Tailored Anatase/Brookite Nanocrystalline TiO2. The Optimal Particle Features for Liquid- and Gas-Phase Photocatalytic Reactions
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- 作者：Silvia Ardizzone ; Claudia L. Bianchi ; Giuseppe Cappelletti ; Stefano Gialanella ; Carlo Pirola ; Vittorio Ragaini
- 刊名：Journal of Physical Chemistry C
- 出版年：2007
- 出版时间：September 6, 2007
- 年：2007
- 卷：111
- 期：35
- 页码：13222 - 13231
- 全文大小：830K
- 年卷期：v.111,no.35(September 6, 2007)
- ISSN：1932-7455
文摘
Anatase-brookite composite nanocrystals were synthesized successfully by a controlled sol-gel reactionfollowed by a prolonged hydrothermal aging or by mild calcinations (300 and 450 
C). The physicochemicaland photocatalytic properties of the synthesized TiO2 composites were studied along with several commerciallyavailable nanocrystalline TiO2 samples showing different features. Rietveld refinements of the powder X-raydiffraction pattern were used to track the brookite content systematically and to generally assess the phasecomposition of the different samples and their crystallite sizes. SEM, TEM, and HRTEM were used tocharacterize the particle morphology, size, and surface faceting. BET/BJH analyses combined with mercuryporosimetry determinations were employed to characterize the surface area, porosity, and pore size distribution.The surface state of the TiO2 samples was analyzed by XPS by studying, in detail, the region of oxygen 1sto produce the OH/Otot surface ratio. The photocatalytic activity of all of the samples was tested both fordegradation of NOx in the gas phase and for the oxidation of 2-chlorophenol in the liquid phase. The differentsamples showed the same sequence of activity for the two reactions. The highest degradation and mineralizationefficiencies were achieved in the case of samples showing smaller crystallite sizes and larger surface areas.The photocatalytic activity of the anatase-brookite composite, submitted to the hydrothermal treatment, wasfound to be the highest for both reactions, even greater than that of a single-phase anatase sample showinga much-larger surface area. The different contributions to the photocatalytic performance of the TiO2nanocrystals are critically discussed.
C). The physicochemicaland photocatalytic properties of the synthesized TiO2 composites were studied along with several commerciallyavailable nanocrystalline TiO2 samples showing different features. Rietveld refinements of the powder X-raydiffraction pattern were used to track the brookite content systematically and to generally assess the phasecomposition of the different samples and their crystallite sizes. SEM, TEM, and HRTEM were used tocharacterize the particle morphology, size, and surface faceting. BET/BJH analyses combined with mercuryporosimetry determinations were employed to characterize the surface area, porosity, and pore size distribution.The surface state of the TiO2 samples was analyzed by XPS by studying, in detail, the region of oxygen 1sto produce the OH/Otot surface ratio. The photocatalytic activity of all of the samples was tested both fordegradation of NOx in the gas phase and for the oxidation of 2-chlorophenol in the liquid phase. The differentsamples showed the same sequence of activity for the two reactions. The highest degradation and mineralizationefficiencies were achieved in the case of samples showing smaller crystallite sizes and larger surface areas.The photocatalytic activity of the anatase-brookite composite, submitted to the hydrothermal treatment, wasfound to be the highest for both reactions, even greater than that of a single-phase anatase sample showinga much-larger surface area. The different contributions to the photocatalytic performance of the TiO2nanocrystals are critically discussed.