Hydrogen production from seawater splitting enabled by on-line flow-electrode capacitive deionization

The conventional method of hydrogen production relies on non-renewable fossil fuels, which conflicts with the objective of future renewable and sustainable energy system. Seawater splitting for hydrogen production using offshore wind/solar power shows much promise as the solution for hydrogen-based energy systems coupling renewable energy. Direct seawater splitting is currently not feasible at a large scale due to its unsatisfactory durability caused by the anodic chloride corrosion which will make the catalyst deactivated and the substrate disintegrated. To tackle the anodic corrosion issue, here we present a novel seawater electrolysis system integrating an on-line flow-electrode capacitive deionization unit with a robust alkaline water electrolyzer. At an operating voltage of 1.6 V, the on-line deionization unit reaches a desalting ratio of 98.47%, so that the detrimental hypochlorite evolution could be greatly suppressed. Combined with a corrosion-resistant anode material—S-NiFeOOH@Ni foam, the connected electrolysis system achieves durable operation for 100 h at industrial-level current density (500 mA cm−2) with the anodic overpotential only at 296 mV. This novel system provides a practical solution for large-scale seawater splitting.