pubs.acs.org/JPCL
Charge Separation and Trapping in N-Doped TiO2 Photocatalysts: A Time-Resolved Microwave Conductivity Study Ryuzi Katoh,*,† Akihiro Furube,† Ken-ichi Yamanaka,‡ and Takeshi Morikawa‡ †
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan, and ‡Toyota Central Research and Development Laboratories, Inc., Nagakute, Aichi 480-1192, Japan
ABSTRACT We studied charge separation and trapping processes in N-doped TiO2 (N-TiO2) photocatalysts by means of time-resolved microwave conductivity (TRMC). We observed that the trapping rate increased with N-doping due to the increase in the oxygen vacancy. Furthermore, the trapping rate increased markedly when Cu was loaded onto the photocatalysts, and this increase indicated a rapid electron transfer to this Cu cocatalyst. For N-TiO2, the charge separation efficiency under visible light excitation (450 nm, Ti 3d r N 2p transition) was found to be onethird as high as the efficiency observed under ultraviolet excitation (Ti 3d r O 2p transition). We discuss possible mechanisms for the charge separation and trapped processes, which is essential for the design of efficient doped-TiO2 photocatalysts. SECTION Surfaces, Interfaces, Catalysis
P
hotocatalysts based on TiO2 have attracted much attention as promising environmental photocatalysts, and a huge number of studies have been carried out on these materials.1-3 However, TiO2 photocatalysts absorb light only in the ultraviolet (UV) wavelength range (
