Visible Light Photocatalysis via CdS/TiO2 Nanocomposite Materials
Ferreira, Fabio A. S.
Friday, 04 May 2007 22:01 UTC
Clean Energy Research Center, College of Engineering, University of South Florida, USA report:Nanostructured colloidal semiconductors with heterogeneous photocatalytic behavior have drawn considerable attention over the past few years. This is due to their large surface area, high redox potential of the photogenerated charge carriers, and selective reduction/oxidation of different classes of organic compounds. In the present paper, we have carried out a systematic synthesis of nanostructured CdS-TiO2 via reverse micelle process. The structural and microstructural characterizations of the as-prepared CdS-TiO2 nanocomposites are determined using XRD and SEM-EDS techniques. The visible light assisted photocatalytic performance is monitored by means of degradation of phenol in water suspension.
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hi can you tell me what kind of lamp you used for this experiment
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Thank you for comment Aparna,
Photocatalytic experiments using visible light and a combination of UV-A and visible light were performed using a single lamp and an annular reflector to provide irradiation. A 1000W metal halide lamp was experimentally chosen, since it adequately replicated both the pattern and intensity peaks of the solar spectrum more accurately than other visible sources such as high-pressure sodium and fluorescent lamps. -
Complementing,
Studies have proven that with the appropriate particle interaction, CdS-TiO2 nanocomposites can efficiently decompose organics such as phenol and methylene blue under visible light irradiation less than 495nm.
The reaction occurs when a CdS particle is excited by a photon with a wavelength less than 495 nm. An EHP is formed, and subsequently the photogenerated electron is quickly transferred to the conduction band of a coupled TiO2 particle that has a conduction band edge more positive than the CdS particle (∼ 0.5 eV). The photogenerated hole in the quantum-sized CdS particle can
theoretically migrate to the surface and participate in the oxidation of adsorbed organics. The electrons that are transferred to the conduction band of TiO2 have no holes to recombine with and therefore participate in reduction reactions according to the conduction band energy level of TiO2. In order to establish a quantum size effect, one must have to synthesize extremely small particles of the order of the excitonic diameter and to stabilize them against further growth. Reversemicelle process provides a controlled environment to achieve this goal. Reverse micelles are thermodynamically stable structures which consist of a nanometer-sized spherical water core that is encapsulated by surfactant molecules in a nonpolar medium.
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