Hydrogen peroxide (H₂O₂) can be sustainably synthesized through the electrochemical oxygen reduction reaction in a dual-chamber water electrolyzer separated by expensive ion exchange (IX) membranes. The development of an IX membrane-free electrolyzer has been limited by direct anodic degradation of the produced H₂O₂. Here, we devise a bubble shielding strategy by using a low-cost polytetrafluoroethylene hydrophobic porous layer (HPL) on the anode that enables numerous sites for anodically generated oxygen bubbles and significantly suppresses H₂O₂ degradation in the electrolyte. The H₂O₂ production increases by ~600% compared to that using non-bubble shielded anode. A high H₂O₂ concentration of 10.05 ± 0.05 g L⁻¹ at 40 mA cm⁻² can be obtained with both HPL-coated anode and cathode. A solar-driven disinfection device equipped with HPL-coated electrodes achieves >99.9% E. coli inactivation within 60 min. This innovative approach for achieving high electrochemical H₂O₂ concentrations in IX membrane-free electrolyzers more generally provides insights for fine tuning three-phase interfaces and could be applicable to other reactions pathways in electrochemical applications.

https://www.nature.com/articles/s41467-025-57116-x