Mechanosynthesis of Mesoporous Bi-Doped TiO 2 : The Effect of Bismuth Doping and Ball Milling on the Crystal Structure, Optical Properties, and Photocatalytic Activity.

In this work, we reported obtaining mesoporous Bi-doped TiO₂ by mechanosynthesis and bismuth loading of 0%, 1%, 3%, 5%, and 10% (milled TiO₂, TiO₂ Bi 1%, TiO₂ Bi 3% TiO₂ Bi 5%, and TiO₂ Bi 10%, respectively). The effect of bismuth doping and ball milling on the crystal structure, optical properties, and photocatalytic performance of Bi-doped TiO₂ mesoporous samples under UV, visible, and sun irradiation was investigated. According to the results of the Rietveld refinement, the estimated chemical formulas for the TiO₂ Bi 1%, TiO₂ Bi 3%, TiO₂ Bi 5%, and TiO₂ Bi10% samples were Ti_0.99Bi_0.01O₂, Ti_0.97Bi_0.03O₂, Ti_0.96Bi_0.04O₂, and Ti_0.91Bi_0.09O₂ respectively. The incorporation of Bi into the TiO₂ lattice causes the crystallite size to decrease and, consequently, the absorption spectrum of TiO₂ to extend into the visible region of the electromagnetic spectrum, resulting in a lower band gap (E_g) value. Bi-doped TiO₂ mesoporous samples had E_g values of 2.90 eV, 2.83 eV, 2.77 eV, and 2.70 eV for the TiO₂ Bi 1%, TiO₂ Bi 3%, TiO₂ Bi 5%, and TiO₂ Bi 10% samples, respectively. Photocatalytic removal of methylene blue (MB) data fit well for second-order kinetics. Photocatalytic activity increase followed the order of TiO₂ Bi 5% > TiO₂ Bi 10% > TiO₂ Bi 3% > TiO₂ Bi 1% > pristine TiO₂. The TiO₂ Bi 5% sample exhibited excellent photocatalytic performance for MB photodegradation under natural sunlight (89.2%). [ABSTRACT FROM AUTHOR]