One-step synthesis of TiO2 nanoarrays with basal Rh enrichment for durable ampere-level hydrogen evolution in alkaline seawater.

Abstract

Durable hydrogen evolution in alkaline seawater at high current densities requires electrode architectures that preserve catalytic-site accessibility despite mineral fouling and repeated bubble evolution. To address this accessibility-durability balance, we designed a self-supported Rh/TiO2/Ti electrode with Rh preferentially near the base of the open TiO2 nanoarrays. The open arrays provide pathways for electrolyte access, whereas Rh is positioned away from the outermost array surface. A one-step solvothermal process first forms an Rh-containing layer on Ti and then grows rutile TiO2 arrays in situ, promoting the preferential localization of Rh-containing species near the array base. In seawater containing 1.0 M KOH, the optimized electrode requires an overpotential of 17 mV at 10 mA cm-2. It further sustains 1 A cm-2 for 700 h. Post-electrolysis SEM and XPS show that deposits accumulate mainly in the outer array region, the overall TiO2 nanoarray architecture remains intact, and a pronounced Rh 3d signal remains. These results demonstrate the feasibility of an integrated electrode design combining Rh enrichment near the TiO2 array roots with an electrolyte-accessible nanoarray architecture for sustained ampere-level HER in alkaline seawater.

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