *OOH and increases the thermodynamic penalty for O─O bond scission. This work provides a scalable, self‐feeding carbon GDE platform for high‐throughput H 2 O 2 electrosynthesis.