Time-Resolved Infrared Absorption Study of NaTaO3 Photocatalysts Doped with Alkali Earth Metals

Electron-hole recombination kinetics was observed in NaTaO3 photocatalysts doped with Ca, Sr, Ba, and La using time-resolved infrared absorption. The recombination rate was compared with the ultraviolet light-derived H-2 production rate in the water splitting reaction to estimate the electron-to-H-2 conversion efficiency. The conversion efficiency was sensitive to the nanometer-scale topography of the photocatalyst surface. The particularly high efficiency on the nondoped and 0.5 mol % Sr-doped photocatalysts was related to the flat (100) crystalline surfaces exposed on the photocatalyst particles. The mobility of holes was suggested to be restricted by doping on the basis of a kinetic simulation of the recombination rate.