Optical properties and photocatalytic activity of CdS-TiO ₂ /graphite composite

Abstract TiO ₂ film was applied to graphite substrate through chemical bath deposition (CBD) method with TiCl ₄ as precursor. CdS was deposited on TiO ₂ /graphite (TiO2/G) by CBD with precursors of CdSO ₄ . A UV-Vis diffuse reflectance (UV-Vis DR) analysis was used to analyze the optical properties and band gap energy. Meanwhile, photocatalytic activity was determined from the quantum yield (QY) value of isopropanol degradation. The X-ray diffraction pattern shows that the TiO ₂ film contains rutile and anatase phases. UV-Vis DR spectrum shows the photoactivity in the visible light area and provides lower band gap value due to CdS deposition. TiO ₂ /G provide energy gap at 3.0 eV, which indicates that rutile phase is dominant. Meanwhile, CdS-TiO ₂ /G shows multiple energy gaps representing CdS at 2.4 eV, rutile at 3.0 eV, and anatase at 3.2 eV. The QY values of CdS-TiO ₂ /G are 7.98×10 ^-3 and 8.62×10 ^-4 at 450 and 380 nm of radiation light, respectively. These values are higher than the QY of TiO ₂ /G and TiO ₂ -P25/graphite (TiO2-P25/G), which are 1.19×10 ^-4 and 5.0×10 ^-4 , respectively. The photocatalytic reaction follows the first-order reaction. CdS deposition allows the rate constant to increase from 2×10 ^-3 to 13×10 ^-3 under UV radiation.