Abstract
Photocatalysis offers a promising method for water treatment, utilizing light-activated photocatalysts to trigger chemical reactions that degrade organic pollutants. In this study, composite fibers of polyvinylpyrrolidone (PVP) and titanium dioxide (TiO2) were synthesized using sol–gel process and electrospinning techniques, by integrating controlled concentrations of nickel oxide (NiO) ranging from 1 to 5 wt%, followed by calcination at 500 ◦C. The structural and morphological properties of these nanocomposites were meticulously characterized using a suite of advanced analytical techniques, including scanning and transmission electron microscopy, Brunauer-Emmett-Teller (BET) analysis, Raman spectroscopy, X-ray diffraction and photoelectron spectroscopy. These analyses revealed that the introduction of NiO into the TiO2 matrix not only modified the structural characteristics but also enhanced the optical properties, as demonstrated by the reflectance and photoluminescence spectra of the fibers. Photocatalytic performance was assessed through the degradation of acetaminophen under visible light, where NiO-TiO2 nanocomposites containing 5 wt% NiO achieved a 98.8 % degradation after 4 hours, demonstrating a significant enhancement compared to the 6 hours needed for pure TiO2 nanofibers. Thermal regeneration at 500 ◦C effectively restores the photocatalytic efficiency of 5 wt% NiO-TiO2 after a gradual decline over five cycles. Furthermore, acute toxicity and scavenging tests indicated that hydroxyl radicals (OH•-), superoxide anions (O2•-), and holes (h+) played significant roles in the degradation process. Density Functional Theory (DFT) calculations provided detailed insights into the electronic structure, band gaps, and charge transfer processes, revealing the mechanisms by which NiO-TiO2 composites achieve enhanced photocatalytic efficiency through optimized electron-hole separation and photon energy retention. These results underscore the potential of NiO-TiO2 composite nanofibers for photocatalytic applications and open pathways for the development of customizable photocatalysts tailored to specific environmental challenges.