Photoelectrochemical and photocatalytic properties of multilayered TiO2 thin films with a spinodal phase separation structure prepared by a sol-gel process

Multilayered titanium dioxide thin films with a spinodal phase separation structure were prepared by the sol-gel process from sols containing polyoxyethylene(20) nonylphenyl ether (NPE-20), and their photoelectrochemical and photocatalytic properties were investigated. The obtained films showed much higher anodic photocurrent and photocatalytic activity than the dense TiO2 thin film electrodes. We explained these phenomena by the large specific Surface area inherent in the spinodal phase separation structure and the higher concentration of Ti3+ species, which were produced by the reducing action of the incorporated organic polymers at sintering temperatures. Ti3+ species in the bulk raise the donor density, and those at the surface provide a larger number of active sites available for photoelectrochemical reaction and photocatalytic reaction.