TRANSITION METAL ION IMPREGNATED BIVO4 PHOTOCATALYST AND ITS PERFORMANCE FOR C=C BOND CLEAVAGE OF OLEIC ACID

• Main Author: Aulia Rahmah, Annisa
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/75032
• Institution: Institut Teknologi Bandung

Bismuth Vanadat (BiVO4) is one of the best photocatalyst candidates for oxidation reactions of organic compounds because it has an energy gap in the visible light range. However, BiVO4 has a high rate of electron-hole recombination, poor charge transfer, thus it reduces the effectiveness of oxidation reaction. In this study, surface modification of BiVO4 by impregnation of Co2+, Ni2+, and Cu2+ ions were carried out to inhibit the recombination of charge carriers by trapping electrons from the photocatalyst to dopants on the surface. The choice of metal ion is based on the energy level of the 3d orbital which is lower than V-3d. Thus, it is hoped that the excited electrons can move from the BiVO4 conduction band to the incomplete 3d orbital of the transition metal ion. BiVO4 photocatalyst was synthesized by hydrothermal method followed by impregnation with transition metal ions. X-ray diffraction (XRD) analysis showed that all samples consisted of monoclinic scheelite single phase. Further analysis showed an increase in the crystallite size of the surface modified samples. In the BiVO4-Ni and Cu samples, a significant increase in intensity was observed at the diffraction peak of the (040) plane. Surface modification with metal ions of Ni2+ and Cu2+ tends to increase the growth of crystals in the direction of the b axis, while the lattice parameters are not affected by impregnation indicating that the dopant ions do not enter the bulk phase and do not change the crystal structure of BiVO4. UV-Diffused Reflectance Spectroscopy (UV-DRS) characterization showed that the absorption band of BiVO4 was estimated from UV to a wavelength of 550 nm, while the surface modified photocatalyst showed increased absorption in the visible light region. The band gap energy (Eg) of BiVO4 is 2.4 eV. The direct electronic transition (direct allowed) of BiVO4-Co has 2 band gaps of 2.28 and 1.46 eV. Indrect band gap BiVO4-Co and Cu show narrow band defects, while BiVO4-Ni shows wide band defects. The study of photocatalyst performance on methylene blue (MB) degradation showed that BiVO4-Cu had the best photocatalytic activity under visible light irradiation (k = 3.99 ? 10-3 min-1). The order of degradation rate from highest to lowest is BiVO4-Cu > BiVO4-Co > BiVO4-Ni > BiVO4. The photocatalytic performance of the oxidation reaction of breaking the double bond (C=C) of oleic acid (AO) was carried out by varying the solvents: water and water/ethanol under visible light irradiation (? = 380-680 nm, 18 W), room temperature for 48 hours. The use of ethanol water solvent aims to maximize the adsorption of the substrate and photocatalyst. Gas Chromatography–Mass Spectrometry (GCMS) characterization showed that the BiVO4 photocatalyst was successful in breaking the double bond (C=C) of oleic acid compared to not photocatalyst. Photocatalyst using water solvent produces 9-oxononanoic acid and nonanal products, while photocatalyst using ethanol water solvent does not produce the desired reaction product. Water solvent greatly affects the photocatalyst reaction, and ethanol solvent does not show better reactivity than water. Water solvent plays an important role in producing reactive oxygen species in the oxidation reaction process. BiVO4-Co has two bandgap energy (Eg), both in direct allowed and indirect electronic transitions. This affects the oxidation reaction of breaking the double bond of oleic acid, 9- oxononanoate and nonanal were generated using BiVO4 and BiVO4-Co. The oxidation reaction using BiVO4-Ni with water as a solvent has a high % conversion but a low % selectivity. BiVO4-Ni has wide band defects in indirect electronic transitions resulting in other unwanted products.