Enhancement of Photocatalytic Activity for Hydrogen Production by Surface Modification of Pt-TiO2 Nanoparticles with a Double Layer of Photosensitizers.

To investigate the effect of the surface structure of dye-sensitized photocatalyst nanoparticles, we prepared three types of RuII -photosensitizer (PS)-double-layered Pt-cocatalyst-loaded TiO2 nanoparticles with different surface structures, Zr-RuCP6 -Zr-RuP6 @N wt %Pt-TiO2 , RuCP6 -Zr-RuP6 @N wt %Pt-TiO2 , and RuCP2 -Zr-RuP6 @N wt %Pt-TiO2 (N=0.2, 1, and 5), and evaluated their photocatalytic H2 evolution activity in the presence of redox-reversible iodide as the electron donor. Although the driving force of the electron injection from I- to the photo-oxidized RuIII PS is comparable, the activity increased in the following order: RuCP2 -Zr-RuP6 @1 wt %Pt-TiO2 < RuCP6 -Zr-RuP6 @1 wt %Pt-TiO2 < Zr-RuCP6 -Zr-RuP6 @1 wt %Pt-TiO2 . The apparent quantum yield of Zr-RuCP6 -Zr-RuP6 @1 wt %Pt-TiO2 in the first hour reached 1 %. Zeta-potential measurements suggest that the surface Zr4+ -phosphate groups attracted I- anions to the nanoparticle-solution interface. Our results indicate that the surface modification of dye-sensitized photocatalysts is a promising approach to enhance photocatalytic activity with various redox mediators.