Science in China: Series B Chemistry 2006 Vol.49 No.1 67—74 67
Sunlight-activated AlFeO3/TiO2 photocatalyst
YUAN Zhihao, WANG Yuhong, SUN Yongchang, WANG Jing, BIE Lijian & DUAN Yueqing
Nanomaterials & Nanotechnology Research Center, School of Materials Science & Engineering, Tianjin University of Technol-ogy, Tianjin 300191, China
Correspondence should be addressed to Yuan Zhihao (email: zhyuan@http://www.wendangxiazai.com or zhyuan@http://www.wendangxiazai.com)
Received December 10, 2004; accepted April 13, 2005
Abstract A nanocomposite photocatalyst composed of AlFeO3 and TiO2 is prepared, and charac-terized through X-ray diffraction. Application of the nanocomposite for the photodegradations of eosin dye and methyl orange gives an improved photoactivity compared with TiO2-only nanomaterials. The optimal concentration of AlFeO3 in the composite is about 1.0 wt% under UV excitation, and 9.0 wt% under sunlight excitation for the improved photoactivity. Furthermore, this nanocomposite is more active for eosin photodegradation if natural sunlight rather than UV is used. This may be due to the reason that adding AlFeO3 nanoparticles into TiO2 matrix can promote the separation of photogener-ated charge carriers, and extend the photoresponse of TiO2 toward visible region, which results in an increase in the solar energy utilization efficiency.
Keywords: nanocomposite, photocatalysis, titania, aluminum ferrite.
The photocatalytic oxidation of organic contami-nants (i.e. aromatic hydrocarbons, chlorinated aromat-ics, surfactants and pesticides, etc.) by using TiO2- based semiconductors as photocatalysts in the pres-ence of ultraviolet (UV) or natural sunlight illumina-tion has been extensively studied in the past decades owing to its excellent (photo)chemical stability, low
cost and non-toxicity. However, the technological
application is limited by several factors, the most restrictive one is the large band-gap energy of TiO2 (anatase 3.2 eV, rutile 3.0 eV), and thus the excitation
with wavelength below 400 nm is necessary. To develop highly active photocatalyst under visible light appears to be an appealing challenge.
Great efforts have been made to extend the wave-length range of photoactivity by using organic dye
sensitization or doping with transition metal
ions[5,9,15] in TiO2 matrix, but most of the work is un-―
successful[6,13,1517]. A coupled semiconductor system has also aroused some interest. Composed of TiO2 and another semiconductor with relatively small band-gap (i.e. CdS, CdSe, FeS2, RuS2), this system can extend the photoresponse of TiO2 into visible range, and thus largely increase the solar energy utilization effi-―
ciency. Unfortunately, these sulfides and se-lenides are both sensitive to photoanodic corrosion. Recently, several inorganic semiconductors (i.e. ZnFe2O4, MgFe2O4) with relatively small band-gaps have attracted attentions in photoelectric conversion and photochemical hydrogen production from water due to their utilizing visible light and good photo-―
chemical stability. A nanocomposite composed of ferrites and TiO2 might exhibit some useful charac-teristics of suitable applications in photocatalysis and