Constructing an OH−-enriched microenvironment on the electrode surface for natural seawater electrolysis
Jiaxin Guo, Ruguang Wang, Quanlu Wang, Ruize Ma, Jisi Li, Erling Zhao, Jieqiong Shan, Tao Ling
Abstract
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.