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 1st and 2nd 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 3rd 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.