Highly effective photocatalyst of TiO₂ nanoparticles dispersed on carbon nanotubes for methylene blue degradation in aqueous solution

Abstract

In the present study, titania nanoparticles are highly dispersed on carbon nanotubes via hydrolysis process of tetra- isopropyl-orthotitanate Ti[OCH(CH₃)₂]₄ (TPOT). The obtained composite (TiO₂/CNTs) is characterized by modern methods. The anatase-TiO₂ phase is realized based on X-ray diffraction spectrum at different pHs of hydrolysis solution. The band gap of TiO₂/CNTs (Eg) is calculated by Tauc method using diffuse reflectance spectroscopy (DRS). The TiO₂/CNTs composite plays as an active photocatalyst for methylene blue (MB) decomposition in aqueous solution. The effect of time to photocatalytic ability of TiO₂/CNTs composite is described using Langmuir- Hinshetwood kinetic model. The values of enthalpy variation (ΔH), entropy change (ΔS) and Gibbs free energy variation (ΔG) of the decomposition of MB are determined from thermodynamic study. In the range temperature from 283 K to 323 K, the positive values of ΔH and negative value of ΔG confirms endothermic and spontaneous nature of MB degradation. With the increase of temperature, the reaction occurs more easily, which is proved by more negative values of Gibbs free energy calculated from Van't Hoff equation.