Supersolidophobic Pt catalyst for long-term natural seawater electrolysis with hydrogen production and magnesium extraction

The electrochemical synthesis of solid compounds is a critical emerging area in electrocatalysis; however, a major challenge is still remaining on severe catalysts scaling driven by strong solid-solid interactions, giving rise to rapid electrode deactivation. In this study, for the example of simultaneous synthesis of Mg(OH)2 and H2 from natural seawater electrolysis, we demonstrate that Pt catalyst with surface-coordinated halogens (F, Cl, Br, I) can alleviate this scaling effect (i.e., solidophobicity) by like-charge repulsion and thus regulating the local environment. Specifically, Pt-I coordination results in supersolidophobicity, achieving a successful extraction of Mg(OH)2 ( > 99% purity) while stably producing H2 (under 100 mA cm-2 for over 5000 hours). A combination of experimental and theoretical studies reveals that, due to the like charge repulsion between I- and in situ generated OH-, the Pt-I catalyst regulates the surface pH gradient which increases the distance from the electrode surface to the Mg(OH)2 nucleus (>4 μm) and facilitates homogeneous nucleation. Additionally, the scalability of the Pt-I catalyst, along with the techno-economic analysis and life cycle assessment of the natural seawater electrolysis technology are systematically demonstrated. Electrochemical synthesis of solid compounds is an emerging frontier in electrocatalysis. Here, the authors report a Pt catalyst whose surface-coordinated halogens alleviate the scaling effect by regulating the local environment and enable simultaneous Mg(OH)₂ and H₂ production from natural seawater.