SYNTHESIS OF BIVO4 DOPED CO NANOPARTICLES AND FILM AS PHOTOCATALYST MATERIALS FOR METHYL ORANGE AZO BOND (-N=N-) CLEAVAGE

• Main Author: Adhaina, Karina
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/87273
• Institution: Institut Teknologi Bandung

The azo bond (-N=N-) in methyl orange dye is a very stable chemical bonding, making it difficult to degrade naturally in the environment. This dye can cause serious environmental problems due to its toxic nature and become a persistent organic pollutant. One promising approach to overcome this problem is through a process of breaking the azo double bond by photocatalysis. This method involves semiconductor materials that can utilize light energy, such as bismuth vanadate (BiVO4). BiVO4 is an n-type semiconductor material with a monoclinic Scheelite structure that has a narrow band gap energy of 2.4 eV due to the energy difference between the 6s orbital of Bi3+ and the 3d orbital of V5+. This narrow band gap is considered ideal for photocatalytic processes in the visible light region. However, the low electron mobility and high electron-hole recombination rates reduce its photocatalytic effectiveness. Modification of this material is carried out to prevent electron-hole recombination by dispersing Co2+ on the BiVO4 surface as a charge trap. In this study, BiVO4 films were obtained by the doctor blade method using BiVO4 powder synthesized by the hydrothermal method with citric acid, and ethylene glycol as precursors, binders, and solvents. In the cobalt-doped BiVO4 film, Co2+ ions were added to the BiVO4 film by spreading cobalt(II) nitrate solution on the surface of the prepared BiVO4 film. X-ray diffraction (XRD) patterns showed that the film samples were polycrystalline with a monoclinic Scheelite structure. In addition, a significant increase in intensity was observed in the (040) plane. With a comparison to the bulk samples, the BiVO4 film has a tendency for the crystal to grow towards the b-axis. Surface modification with Co2+ ions did not show any changes in the crystal structure of BiVO4, indicating that the Co2+ ions were only present on the surface. The optical properties of the films were analyzed by UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The band gap energy (Eg) of the film was determined using the Tauc plot, and the value was obtained at 2.51 eV for the direct allowed electronic transition. The Co-doped BiVO4 film showed two absorption edges at 2.28 eV and 1.45 eV for the direct allowed electronic transition, indicating the presence of defect states originating from the incorporation of cobalt on the surface. The photocatalytic performance of the azo bond cleavage reaction (-N=N-) of methyl orange was carried out under under visible light (? = 380 ? 680 nm, 18 W) at room temperature for 90 minutes with a concentration of 5 ppm. The results showed that the percentage of degradation reached 90%, following the zero order reaction kinetics with the value of rate constant (k) of 3,67833 × 10?3 ± 4,79039 × 10-4 a.u. minutes?1.