| Semiconductor photocatalysis, a green methodology, is not only used in H2 production with solar energy, but also applied in organic pollutants degradation. It has attracted tremendous attentions in energy and environmental fields. Among the semiconductors, highly ordered TiO2 nanotube arrays （TNTAs） are widely considered as one of the most promising and versatile materials. TNTAs has some advantages including high surface-to-volume ratios, high adsorption capacity and uniformly ordered structure. However, TNTAs has the intrinsic drawbacks of poor visible-light absorption and fast charge carrier （electron-hole） recombination which hinder its practical application.Therefore, in this paper, TNTAs was used as the substrate to be modified with CdS and Pt quantum dots, then Pt-TNTAs, CdS-TNTAs and Pt/CdS-TNTAs were prepared. The composition, morphology and optical property of the catalysts were characterized by the X-ray diffraction （XRD）, Raman spectroscopy, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray photoelectron spectroscopy （XPS）, and UV-vis absorption spectra. The photocatalytic performances of the nanomaterials were evaluated by Rhodamine B （Rh B） degradation and hydrogen generation from suspended photocatalytic systems. The detailed works are summarized as follows:（1） TNTAs were prepared by electrochemical anodization in ethylene glycol, DMSO, glycerol and （NH4）2SO4 solutions, respectively. Among them, the formed nanotubes in glycerol solutions were top-open, orderd regularly and well adhered to the Ti substrate. The UV-light photocatalytic tests showed that the photocatalytic activities on TNTAs in different solutions is glycol> DMSO> glycerol> （NH）2SO4 indicating that the activity was extensively affected by the length of tubes. For TNTAs made in glycol and DMSO solutions, the formation of needle-or grass-like morphologies at the tube tops can be observed and collapsing tube tops were not of benefit to the modification with nanoparticles. Therefore, TNTAs made in glycerol solution were used as the substrate for the next study.（2） Through a modified two-step photo irradiation-reduction method, Pt-TNTAs nanocomposite was prepared by depositing Pt QDs on the nanochannels of TNTAs. The effect of different concentration of precusor solution on the amount of Pt deposits was studied. The decreasing the concentration of precursor （2.0 mM to 0.3 mM） resulted in more Pt QDs aggregation. The UV-light photocatalytic tests suggested that compared with Pt（1.0）-TNTAs and Pt（2.0）-TNTAs, Pt（0.3）-TNTAs exihibited highest photocalytic activity and the degradating rate of Pt（0.3）-TNTAs was about 3.3 times than that of TNTAs. The EPR spin-trap technique demonstrated that both·OH and O2-radicals were generated and involved during the degradation process.（3） Through a modified successive ionic layer adsorption and reaction （SILAR） method, CdS-TNTAs nanocomposite was fabricated by depositing CdS QDs on nanochannels of TNTAs.The UV-vis diffuse reflection spectra showed that CdS-TNTAs possessed more intensive absorption within the visible light range owing to the synergistic effect. CdS（15）-TNTAs with proper amount of well dispersed CdS QDs had superior photocatalytic activity in visible-light-induced H2 production and Rh B degradation than other catalysts.（4） Pt/CdS-TNTAs were prepared by simply depositing Pt and CdS QDs on the surface of TNTAs in sequence. Pt QDs about 3 nm and CdS QDs about 7 nm accumulate into the triangle form together with the TNTAs substrate. The resulting Pt/CdS-TNTAs had a strong visible-light response and presented synergetic effects and obvious electron interaction among the three components. The superoxide and hydroxyl radicals were both responsible for the visible-light degradation of Rh B, which were also confirmed by EPR analysis. The prepared samples were easy to be recycled after the catalytic process and had high stability compared with powder catalysts. The prepared photocatalyst may have potential applications in environmental or other fields. |
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