Electrochemical Applications Reveal Enhanced Photocatalytic Performance of TiO2-Doped ZnS Nanocomposites.

Abstract

The titanium dioxide (TiO₂) nanoparticles were prepared by hydrothermal methods at ambient temperature. Based on XRD analysis, the average crystallite size of pure TiO₂ nanoparticles and those doped with ZnS was calculated to be 58 and 54 nm, respectively. At an angle of 25.4°, the prominent peak observed at the (101) plane of TiO₂ was confirmed. As can be seen from the collection of peaks, the TiO₂ formed has an anatase-type tetragonal crystal structure. A strain of -6.4541 × 10^-4 and a grain size of 33 nm can be seen in the W-H plot for TiO₂ nanoparticles. For doped ZnS nanoparticles, on the other hand, the values are 1.9448 × 10^-4 and 47 nm. In our study, we found that doped nanoparticles were average grain size 134 nm, while pure nanoparticles were average grain size 146 nm. Doping reduces the size of the nanomaterial, which means that the TiO₂ molecules form nanoclusters on their surfaces, which can lead to a larger grain size for a pure nanoparticle than for a doped nanoparticle. A wide range of functional groups and their associated bonds were investigated using FTIR spectra in synthesized nanomaterials. TiOTi bonds are subjected to a strong stretching vibration, which is confirmed by the absorption peaks from 450 cm^-1 to 800 cm^-1. The PL spectra for pure TiO₂- and ZnS-doped TiO₂ containing nanocomposites of ZnS emit ultraviolet light at wavelengths of 362 and 379 nm in the UV region. Pure and doped samples with optical bandgap energies of ~3.04 and ~3.8 eV corresponding to anatase phases were near ~3.18 eV in Tauc plots. Since the TiO₂-doped ZnS heterojunction migrates photoexcited holes toward the interface, while electrons migrate toward the bulk, this results in photoexcited holes migrating toward the interface. To calculate the specific capacitance of the synthesized materials, cyclic voltammetry with pure ZnS and those with ZnS-doped had specific capacitance values of 144.91 F/g and 120.11 F/g, respectively. The catalysts used were ZnS nanocomposite doped with TiO₂ in addition to pure TiO₂ nanoparticles. The degradation of dye within 80 min after sunlight exposure was monitored with a UV-Vis spectrophotometer at 20-min intervals. ZnS nanoparticles doped with TiO₂ display 87.8% greater efficiency than pure nanoparticles. Doped TiO₂ nanocomposite degrades at an 87.8% rate, whereas pure TiO₂ degrades at ~54%, indicating that the dopants enhance photocatalysis.