Highly-efficient photocatalytic degradation of methylene blue by PoPD-modified TiO 2 nanocomposites due to photosensitization-synergetic effect of TiO2 with PoPD

Abstract

Poly-o-phenylenediamine modified TiO2 nanocomposites were successfully synthesized via an ‘in situ’ oxidative polymerization method. The modified nanocomposites were characterized by BET, XRD, TEM, FT-IR, TGA, XPS, EA and UV-Vis DRS. The photocatalytic degradation of methylene blue was chosen as a model reaction to evaluate the photocatalytic activities of TiO2 and PoPD/TiO2. The results indicated that PoPD/TiO2 nanocomposites exhibited good photocatalytic activity and stability. The photocatalytic activity of PoPD/TiO2 increased as the initial pH increased because of electrostatic adsorption between the photocatalyst and MB as well as the generation of ·OH, whereas it exhibited an earlier increasing and later decreasing trend as the concentration of the photocatalyst increased owing to the absorption of visible light. The photocatalytic stability of the PoPD/TiO2 nanocomposite was dependent on the stability of its structure. Based on radical trapping experiments and ESR measurements, the origin of oxidizing ability of PoPD/TiO2 nanocomposites on photocatalytic degradation of MB was proposed, which taking into account of ·OH and ·O2 − were the first and second important ROS, respectively. The possible photocatalytic mechanism and photocatalytic activity enhanced mechanism has been proposed, taking into account the photosensitization effect and synergetic effect of TiO2 with PoPD.

The effect of surface charge on photocatalytic degradation of methylene blue dye using chargeable titania nanoparticles

“…On the other hand, TiO 2 NPs prepared at pH 1.6 exhibited lower efficiency (73%) due to the electrostatic repulsion between the positively charged NPs and the cationic dye. These results are fully matched with the previously published reports 38 .

Figure 8 Photodegradation efficiencies of TiO 2 NPs prepared at different pH values; 1.6, 7.0 and 10.

…”

Bimolecular proximity of a ruthenium complex and methylene blue within an anionic porous coordination cage for enhancing photocatalytic activity

“…The host–guest complex serves as a heterogeneous high-performance photocatalyst. Even compared to previously reported MOFs, Ru@PCC-2 has its unique advantages;25,26 first of all, the reaction does not involve any strong oxidizing agent, such H 2 O 2 , and the light source is just visible light, rather than UV light 24,27. A MOF photocatalyst ZnO@ZIF-8 achieved similar performance, but required high energy UV light (300 W high-pressure Hg lamp), instead of visible light (20 W) in our experimental setup 28.…”

“…Unlike most MOF photocatalysts, in which the frameworks contribute to the ligand-to-metal charge transfer (LMCT),24,27 PCC-2 plays the vital role of attracting both catalyst and substrates into its cavity, as well as offering the microenvironment for the reaction to take place (Fig. 6a).…”

Photocatalytic activity of graphene oxide–TiO 2 thin films sensitized by natural dyes extracted from Bactris guineensis

“…[97] reported a k app value of 7.3 × 10 −3 min −1 for photocatalytic degradation of MB after 300 min under visible light irradiation using Fe-doped TiO 2 thin films as photocatalyst. In another study, Yang et al [98] reported a k app value of 3.3 × 10 −3 min −1 for photocatalytic degradation of MB after 180 min using poly- o -phenylenediamine-modified TiO 2 nanocomposites as photocatalysts. Also, Jaihindh et al .…”