Abstract
Holmium-TiO2 thin films were fabricated by a sol-gel technique. Holmium-TiO2 thin films were identified by many characterization techniques, such as UV-Vis, TEM, XPS, BET and XRD. The performance of the holmium-TiO2 thin film photocatalyst was studied by studying methanol preparation from the photocatalytic reduction of carbon dioxide under visible light. The results showed that holmium-TiO2 thin film photocatalytic properties can be adjusted by adjusting the holmium weight percent. XPS results revealed that holmium species were present as Ho3+ ions due to the presence of a peak for Ho3d(5/2) at 163.1 eV. BET results reveal that the addition of holmium to TiO2 led to an increase in the BET surface area of the TiO2 thin film. Additionally, the addition of holmium species decreased the band gap and increased the e-h recombination rate of titanium dioxide thin films. The highest photocatalytic activity and lowest band gap of the holmium-TiO2 thin film were achieved at 0.4 wt % holmium. The yield of methanol obtained using a 0.4 wt % Ho/TiO2 thin film is approximately 32 times that of the TiO2 thin film. The Holmium-TiO2 thin film has stable photocatalytic activity until five times for methanol preparation from the photocatalytic reduction of carbon dioxide under visible light.