Scalable and hardness-tolerant H2O2 electrosynthesis in tap-water-based electrolytes enabled by electrode architecture and reactor engineering

Electrochemical synthesis of hydrogen peroxide (H 2 O 2 ) presents a sustainable paradigm for decentralized chemical manufacturing, yet its practical implementation is severely impeded by catastrophic scaling in tap water electrolytes. Here, we reveal that on conventional gas diffusion electrodes, localized alkalinity-induced scaling precipitates a fatal hydrophilic transition, triggering irreversible water flooding and failure. To circumvent this, we introduce a structurally discontinuous electrode architecture engineered with artificial micro-cracks, which demonstrates exceptional stability for over 800 h at 100 mA cm −2 in tap-water-based electrolytes while maintaining a Faradaic efficiency >80 %. Operando electrochemical reflection-absorption imaging elucidates a unique tolerance mechanism wherein the crack channels retain their hydrophobicity and gas permeability to support sustained reaction despite the severe deactivation of catalyst islands by scaling. Leveraging this design, we engineer a scaled-up, membrane-free electrolyzer that, operating directly with tap water at 100 mA cm −2 , achieves high-throughput H 2 O 2 production (600 mL min −1 ) for >200 h. This work resolves the critical hardness tolerance bottleneck, establishing a robust foundation for the deployment of on-site H 2 O 2 electrosynthesis in diverse real-world water matrices.