TiO2 film was applied to graphite substrate through chemical bath deposition (CBD) method with TiCl4 as precursor. CdS was deposited on TiO2/graphite (TiO2/G) by CBD with precursors of CdSO4. 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 TiO2 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. TiO2/G provide energy gap at 3.0 eV, which indicates that rutile phase is dominant. Meanwhile, CdS-TiO2/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-TiO2/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 TiO2/G and TiO2-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.

This paper discuss research about the optical properties and photo catalytic activity of TiO2 film on graphite substrate and its modification with ZnS. The optical properties investigated are the light response at various light wavelength and the gap energy (Eg). Meanwhile, the photocatalytic activity was studied from isopropanol degradation to determine the Quantum Yield (QY) and kinetics of reaction. The results show that the TiO2 layer is consisted of rutile and anatase phases. Meanwhile, the ZnS peaks are at 2θ 27.91 o and 54.58 o . The gap energy of TiO2/G consist of two band gap representing the band gap of rutile and anatase. The ZnS deposition shifted the band gap into single gap of 3.40 eV which is in between the gap energy of single TiO2 and single ZnS. The isopropanol degradation with TiO2/G photocatalyst under visible light radiation did not produce any new peaks representing product. Meanwhile, the photocatalytic process under 380 nm light produce new peaks representing the electronic transition of acetone. The isopropanol degradation with ZnS-TiO2/Graphite produced new peaks that indicates the photocataytic activity of ZnS-TiO2/Graphite whether under UV or visible light radiation. Significant role of ZnS also proven by the increase of the QY values and the increase of rate constant, k.

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