Nanostructured boron and copper oxide modified tio2 for the photocatalytic treatment of methylene blue /
Md Noor Bin Arifin
- xvii, 252 pages : illustrations ; 30 cm.+ 1 CD-ROM
Faculty of Chemical and Process Engineering Technology
Thesis (Doctor of Philosophy) -- Universiti Malaysia Pahang – 2025
Includes bibliographical references
Titanium dioxide (TiO2), despite its excellent photocatalytic properties, suffers from limitations such as a wide band gap, which restricts visible light absorption, and rapid electron-hole recombination, reducing its efficiency. While single doping with copper oxide (CuO) or boron (B) improves either charge separation or light absorption, each modification alone is insufficient for optimal performance. Therefore, this thesis aims to develop a ternary copper oxide and boron doped titanium dioxide (CuO/B-TiO₂) photocatalysts with heterojunction architecture which addresses the inherent setbacks of TiO2 and single doped TiO2. This can be achieved by lowering the band gap and providing the charge carriers pathway and sites for photo redox utilization. For this purpose, a ternary CuO/B-TiO2 photocatalyst was synthesized via the sol-gel method. All of the as-synthesized photocatalysts were characterized using XRD, UV-vis DRS, PL, XPS and FESEM. The optimal loadings were then determined as 6 wt.% boron doped titanium dioxide (B-TiO2) and 1 wt.% CuO/TiO2, corresponding to the 93% and 95% decolorization efficiency in 120 minutes. The co-doping formula of 6 wt.% boron and 1 wt.% CuO was chosen to construct the heterojunction 1,6-CuO/B-TiO2 photocatalysts, which demonstrated the highest decolourization of MB, standing at 99% decolorization efficiency within 120 mins of visible light irradiation. The optimal achievement of removal efficiency was rendered by the modified properties, suitable band gap energy (2.51 eV) and low recombination of electron-hole pairs. The XPS results indicated that the substitution of B into O lattice structure was successful from the existence of 192.01 eV binding energy, exuded by the B-O bond in B2O3. the presence of reduced copper species such as Cu+ or Cu is validated by the obtained binding energy of 952.5 eV. LSV and cyclic voltammetry (CV) also showed a distinguished charge transfer efficiency and electron transfer kinetics for 1,6-CuO/B-TiO2, indicated by the highest current density of 0.3238 mA/cm2 under visible light irradiation and lowest overpotential at -0.9529 V (vs. NHE). The scavenger experiment revealed that hydroxyl radical, ·OH is the main radical, in line with the thermodynamic assessment that also confirmed the plausible oxygen reduction reaction to form ·OH (O2/·OH = 0.701 V vs NHE) and H2O2 (O2/H2O2 = 0.695 V vs NHE). Mott-Schottky analysis indicated a Type II heterojunction of CuO/B-TiO2 where the electrons are believed to have migrated from the CB of CuO to the CB of TiO2 and the counter migration of holes at the valence band (VB) of B-TiO2 to the VB of CuO. A first-order kinetic model was proposed and demonstrated to be an excellent fit for MB photocatalytic decolorization, as evidenced by the high R2 value, 0.98. This research provides insights into a novel 1,6-CuO/B-TiO2 photocatalysts development for sustainable wastewater treatment.
THE0010170 (Local)
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