Effect of different plasmonic metals on photocatalytic degradation of volatile organic compounds (VOCs) by bentonite/M-TiO_2 nanocomposites under UV/visible light

摘要

Metal loaded clay/TiO2 nanocomposites have gained a huge attention to acting as an alternative and effective photocatalyst for the removal and complete degradation of toxic pollutants in the presence of UV/Visible light. Here, we have synthesized bentonite/M-TiO2 nanocomposites (M = Ag, Au, Pd) by a simple and facile method. Metal nanoparticles (NPs) of Ag, Au, and Pd were loaded (1% by wt.) on clay/TiO2 nanocomposites to study their impact on their photocatalytic activity. Oxidation states of the deposited metal NPs were analyzed by X-ray photoelectron spectroscopy (XPS). From HRTEM analysis, the particle size was found to be 8-10 nm and 10-15 nm for the metal NPs and TiO2 NPs respectively. The bentonite/M-TiO2 nanocomposites possessed higher surface area (119-125 m(2)/g) as compared to unloaded bentonite/TiO2 nanocomposites (112 m(2)/g). Localized surface plasmon resonance (LSPR) peaks corresponding to different metal NPs (502, 503 and 541 nm for Pd, Ag and Au respectively) were observed from UV-Visible DRS spectra (diffuse reflectance spectroscopy), Metal NPs acted as electron sinks suppressing electron-hole recombination as depicted from PL spectra leading to an increase in exciton life time (2.50 ns to 2.60 ns) as observed from time resolved fluorescence spectroscopy. The prepared bentonite/M-TiO2 nanocomposites were found to be effective photocatalyst towards degradation of harmful volatile organic compounds (VOCs) like chlorobenzene and benzaldehyde under UV and visible light. The nanocomposite containing Ag was found to be highly active with a rate constant of 0.055 and 0.0178 min(-1) for chlorobenzene and 0.027 and 0.004 min(-1) for benzaldehyde degradation under UV and visible light respectively. One of the most important advantages of bentonite/M-TiO2 nanocomposites over the well-known commercial TiO2 photocatalyst, P25 was that it could be easily separated from aqueous dispersions by sedimentation after the reaction and could be reused for several times.