Effect of Silver Concentration on the Photocatalytic Activity of a Nanocomposite Based on Titanium Dioxide Nanorods and Reduced Graphene Oxide
Abstract
This study investigates the influence of Ag nanoparticle concentration on the photocatalytic activity of films made of titanium dioxide nanorods (TNR) and reduced graphene oxide (rGO) sheets. TNRs were synthesised using a hydrothermal method. Using chemical reduction, Ag nanoparticles with varying concentrations and diameters of 5–12 nm were obtained on the surface of TNR. The rGO sheets were deposited onto the surface of TNR and Ag nanoparticles from a phosphate solution using an electrochemical method. From SEM images, it was established that as a result of hydrothermal synthesis, TNRs with a length of ~3.2 μm and an average diameter of 50-70 nm are formed on the surface of the substrate, and Ag nanoparticles and rGO sheets are evenly distributed over their surface. XRD and Raman spectroscopy methods confirmed the preservation of the rutile phase of TNR and the successful incorporation of Ag and rGO into the nanocomposite structure. The increase in the concentration of Ag nanoparticles on the surface of TNR and rGO leads to an expansion of spectral sensitivity in the visible range from 300 to 480 nm due to intrinsic absorption and the surface plasmon resonance (SPR) effect, which results in a decrease in the bandgap width from 3.3 eV to 2.9 eV. In addition, by adding Ag nanoparticles and rGO sheets to the TNR structure, it was possible to reduce the resistance to transfer of charge carriers by 20 times and the effective electron lifetime by 2.7 times. The photocatalytic activity of the nanocomposites was evaluated based on the degradation of methylene blue (MB), Congo red (CR) and rhodamine B (RhB) dyes. The rate of dye degradation increased with increasing concentrations of Ag nanoparticles and rGO incorporation, and was 3.2, 3.1 and 1.4 times higher for MB, CR, and RhB, respectively, compared to pure TNR. Based on the results obtained, it can be assumed that the introduction of Ag plasmonic nanoparticles increases the absorptive capacity of the material, reduces its resistance, and promotes the effective separation and transport of charge carriers, which leads to an increase in their photocatalytic activity.