Preparation, Characterization And Photocatalytic Properties Of Doped TiO₂Hollow Nanoparticles

Anionic PSt （polystyrene） latexes were synthesized using emulsion polymerization ofmethacrylic acid and styrene （St）. The anionic PSt particles were surface treated using vinyltrimethoxysilane in a mixture of ethanol and water. PSt/TiO₂composite nanoparticles withAg₂O doping were then prepared through hydrolysis of tetrabutyl titanate （TBT） and thereaction of AgNO₃with NaOH using the surface treated PSt particles as the template. Agdoped Ag-TiO₂hollow nanoparticles were successfully prepared with the PSt/TiO₂compositemicrospheres treated at180°C, dried at80°C and calcined at500°C. The morphology ofPSt/TiO₂particles, crystal structure, elementary composition and specific surface area ofAg-TiO₂hollow particles were characterized with SEM, TEM, XRD, EDS and BET.Photocatalytic activity of Ag-TiO₂hollow nanoparticles in degradation of Rhodamine B （RhB）was tested under ultraviolet light and visible light. The results showed that, under UV light,RhB degradation increased about11%when Ag-TiO₂particles with molar ratio nAg/nTiof0.1%was used as the catalyst compared with that done with pure TiO₂hollow particles; and RhBdegradation increased about30%under visible light for Ag-TiO₂composite particles with Agcontent at nAg/nTiof1.0%.In the same way, PSt/TiO₂composite nanoparticles with AgCl doping were then preparedthrough hydrolysis of TBT and the reaction of AgNO₃with NaCl using the surface treated PStparticles as the template. AgCl-TiO₂hollow nanoparticles were obtained with the PSt/TiO₂composite particles with AgCl doping pre-treated at180°C, followed by drying andcalcination at500°C for4h. XRD characterization of the final AgCl-TiO₂particles revealedthat anatase crystal structure in pure TiO₂was unchanged with AgCl doping. EDS analysisshowed that part of the added AgCl was transformed to Ag element. BET test indicated thataverage pore size in the AgCl-TiO₂porous and hollow particles was about12nm with aspecific surface varied from125m²Â·g^-1to190m²Â·g^-1, depending on the amount of AgCl used.Photocatalytic activity of the AgCl-TiO₂hollow particles in degradation of RhB was testedunder UV and visible light. The results showed that, under UV light, RhB degradation at30min increased by about13%when AgCl-TiO₂particles with AgCl content at nAg/nTi=0.1% was used compared with that done with pure TiO₂hollow particles as the catalyst; whereas anincrease of about38%was observed under visible light with AgCl-TiO₂composite particleswith AgCl content at nAg/nTi=2.0%at120min of the photodegradation. In addition, thephotocatalytic activity of the AgCl-TiO₂particles under visible light was increasing with AgClamount up to nAg/nTi=2.0%, and this catalytic activity started to decrease when AgCl amountreached nAg/nTi=4.0%. Nevertheless, all the AgCl-TiO₂particles demonstrated a higherphotocatalytic performance than the commercial TiO₂P25, regardless of their AgCl content.The mechanism of AgCl-TiO₂photocatalysis was discussed and the results were interpretedbased on the mechanism.