Characterization and Kinetic Study of TiO2/ ZnO Co-Doped with Nitrogen and Sulphur at Different Calcination Temperature

Abstract

TiO₂/ZnO nanocomposites, have garnered significant attention for their potential applications in environmental remediation and sustainable energy production. Doping these materials with non-metals like nitrogen and sulphur and using optimum calcination temperature holds promise for enhancing their photocatalytic efficiency. However, a comprehensive investigation into the impact of calcination temperature on nitrogen and sulphur co-doped TiO₂/ZnO nanocomposites remains relatively unexplored and limits their extensive use in photocatalysis and makes it difficult to customise the materials for particular purposes. Thus, in this study, nitrogen and sulphur co-doped TiO₂/ZnO nanocomposites were developed using a sol-gel method and the effect of calcination temperature (400oC - 800oC) on the chemical properties of TiO₂/ZnO-N, S nanocomposites was determined using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), and UV-visible spectroscopy. Based on the results, calcination temperature at 600oC gave the optimum characteristic of the catalyst and gave the highest photocatalytic efficiency. At 600oC, the mesoporous structure of TiO₂/ZnO-N,S was obtained with crystallite size of 15.6nm, 35.6% crystallinity, 22.81m2/g surface area and dense layer with less agglomeration on the surface. For optical properties, doping of nitrogen and sulphur into TiO₂/ ZnO able to narrow the band gap to 2.89eV. The kinetic studies of the reaction were studied with Langmuir, Freundlich and Langmuir-Hinshelwood (L-H) models. All the models were compared based on their R2 value and Langmuir adsorption equilibrium constant (Kads) to elucidate the optimum model for the photocatalytic reaction. The result show that the L-H model fitted better to the adsorption, and considered to follow pseudo first-order decay kinetics. The research seeks to provide insights into the design and development of efficient photocatalysts for environmental remediation applications.