Tuning the Structural Properties of TiO2 by Mo Doping for Efficient Photocatalytic Degradation of Methyl Orange

Muhamad Akif Aizuddin, Bin Jasni (2022) Tuning the Structural Properties of TiO2 by Mo Doping for Efficient Photocatalytic Degradation of Methyl Orange. Masters thesis, UNIVERSITI MALAYSIA SARAWAK (UNIMAS).

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Abstract

The photocatalytic activity of molybdenum (Mo) doped titanium dioxide (TiO2) derived photocatalyst is largely governed by an optimal dopant concentration and synthesis pathway. Nevertheless, much uncertainty still exists regarding the relationship between the concentration of Mo and the physicochemical properties of the resulting products and their photoactivity owing to discrepancy in related literature. In this study, the effect of different concentrations of TiO2-Mo photocatalysts (1 wt% - 10 wt%) synthesized by a facile wet impregnation method on the physicochemical changes and photocatalytic degradation performance was investigated. The recyclability performance of TiO2-Mo and its photocatalytic performance under different operating parameters which include dopant concentration, photocatalyst dosage, initial methyl orange (MO) concentration, initial pH and radical scavenger was investigated. The characterization of TiO2-Mo photocatalyst using XRD, XPS, FTIR, SEM, TEM, EDX and UV-DRS analysis indicate successful inclusion of Mo on TiO2. Mo doping has favourably induced changes in surface morphology, crystallite size and optical absorption, which have collectively enhanced the photocatalytic performance of TiO2-Mo photocatalyst on the removal of MO. The crystallite size of anatase TiO2 increases from 22.1 nm to 44.3 nm with increasing dopant concentration. The SEM analysis demonstrated that cluster of TiO2-Mo nanoparticles appeared to be more obvious with increasing Mo dopant concentration. The absorption intensity of TiO2-Mo in UV region is higher at high Mo concentration. The particle size and the specific surface area of TiO2 decreased from 82 nm to 95 nm and 52 m2/g to 6 m2/g, respectively upon Mo doping. Based on the preliminary experiments, 3 wt% provide best performing photocatalyst and was chosen for optimization study. The optimized TiO2-Mo (3 wt%) photocatalyst successfully removed 94.5% MO after 120 min of treatment time upon UVA irradiation (λ = 365 nm) under solution pH of 7.8. However, TiO2-Mo photocatalyst demonstrated lower photocatalytic performance of 22.8% under halogen light irradiation than that of undoped TiO2 (41.1%). Scavenger study revealed that reactive oxygen species greatly controlled the photocatalytic activity of TiO2-Mo photocatalyst whereby low concentration of reactive oxygen species scavenger inhibits the MO removal. This study provides a fresh insight of Mo as a promising dopant for TiO2 fabricated by a facile wet-impregnation method with an enhanced photocatalytic removal of dye wastewater by optimizing the synthesis conditions.

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