Platinum-loaded lanthanum-doped calcium titanate photocatalysts prepared by a flux method for photocatalytic steam reforming of methane

Abstract Calcium titanate (CaTiO3) samples were prepared by a flux method with various parameters such as the selection of the flux, presence or absence of the flux, and solute concentration in the molten mixture with the flux. These conditions much influenced the structural and physical properties like morphology, particle size, specific surface area, and photoabsorption bands. The photocatalytic activity of the samples loaded with Pt-cocatalyst (Pt/CaTiO3) were evaluated for the photocatalytic steam reforming of methane around room temperature. It was found that the sample prepared by the flux method realized 3.3 times higher photocatalytic activity than that by a conventional solid state reaction method. Further, La-doping to the CaTiO3 photocatalyst (Pt/CaTiO3:La) was examined. It was revealed that La cation was successfully doped at the Ca site in the CaTiO3 lattice. It is observed that small amount of La-doping anomalously enhanced the crystal growth although it lowered the photocatalytic activity. In contrast, the sample with a moderate amount of La-doping such as 1 mol% exhibited 1.6 times higher photocatalytic activity than the non-doped sample. Although most of the structural properties such as morphology, particle size and the specific surface area could not simply explain the improvement of photocatalytic activity, at least it was revealed that the defects giving rise to the absorption bands in visible light region decreased the photocatalytic activity.