Improved degradation of acetaminophen with NiO-TiO2 nanofibers synthesized through atomic layer deposition

Light-driven water treatment methods have garnered significant attention for their ability to effectively degrade harmful pollutants. In this study, polyvinylpyrrolidone (PVP)-based titanium dioxide nanofibers were synthesized using a sol–gel method combined with electrospinning, followed by calcination at 500 °C. Nickel oxide (NiO) layers of 5, 10, and 20 nm thickness were subsequently deposited onto the nanofibers via atomic layer deposition (ALD) using bis(ethylcyclopentadienyl)nickel and ozone as chemical precursors. The structural and functional properties of the fibers were characterized using electron microscopy, surface area analysis, and various spectroscopic techniques. The incorporation of NiO into TiO₂ nanofibers enhanced light absorption, suppressed charge recombination, and improved photocatalytic performance under visible light, as confirmed by reflectance and photoluminescence spectra. Photocatalytic tests demonstrated that fibers with 5 nm NiO exhibited superior performance, achieving 91 % degradation of acetaminophen under visible light within 4 h, compared to 70 % for bare TiO₂. Moreover, the 5 nm NiO-coated fibers maintained their performance over five cycles, with a slight reduction of 28 %. Reactive species analysis revealed the involvement of hydroxyl and superoxide radicals in the degradation process. Density functional theory (DFT) calculations further elucidated that the enhanced photocatalytic efficiency of the NiO (5 nm)-TiO₂ composite (denoted as N5T) stems from optimized electron-hole separation and improved photon energy retention. These findings highlight the potential of N5T nanofibers for water treatment applications and provide valuable insights for the development of advanced light-driven catalysts.