Photocatalysis

About: Photocatalysis is a research topic. Over the lifetime, 67088 publications have been published within this topic receiving 2145233 citations. The topic is also known as: photocatalyst.

The combination of heterogeneous photocatalysis with chemical and physical operations: A tool for improving the photoprocess performance

Abstract: Heterogeneous photocatalysis is a process of great potential for pollutant abatement and waste treatment. In order to improve the overall performance of the photoprocess, heterogeneous photocatalysis is being combined with physical or chemical operations, which affect the chemical kinetics and/or the overall efficiency. This review addresses the various possibilities to couple heterogeneous photocatalysis with other technologies to photodegrade organic and inorganic pollutants dissolved in actual or synthetic aqueous effluents. These combinations increase the photoprocess efficiency by decreasing the reaction time in respect to the separated operations or they decrease the cost in respect of heterogeneous photocatalysis alone, generally in terms of light energy. Depending on the operation coupled with heterogeneous photocatalysis, two categories of combinations exist. When the coupling is with ultrasonic irradiation, photo-Fenton reaction, ozonation, or electrochemical treatment, the combination affects the photocatalytic mechanisms thus improving the efficiency of the photocatalytic process. When the coupling is with biological treatment, membrane reactor, membrane photoreactor, or physical adsorption, the combination does not affect the photocatalytic mechanisms but it improves the efficiency of the overall process. The choice of the coupling is related to the type of wastewater to be treated. A synergistic effect, giving rise to an improvement of the efficiency of the photocatalytic process, has been reported in the literature for many cases.

High photocatalytic activity of ZnO-carbon nanofiber heteroarchitectures.

Abstract: One-dimensional ZnO−carbon nanofibers (CNFs) heteroarchitectures with high photocatalytic activity have been successfully obtained by a simple combination of electrospinning technique and hydrothermal process. The as-obtained products were characterized by field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and IR spectrum. The results revealed that the secondary ZnO nanostructures were successfully grown on the primary CNFs substrates without aggregation. And, the coverage density of ZnO nanoparticles coating on the surface of the CNFs could be controlled by simply adjusting the mass ratio of zinc acetate to CNFs in the precursor during the hydrothermal process for the fabrication of ZnO−CNFs heterostructures. The obtained ZnO−CNFs heteroarchitectures showed high photocatalytic property to degrade rhodamine B (RB) because of the formation of heteroarchitec...

Enhanced photocatalytic activity of Ce3+–TiO2 for 2-mercaptobenzothiazole degradation in aqueous suspension for odour control

Abstract: A series of cerium ion-doped titanium dioxide (Ce3+–TiO2) catalysts with special 4f electron configuration was prepared by a sol–gel process and characterized by Brunauer-Emmett-Teller method, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), and also photoluminescence (PL) emission spectroscopy. The photocatalytic activity of Ce3+–TiO2 catalysts was evaluated in the 2-mercaptobenzothiazole (MBT) degradation in aqueous suspension under UV or visible light illumination. The experimental results demonstrated that the overall photocatalytic activity of Ce3+–TiO2 catalysts in MBT degradation was signigicantly enhanced due to higher adsorption capacity and better separation of electron-hole pairs. The experimental results verified that both the adsorption equilibrium constant (Ka) and the saturated adsorption amount (Γmax) increased with the increase of cerium ion content. The results of XPS analysis showed that the Ti3+, Ce3+, and Ce4+ ions reside in the Ce3+–TiO2 catalysts. The results of DRS analysis indicated that the Ce3+–TiO2 catalysts had significant optical absorption in the visible region between 400 and 500 nm because electrons could be excited from the valence band of TiO2 or ground state of cerium oxides to Ce 4f level. In the meantime, the dependence of the electron-hole pair separation on cerium ion content was investigated by the PL analysis. It was found that the separation efficiency of electron-hole pairs increased with the increase of cerium ion content at first and then decreased when the cerium ion content exceeded its optimal value. It is proposed that the formation of two sub-energy levels (defect level and Ce 4f level) in Ce3+–TiO2 might be a critical reason to eliminate the recombination of electron-hole pairs and to enhance the photocatalytic activity.

Effect of calcination temperature on morphology and photoelectrochemical properties of anodized titanium dioxide nanotube arrays

Abstract: Highly ordered TiO2 nanotube arrays (TNs) are prepared by electrochemical anodization of titanium foil in a mixed electrolyte solution of glycerol and NH4F and then calcined at various temperatures The prepared samples are characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy The photocatalytic activity is evaluated by photocatalytic degradation of methyl orange (MO) aqueous solution under UV light irradiation The production of hydroxyl radicals ( OH) on the surface of UV-irradiated samples is detected by a photoluminescence (PL) technique using terephthalic acid (TA) as a probe molecule The transient photocurrent response is measured by several on–off cycles of intermittent irradiation The results show that low temperatures (below 600 °C) have no great influence on surface morphology and architecture of the TNs sample and the prepared TNs can be stable up to ca 600 °C At 800 °C, the nanotube arrays are completely destroyed and only dense rutile crystallites are observed The photocatalytic activity, formation rate of hydroxyl radicals and photocurrent of the TNs increases with increasing temperatures (from 300 to 600 °C) due to the enhancement of crystallization Especially, at 600 °C, the sample shows the highest photocatalytic activity due to its bi-phase composition, good crystallization and remaining tubular structures With further increase in the calcination temperature from 600 to 800 °C, the photocatalytic activity rapidly decreases due to the vanishing of anatase phase, collapse of nanotube structures and decrease of surface areas