Boosting the Photocatalytic Behavior of PbS/TiO2 Nanocomposites via the Pulsed Laser Deposition of PbS Nanoparticles onto TiO2 Nanotube Arrays Under Various Helium Background Pressures

In this study, highly ordered titanium dioxide nanotubes (TiO2-NTs) have been synthesized using the electrochemical anodization procedure. Subsequently, the TiO2-NTs were successfully decorated with PbS nanoparticles (NPs) using the pulsed KrF-laser deposition (PLD) technique under vacuum and under different Helium background pressures (PHe) ranging from 50 to 400 mTorr. The prepared samples (PbS-NPs/TiO2-NTs) were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and UV–Vis and photoluminescence spectroscopies. XRD analyses confirmed that all TiO2-NTs crystallized in the anatase phase, while the PbS-NPs crystallized in the cfc lattice. The average crystallite size of the (200) crystallites was found to increase from 21 to 33 nm when the pressure of helium (PHe) was raised from vacuum to 200 mTorr and then dropped back to ~22 nm at PHe = 400 mTorr. Interestingly, the photoluminescence intensity of the PbS-NPs/TiO2-NTs samples was found to start diminishing for PHe ≥ 200 mTorr, indicating a lesser recombination rate of the photogenerated carriers, which also corresponded to a better photocatalytic degradation of the Amido Black (AB) dye. Indeed, the PbS-NPs/TiO2-NTs samples processed at PHe = 200 and 300 mTorr were found to exhibit the highest photocatalytic degradation efficiency towards AB with a kinetic constant 130% higher than that of bare TiO2-NTs. The PbS-NPs/TiO2-NTs photocatalyst samples processed under PHe = 200 or 300 mTorr were shown to remove 98% of AB within 180 min under UV light illumination.