Boosting TiO2 photocatalytic hydrogen production via silica-core engineering, optimized shell architecture, and Pd nanoparticles decoration

Photocatalytic wastewater photoreforming is recognized as a sustainable method for hydrogen generation. In this study, a SiO 2 @TiO 2 –Pd photocatalyst was rationally designed to achieve a balance among high photocatalytic efficiency, ease of recovery, and recyclability. This work also addresses unexplored factors, including the role of the SiO 2 core in H 2 evolution and the influence of the TiO 2 shell thickness on photocatalytic performance. To this end, several core@shell SiO 2 @TiO 2 photocatalysts with controlled TiO 2 shell thicknesses were synthesized. The experiments on H 2 evolution from glycerol photoreforming revealed that the hydrogen evolution rate is strongly influenced by both the TiO 2 shell thickness and the SiO 2 core, with the optimum TiO 2 shell thickness (ca. 28 nm) photocatalyst showing a hydrogen generation rate 7 times higher than that of P25 (based on HER rates normalized to the photoactive component of the materials). Decoration of the surface of the optimized SiO 2 @TiO 2 photocatalyst with Pd nanoparticles further increased the hydrogen production rate per photoactive gram by 54-fold (31.9 mmol·h −1 ·g −1 ). To understand the mechanisms underlying the improved photocatalytic performance, photophysical and (photo)electrochemical characterizations were performed using laser flash photolysis, photoluminescence spectroscopy, and photocurrent measurements. Overall, this study demonstrates that a SiO 2 core not only facilitates easier photocatalyst recovery but also positively influences its H 2 production performance, resulting in a material 371 times more active than P25. These findings pave the way for the development of SiO 2 -supported photocatalysts for simultaneous treatment of wastewater and hydrogen production in continuous-flow systems.