A triple-defense electrocatalyst for robust seawater oxidation

While coastal renewable energy-powered seawater electrolysis is highly promising for green H₂ production, the anodic chemical corrosion by aggressive chlorine chemistry and violent bubble release-induced physical damage to anodes are two long-standing issues that lead to inferior stability. Here we pursue integrating triple protection to a monolithic catalyst to concurrently alleviate chlorine chemistry and weaken external forces from bubble escaping/collapsing. The 1^st and 2^nd defenses are a Co-phosphate (Co-Pi) outer layer closely connected to CoP and well-dispersed nanosized γ-MnO₂ in/on Co-Pi, which collectively and preferentially filter out chloride ions approaching the catalytic sites based on their semipermeable natures. The 3^rd defense comes from structural features that specialize in lessening the forces of bubble movements on the catalyst. A cage-shaped array composed of tip-connected nanowires with rough surfaces is verified to possess enhanced mechanical stability by theoretical simulations and experiments. This triple-protected electrocatalyst achieves a 3000-h electrolysis lifespan in real seawater during the ampere-level current density operation, demonstrating a multi-defense electrode design with guiding significance for wide applications.