Composites For Photocatalytic Applications Research Articles

Obtaining and Characterization of TiO2-GO Composites for Photocatalytic Applications

Titanium dioxide (TD) and graphene oxide (GO) were synthesized by sol-gel and improved Hummers method, respectively. This study shows the results of the incorporation through four different conditions (sol-gel, sol-gel and ultrasonic, annealed, and UV radiation, C1 to C4, respectively). It was observed that a homogeneous incorporation of TD on sheets of GO was obtained satisfactorily. The composites of TiO2/GO were characterized using different techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and infrared spectroscopy (IR). The photocatalytic activity of the composites was determined from the degradation of the dye azo tartrazine using UV and solar radiation. The best incorporation of TD nanoparticles on GO was obtained with condition C3 (thermal incorporation method) at a temperature of 65°C. This shows a uniformity in the size and shape of the TD as well as an excellent adherence to the sheet of GO. This addition is accomplished by ionic bonding in the presence of electrostatic Coulomb forces. The C3 composite degraded the tartrazine dye using UV radiation and sunlight. With the latter, the degradation time was three times faster than using UV light.

One-pot electrodeposition synthesis of Bi2WO6/graphene composites for photocatalytic applications under visible light irradiation

Bi2WO6 and Bi2WO6/graphene particles were synthesized by electrodeposition. The concentration of graphene in Bi2WO6/graphene composites was controlled. The impact of graphene concentration on particle morphology and surface area was investigated. The X-ray diffraction patterns indicated the crystal structures of the as-synthesized particles. The photocatalytic performance of both Bi2WO6 and Bi2WO6/graphene particles was investigated by degrading methylene blue in aqueous solution under visible light irradiation. The results showed that at medium concentration of graphene, the photocatalytic performance was the best, which could be attributed to the increased electron/hole separation during the photocatalysis. A further increased concentration of graphene decreased the photocatalytic performance of Bi2WO6/graphene, which could be attributed to its prevention of the irradiation reaching the surface of Bi2WO6.

Tailoring the porosity of ZnO/ZnFe2O4 composites for photocatalytic applications

Abstract This paper reported a novel method to synthesize porous ZnO/ZnFe 2 O 4 particles by chemically etching ZnO/ZnO 2 O 4 /SO 2 composite particles in an alkaline solution, and the porosity of the particles could be tailored by controlling the concentration of SO 2 in the ZnO/ZnO 2 O 4 /SO 2 composites. The photocatalytic performance of both solid and porous ZnO/ZnFe 2 O 4 particles was investigated in methylene blue (MB) degradation reaction. The results showed that the particles with higher porosity displayed a higher catalytic performance, which was indicated by a larger first-order reaction constant (κ) and an improved degradation efficiency (η). Moreover, the magnetization of the particles could be used for the magnetic separation of catalysts after reactions.

Aligned macroporous TiO2/chitosan/reduced graphene oxide (rGO) composites for photocatalytic applications

Abstract In this article ice templating is used to fabricate novel TiO2/chitosan/reduced graphene oxide (rGO) composites with a highly aligned macroporous structure for photocatalytic applications. The structure of the composites was readily tailored using the composite composition, for example the lamellar pore width decreased from 50–45 to 5–10 μm, while the lamellar thickness increased from 2–3 to 20–25 μm, with an increase of the TiO2 content from 45 to 77 vol%. Lamellar pore channels between the layers exhibited a more uniform distribution when the rGO content was 1.0 wt%. The increase in viscosity of the composites with high TiO2 contents led to the formation of smaller ice crystals and smaller lamellar pore sizes to enable the production of composite structures with improved mechanical strength. The TiO2/chitosan/rGO composites exhibited excellent photocatalytic degradation of methyl orange and the photocatalytic efficiency was optimized by control of the active material content and microstructure. The hybrid composites with 1.0 wt% rGO showed a degradation percentage of 97%, which makes these novel TiO2/chitosan/rGO freeze cast structures attractive materials as high performance and high strength substrates for photocatalytic degradation applications.

Influence of heat treatment on thermally-reduced graphene oxide/TiO2 composites for photocatalytic applications

Thermally-reduced graphene oxide/TiO2 composites (TRGO/Ti) were prepared by the thermal reduction of graphene oxide/TiO2 composite that was obtained from a simple, environmentally friendly, one-step colloidal blending method. The changes in structural and textural properties as well as their corresponding photocatalytic activities were investigated as a function of calcination temperature. The presence of stacked TRGO sheets significantly retarded both the aggregation and the crystalline phase transformation of TiO2 as increasing the temperature from 200 to 600 °C. TRGO/Ti composites exhibited higher photocatalytic activity for the degradation of methylene blue in comparison with pure TiO2 due to the increase in specific surface area and the formation of π-π conjugations between dye compounds and aromatic regions of TRGO. However, increasing the calcination temperature resulted in the lower photoactivity and slower kinetics, which can be ascribed to the decrease in surface area, the reduction of oxygen vacancies, and the loss of functional groups at the edges or on the basal planes of the TRGO sheets.