Calcium-tolerant electrode strategy for efficient hydrogen peroxide electrosynthesis in natural water

Calcium scaling is traditionally regarded as a major impediment to the practical application of decentralized H 2 O 2 electrosynthesis via two-electron oxygen reduction reaction (2e − ORR). Herein, we demonstrate that the calcium scale unexpectedly enhances H 2 O 2 electroproduction. Dissolved Ca 2+ , rather than precipitated scale, is the dominant factor suppressing H 2 O 2 electrosynthesis. Interfacial enrichment of Ca 2+ facilitates water dissociation and proton accessibility, shifting the pathway toward 4e − ORR. To address this challenge, a quaternary ammonium cationic surfactant-modified cathode is developed, demonstrating a 2.3-fold enhancement in H 2 O 2 yield. Theoretical calculations suggest that surfactant modification weakens Ca 2+ adsorption and reduces its interfacial accumulation through enhanced electrostatic repulsion. Simultaneously, hydrophobic side-chain grafting decreases proton accessibility by disrupting the interfacial hydrogen-bond network, thereby improving 2e − ORR selectivity. Furthermore, a 3D polyurethane sponge-fenced cathode architecture establishes an alkaline microenvironment via pore confinement, mitigating the Ca 2+ -enhanced proton accessibility and increasing H 2 O 2 electroproduction by 293.3%. These strategies of interfacial field manipulation and 3D alkaline confinement provide a promising paradigm for designing Ca 2+ -tolerant cathode for efficient H 2 O 2 electrosynthesis.