Preparation And Properties Of CdS/TiO₂and Cu₂O/CdS Nanocomposite Semiconductor

Semiconductor composite materials can effectively avoid the recombination ofphotoelectrons and holes, improve the separating results of charges of the system andexpand the absorption spectrum, which have become a hot research aspect ofphotoelectrocatalysis materials. CdS/TiO2composite nanoparticles were prepared by asimple chemical precipitation method. CdS/TiO2coaxial nanowire arrays andCu2O/CdS nanowire arrays were obtained using electro-deposition method withporous anodic aluminum oxide (AAO) as templates. Their structures, morphologies,optical absorption properties and photocatalytic properties were also determined.CdS/TiO2composite nanoparticles were prepared by chemical precipitationmethod. The results showed that TiO2and CdS in the composites could be indexed toan anatase phase and hexagonal crystal, respectively. The composites presented anabsorption band between400and550nm, and the absorption strength increased withthe increasing of CdS. Photocatalytic degradation of rhodamine B showed that thecomposites exhibited excellent photodegradation efficiency and reusability. Thekinetics of photocatalytic degradation experiments were belonged to first-stagereaction dynamics equation. The photocatalytic hydrogen generation showed that thecomposites had high activity of hydrogen generation and stability.TiO2nanotube arrays were firstly prepared by the combination of theelectro-deposition method and the anodic aluminum oxide (AAO) templating method,then CdS nanowires were deposited in TiO2nanotube arrays and finally CdS/TiO2coaxial nanowires electrode were obtained. SEM and TEM indicated that CdSnanowires had been deposited into the TiO2nanotubes, which showed coaxialnanowires structure; the external diameter of coaxial nanowires was about100nm,wall thickness was about25nm and the diameter of the CdS nanowires was about50nm. The Mott-Schottky curves indicated that CdS nanowires and TiO2nanotubes wereall n-type semiconductors. The absorption edge of composites showed an obviousred-shift and absorption peak was appeared in the visible light region. Photoelectricperformance test showed that, comparing with the TiO2nanotube arrays, the opencircuit potential of CdS/TiO2coaxial nanowires reached the maximum. Degradationtest showed that the degradation efficiency of rhodamine B was improvedsignificantly under photocatalysis and photoelectrocatalysis conditions, and itsphotoelectrocatalysis degradation efficiency reached93.53%after4hours. Cu2O/CdS nanowires were obtained using electro-deposition method with AAOas templates. The optimal preparation technology was as follows: depositiontemperature of Cu2O was55℃, pH of Cu2O solutions was10, deposition charge ofCu2O was1C, deposition temperature of CdS was50℃and deposition charge of CdSwas3C. Comparing with CdS nanowires, the absorption edge of composites showedan obvious red-shift. Cu2O/CdS nanowires array electrodes showed higherphotocatalysis and photoelectrocatalysis performance than CdS nanowires and Cu2Onanowires array electrodes in the rhodamine B solutions, and the stability was good.The Mott-Schottky curve indicated that Cu2O nanowire was a p-type semiconductor.