Hydrothermai Preparation And Photocatalytic Performance Of Silver/Silver Bromide Loaded Titanium Dioxide Composite

Organic dyes, as a main harmful pollutant in waste water, produced fromindustry, agriculture and waste processes, have had a negative impact on human’shealth and the environment. As a semiconductor photocatalysis, titanium dioxide(TiO2) has drawn great attention since it is one of the most promising photocatalystsin water splitting and the mineralization of toxic organic substances by its virtue ofnontoxicity, highly chemical stability, low cost and no photocorrosion. But TiO2canonly be excited by the irradiation of UV light, which merely occupies about4%oftotal solar energy. Therefore, various modifications were carried out to manipulate itselectronic band structure to make it photoactive under visible light, includingtransition metal doping anchoring organic sensitizers, noble metal doping ornon-metal doping. However, this kind of doping often leads to very definiteimprovement on its visible light photocatalytical performance.Metal silver (Ag0) have strong visible light absorption arising from localizedsurface plasmon resonance (SPR) of noble metal nanostructure. Silver bromide (AgBr)is well known as a stable small bandgap (2.6eV) semiconductor. Hence, constructingheterostructured semiconductor system which can have visible-light response is morebeneficial to the charge transfer across semiconductor interface, superior visible lightphotocatalytical performance can be expected when combining Ag/AgBr or Ag withTiO2to form multicomponent semiconductorTypically, AgNO3and CTAB were used to prepare AgBr nanoparticles on thematrix, and then Ag-AgBr could be obtained after light irradiation. CTAB played animportant role in controlling the size of the deposited nanoparticles as both Br sourceand surfactant. In the meanwhile, CTAB is known as an effective absorbance fororganic dyes. The residual CTAB from the preparation step would definitely influencethe evaluation of photodegradation activity and lead to obscure acquaintance.Nevertheless, such effect of CTAB were not made clear in the reported work.Besides, the effects of the loaded Ag-AgBr content on photocatalytic ability iscomparatively less discussed but essential for understanding the intrinsic nature of photocatalysis.In this work, a three-dimentional nanoporous TiO2hierarchical spheres with highspecific surface area was carefully chosen as a template for deposition of Ag-AgBrnanoparticles through a CTAB-assisted deposition-precipitation procedure. Weparticularly unclosed the adsorption effect of CTAB by comparing the catalyst beforeand after the calcination treatment. The photocatalytic activity of the as-preparedAg-AgBr/TiO2nanoheterostructured composites were then evaluated by degradingMethyl Orange (MO) under visible light irradiation. Ag-AgBr/TiO2or Ag-/TiO2displayed much better photocatalytic activity than pure TiO2. The different photoactivities ofvarious loaded content of Ag-AgBr and the cycling life of the photocatalyst were alsostudied. Moreover, the as-prepared Ag-AgBr/TiO2composites exhibited good stability.The photocatalytic degradation efficiency after5recycles kept at80%of the first timeactivity.