Constructing an OH−-enriched microenvironment on the electrode surface for natural seawater electrolysis

Powered by clean energy, the hydrogen fuel production from seawater electrolysis is a sustainable green hydrogen technology, however, chlorine corrosion and correlative oxidation reactions severely erode the catalysts. Our previous work demonstrates that direct seawater electrolysis without a desalination process and strong alkali addition can be realized by introducing a hard Lewis acid oxide on the catalyst surface to capture OH−. However, the criteria for selecting Lewis acid oxides and the origin of OH− enrichment in chlorine chemistry inhibition on the catalyst surface remain unexplored. Here, we compare the ability of a series of Lewis acid oxides with different acidity constants (pKa), including MnO2, Fe2O3, and Cr2O3, to enrich OH− on the Co3O4 anode catalyst surface. Comprehensive analyses suggest that the lower pKa value of the Lewis acid oxide, the higher concentration of OH− enriched on Co3O4 surface, and the lower Cl− concentration. As established correlation among pKa of Lewis acid oxide, OH− enrichment and Cl− repulsion provide direct guidance for future design of highly active, selective and durable catalysts for natural seawater electrolysis.