Gradient-Wettability Oxide-Pt/C Electrocatalysts for Stable Seawater Hydrogen Evolution via Superaerophobicity and Surface Acidity

This study reports the successful development of a series of surface gradient wettability electrocatalysts, Pt₅/C/oxide-50, by integrating hydrophilic oxides (SiO₂, Al₂O₃, CeO₂, and TiO₂) with hydrophobic carbon-supported Pt (Pt/C) without the need for sophisticated surface microstructuring. The hybrid composites exhibited exceptional superaerophobicity, which facilitated the rapid detachment of H₂ bubbles from the Pt active sites, effectively preventing blockage, as confirmed by the H₂ oxidation signals in cyclic voltammograms and water droplet contact-angle measurements. Unlike conventional Pt/C, which suffers from alkaline poisoning during seawater electrolysis, Pt₅/C/oxide-50 mitigates this issue by introducing surface acidic sites via oxides. Linear sweep voltammetry was employed to specifically monitor the oxidation signal associated with OH⁻ adsorption on Pt (Pt-OH -ad) during the hydrogen evolution reaction (HER), revealing that the incorporation of oxides effectively suppresses the formation of Pt-OH ^-_ad. This work demonstrates a facile and scalable approach that combines microwettability modulation with surface acid site engineering to enhance both the durability of the HER and the gas-repelling performance, enabling efficient direct seawater splitting for H₂ production.