Impact of Pt loading methods over mesoporous-assembled TiO2–ZrO2 mixed oxide nanocrystal on photocatalytic dye-sensitized H2 production activity

Graphical abstract: The Pt loading on the synthesized mesoporous-assembled 0.95TiO2–0.05ZrO2 mixed oxide nanocrystal photocatalyst was comparatively investigated by two methods: single-step sol–gel (SSSG) and photochemical deposition (PCD). The Pt loading by the PCD method was found to be superior to that by the SSSG method in enhancing photocatalytic sensitized hydrogen production under visible light irradiation. The Pt loading amount and PCD conditions, i.e. light irradiation time and light intensity, also had a strong effect on the photocatalytic hydrogen production activity. Highlights: ► Pt-loaded mesoporous-assembled 0.95TiO2–0.05ZrO2 nanocrystals were synthesized. ► Pt loading was performed by single-step sol–gel and photochemical deposition. ► Pt loading by photochemical deposition more enhanced photocatalytic H2 production. ► Pt loading amount and photochemical deposition conditions were optimized. -- Abstract: In this work, the photocatalytic water splitting under visible light irradiation for hydrogen production was investigated by using Eosin Y-sensitized Pt-loaded mesoporous-assembled TiO2–ZrO2 mixed oxide nanocrystal photocatalysts. The mesoporous-assembled TiO2–ZrO2 mixed oxide with the TiO2-to-ZrO2 molar ratio of 95:5 (i.e. 0.95TiO2–0.05ZrO2) was synthesized by using a sol–gel process with the aid of a structure-directing surfactant. The Pt loading was comparatively performed via two different effective methods: single-step sol–gel (SSSG) and photochemical deposition (PCD). The synthesized photocatalysts were methodically characterized by N2 adsorption–desorption, XRD, UV–visible spectroscopy, SEM–EDX, TEM–EDX, TPR, and H2 chemisorption analyses. The results revealed that the Pt loading by the PCD method greatly enhanced the photocatalytic hydrogen production activity of the synthesized mesoporous-assembled 0.95TiO2–0.05ZrO2 mixed oxide photocatalyst more than that by the SSSG method. The optimum Pt loading by the PCD method was experimentally observed at 0.5 wt.%, which was well associated with the maximum Pt dispersion. In addition, the PCD conditions, i.e. UV light irradiation time and UV light intensity, were investigated and optimized to be 2 h and 44 W, respectively.