In Situ Growth of Tungstite (WO3·H2O) on Microporous and Mesoporous Silicas for Enhanced Oxygen-Evolving Photocatalysis

Developing an efficient photocatalytic water-splitting system requires enhancing the intrinsic activities of both the oxygen evolution photocatalyst (OEP) and the hydrogen evolution photocatalyst (HEP). While recent studies have shown that tungstite (WO₃·H₂O) can stably oxidize water to O₂ using a broader spectrum of visible light compared to WO₃, further improvements in its photocatalytic performances as an OEP are needed. One alternative is the use of supported photocatalysts; a uniform suspension of WO₃·H₂O on inert SiO₂ spheres reduces the amount of photocatalysts and provides more active sites. In this work, we report the impregnation of WO₃·H₂O onto the surface of two types of amorphous silica (microporous and mesoporous) in a one-pot synthesis using Pluronic P123 (P123) and Pluronic F127 (F127) templates. Structural characterization revealed that the resulting composites (SiOHW-P123 and SiOHW-F127) are single-phase materials, with WO₃·H₂O nanoparticles anchored to the silica’s surface via hydrogen bonding. Additionally, the conduction band minimum (CBM) of silica-impregnated WO₃·H₂O exhibited a significant positive shift compared to lone tungstite, which could be attributed to the increased tilt angle of W─O─W bonds induced by interactions with the amorphous silica framework. The SiOHW-F127 composite displayed a more uniform dispersion of tungstite across the surface, leading to a higher number of electrocatalytic sites, as confirmed by electrochemical impedance measurements. As a result, both composites demonstrated stable O₂ generation in aqueous Ag⁺ solutions. Precisely, results demonstrate that O₂ production rates over SiOHW-P123 and SiOHW-F127 were two and three times higher, respectively, than over lone WO₃·H₂O. These findings highlight the potential of these composites as promising building blocks for photocatalytic water-splitting systems.