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 Ru(II)-photosensitizer(PS)-double-layered Pt-cocatalyst-loaded TiO 2 nanoparticles with different surface structures, Zr- RuCP 6 -Zr- RuP 6 @ N  wt%Pt-TiO 2 , RuCP 6 -Zr- RuP 6 @ N  wt%Pt-TiO 2 , and RuCP 2 -Zr- RuP 6 @ N  wt%Pt-TiO 2 ( N = 0.2, 1, and 5), and evaluated their photocatalytic H 2 evolution activity in the presence of redox-reversible iodide (I - ) as the electron donor. Although the driving force of the electron injection from I - to the photooxidized Ru(III) PS is comparable, the activity increased in the following order: RuCP 2 -Zr- RuP 6 @1 wt%Pt-TiO 2 < RuCP 6 -Zr- RuP 6 @1 wt%Pt-TiO 2 < Zr- RuCP 6 -Zr- RuP 6 @1 wt%Pt-TiO 2 . The apparent quantum yield (AQY) of Zr- RuCP 6 -Zr- RuP 6 @1 wt%Pt-TiO 2 in the first hour reached 1%. Zeta potential measurements suggest that the surface Zr 4+ -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 the photocatalytic activity with various redox mediators.