Photocatalytic Activity Of P25 Research Articles

Evaluation of Solar-Driven Photocatalytic Activity of Thermal Treated TiO₂ under Various Atmospheres.

In this report, the photocatalytic activity of P25 has been explored and the influence of thermal treatment under various atmospheres (air, vacuum and hydrogen) were discussed. The samples’ characteristics were disclosed by means of various instruments including X-ray diffraction (XRD), Electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and UV–vis. This study also accentuates various states of the oxygen vacancy density formed inside the samples as well as the colour turning observed in treated P25 under various atmospheres. Produced coloured TiO2 samples were then exploited for their photocatalytic capability concerning photodegradation of methylene blue (MB) using air mass (AM) 1.5 G solar light irradiation. Our findings revealed that exceptional photocatalytic activity of P25 is related to the thermal treatment. Neither oxygen vacancy formation nor photocatalytic activity enhancement was observed in the air-treated sample. H2-treated samples have shown better photoactivity which even could be further improved by optimizing treatment conditions to achieve the advantages of the positive role of oxygen vacancy (O-vacancy at higher concentration than optimum acts as electron trapping sites). The chemical structure and stability of the samples were also studied. There was no sign of deteriorating of O2-vacancies inside the samples after 6 months. High stability of thermal treated samples in terms of both long and short-term time intervals is another significant feature of the produced photocatalyst.

Improvement Photocatalytic Activity of P25 by Modification with a Rare Earth-Free Upconversion Nanocrystal.

It has been reported that coupling TiO2 with rare earth upconversion nanocrystals (UCNCs) is an efficient strategy to significantly improve photocatalytic activity of TiO2. However, the rare earth materials are scarcity and cost, and the synthesis process of UCNCs using the rare earth materials is complicated. In the present study, we have designed a new approach using a rare earth-free upconversion nanocrystal (REF-UCNCs) as upconversion luminescent material to replace the rare earth UCNCs. A novel nanocomposite photocatalyst of REF-UCNCs@P25: Mo/GN was developed for the first time. Based on the designed structure, the REF-UCNCs, Mo-doping, and GN (graphene) have a synergistic effect that can improve catalytic activity of P25 significantly. The results of photocatalytic experiments using RhB as a model pollutant under simulated solar light irradiation show that the photocatalytic efficiency of the as-prepared catalyst is 3-folds higher than that of benchmark substance P25. This work provides a new strategy for efficiently improving catalytic activity of semiconductor photocatalysts by coupling with REF-UCNCs. This approach is facile and low-cost which can be widely applied for modification of semiconductor photocatalysts and facilitates their applications in environmental protection issues using solar light.

Highly active P25@Pd/C nanocomposite for the degradation of Naphthol Blue Black with visible light

TiO2-P25 supported Pd/C (P25@Pd/C) composite was prepared by the solid state dispersion method. The prepared composite was characterized by XRD, Raman, PL, SEM and DRS measurements. The photocatalytic activity of the composite was tested towards Naphthol Blue Black (NBB) azo dye degradation under visible light. The photocatalytic activity of P25 was highly influenced by Pd/C. Almost complete degradation was achieved with P25@Pd/C in 120 min, and found to be more efficient when compared with pristine Degussa-P25. The composite was reused in four cycles without loss of activity. A mechanism was proposed for NBB degradation by P25@Pd/C composite under visible light.

Optimization of defect distribution in photodegradation of air pollutants via SiO2-shell-enhanced fluorine modification

The distribution of bulk and surface defects significantly affects the separation and injection of photogenerated charge carriers. In this study, we provide a strategy of SiO2-shell-enhanced F modification to optimize the distribution of bulk and surface defects. The effects of SiO2 coating and F modification on the physical structure, the separation behavior of photogenerated charge carriers, and the photocatalytic activity of P25 were studied by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, surface photovoltage spectroscopy, and toluene degradation experiments. Results showed that the removal rate of toluene over SiO2-F-modified P25 was significantly higher than those over P25 and F modified P25. The SiO2-shell-enhanced F modification simultaneously increased the content of surface Ti3+ and reduced the bulk defects, thereby enhancing the separation of charge carriers. Furthermore, F doped at surface exerted a strong catalytic effect on the removal of toluene, whereas F doped in lattice caused the recombination of photogenerated charge carriers. The SiO2 coating and calcination treatment significantly increased the amount of F ions doped at TiO2 surface and inhibited F doping in lattice.

Effect of montmorillonite on the photocatalytic activity of TiO 2 nanoparticles

In the present work, the degradation of methyl orange in water was used to examine the effect of montmorillonite on the photocatalytic activity of TiO 2 nanoparticles (P25). Meanwhile, the role which montmorillonite plays in the photocatalysis was explored with UV–visible diffuse reflectance spectra (DRS) and electrophoresis. It is found that montmorillonite can inhibit the photocatalytic decomposition of methyl orange, but the photocatalytic activity of P25 will be enhanced obviously at a certain concentration of montmorillonite. The enhanced photocatalytic activity might be ascribed to the light scattering induced by the montmorillonite particles. Additionally, the effect of montmorillonite on the photocatalytic activity of P25 was studied as functions of pH of the solution, initial concentration of methyl orange, and reaction atmosphere.

Cross-flow microfiltration with periodical back-washing for photocatalytic degradation of pharmaceutical and diagnostic residues–evaluation of the long-term stability of the photocatalytic activity of TiO2

The combination of semiconductor photocatalysis with cross-flow microfiltration accompanied by periodical back-washing was investigated in a pilot plant. The investigation included the testing of membrane materials because the membrane must resist the abrasion and the periodical back-washing. Another objective of this investigation was to assess the potential of two different TiO(2) materials (Hombikat UV100 and P25) for continuous photocatalytic degradation of persistent organic pollutants. The study focused on the long-term stability of the photocatalytic activity of TiO(2) during its continuous application. The combination of photocatalysis and cross-flow microfiltration allowed the separation and reuse of TiO(2) after the photocatalytic degradation of clofibric acid, carbamazepine and iomeprol. The investigations showed that the photocatalytic activity of P25 and Hombikat UV100 was constant during continuous usage over several days. This study indicates the high potential of the combination of heterogeneous photocatalytic oxidation processes with cross-flow microfiltration accompanied by periodical back-washing of the membrane. Thus environmentally relevant pharmaceuticals and X-ray contrast media can be transformed and mineralized in a continuous water treatment process.

Role of Platinum Deposited on TiO2 in Phenol Photocatalytic Oxidation

Photooxidation of phenol has been studied in aqueous suspensions of titanium dioxide Hombikat UV100 and Degussa P25 loaded with various amounts of Pt. The rates of phenol decomposition and total carbon removal rose by a maximum factor of 1.5 when Hombikat was loaded with 1 wt % Pt; further increase of Pt deposition did not increase the photoactivity any more. The electron movement across the Pt−anatase junction is discussed, and the positive influence of Pt on phenol oxidation over Hombikat is explained by the increase of charge separation in agglomerates of primary particles. The photocatalytic activity of P25 was higher than that of platinized and pure Hombikat. But loading P25 with Pt resulted in a decrease of phenol decomposition and total carbon removal rates. The decrease of Degussa P25 activity after platinization means that Pt cannot further increase the efficiency of charge separation in this TiO2, whose two-phase composition already provides a very efficient suppression of recombination in liqui...