Location and State of Pt in Platinized CdS/TiO₂ Photocatalysts for Hydrogen Production from Water under Visible Light

CdS/TiO 2 composite photocatalysts were platinized by different methods such as photodeposition (PD), wet impregnation (WI), and chemical reduction (CR), and studied for hydrogen production from water under visible light. All Pt species were in the metallic state, yet PD and WI photocatalysts contained electron-deficient Pt. In particular, Pt−Ti formation was identified in the WI catalyst, which contributed to electron deficiency of Pt. These two photocatalysts of electron-deficient Pt exhibited higher rates of hydrogen evolution due to favorable diffusion of photoelectrons from excited CdS toward the Pt. Between PD and WI photocatalysts, the PD catalyst showed a lower rate because part of the Pt in the catalyst resided on CdS, whereas all Pt species were located on TiO 2 nanoparticles for WI and CR catalysts. The results indicate that the location as well as the electronic state of Pt is important for the high performance of platinized CdS/TiO 2 photocatalysts in hydrogen production from water.