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Synthesis Of CdS/TiO2 Nanotubes And Photocatalytic Performance Of Splitting Water Into Hydrogen

Posted on:2012-08-11Degree:MasterType:Thesis
Country:ChinaCandidate:J ShenFull Text:PDF
GTID:2131330335454478Subject:Inorganic Chemistry
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In this paper, the CdS powder with different phases,TiO2 nanotubes and Pt-CdS-TiO2NTs composites were prepared. The samples were characterized by XRD,TEM and UV-vis diffuse reflectance spectroscopy.As well as their photocatalytic performance was evaluated by water splitting into hydrogen. The research was mainly composed of three parts:(1)CdS powder with different phases were synthesized by precipitation and heated at 400℃,500℃,600℃respectively. Their photocatalytic activity for water splitting into hydrogen was investigated under visible light irradiation (λ>400nm).The influence of crystal structure of CdS, sacrificial reagents and the loading amount of cocatalyst (Pt) on the photocatalytic activity was examined. The results indicated that CdS with mixed phases (cubic and hexagonal) calcined at 400℃presented the best photocatalytic activity.Using lactic acid as sacrificial reagent was more advantageous to water splitting into hydrogen than using Na2S and Na2SO3 solution. CdS loaded 0.1 wt% Pt showed the highest photocatalytic activity, the amount of evolved hydrogen was totalled up to 5.7mL after 5h.(2) The TiO2 nanotubes were prepared by the hydrothermal method. Its photocatalytic activity for water splitting was investigated by photocatalytic reaction using methanol as sacrificial reagent under UV light irradiation. The results indicated that the amount of evolved hydrogen reached the maximum when Pt-loading amount is 0.1wt%.The amount of evolved hydrogen was totalled to 3.6mL after 5h. But the photocatalytic activity reduced when the amount of Pt increased, because excessive Pt resulted in the agglomeration of Pt nanoparticles on the TiO2NTs surface, which reduced the photocatalytic activity of TiO2NTs.(3) Pt-CdS-TiO2NTs composites were prepared by ion-exchange, photodeposition and grinding method. The photocatalytic activity for hydrogen production was investigated in aqueous Na2S and Na2SO3 solution under visible light irradiation(λ>400nm). The influence of Pt-loading amount and location on photocatalytic activity was studied. Moreover, reaction mechanism was also researched. The results indicated that the photocatalytic activity of Pt-TiO2NTs/CdS was higher than Pt-(TiO2NTs/CdS) and Pt-CdS/TiO2NTs when the Pt-loading amount was 0.1 wt%.In the case of Pt-TiO2NTs/CdS,we speculated the electron transfer had followed the sequence of CdS→TiO2→Pt, which improved the performance of photocatalyst for water splitting into hydrogen. When the amount of Pt was 0.4wt%, Pt-(CdS/TiO2NTs) presented the highest photocatalytic activity.CdS/TiO2NTs composite exhibited high visible light photocatalytic activity because it could improve the transfer of electrons and separate the combination of holes and charges.Pt-CdS/TiO2NTs produced the least amount of hydrogen after 5h.Pt loading on the surface of CdS limited the transfer of electrons, which in turn became the center of combination of holes and electrons, resulting in the decrease of photocatalytic activity.
Keywords/Search Tags:Photocatalysis, Hydrogen production, CdS, TiO2NTs, Cocatalyst (Pt)
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