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

Abstract

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.