Tuning the photocatalytic activity of nanocrystalline titania by phase composition control and nitrogen doping, using different sources of nitrogen

Titania nanoparticles were synthesized by employing the hydrothermal method and using TiOSO 4 as a titanium source. By varying pH between 0.5 and 1.0 and adding isopropanol to the hydrothermal reaction mixture, different mixtures ofanata- se, rutile, and brookite were obtained. The samples were also doped with nitrogen at different N concentrations using, res- pectively, urea, ammonium nitrate, and tripropylamine as nitrogen sources. The samples were characterized by X-ray pow- der diffraction, field emission scanning electron microscopy, infrared spectroscopy, UV-Vis diffuse reflectance spectros- copy and according to their specific surface area. Additionally, their photocatalytic activity was measured in a gas-solid reactor system. The results show that low pH favours rutile formation, whereas a higher pH yields mixed phase titania poly- morphs. Isopropanol addition also favours rutile formation, and boosted the photocatalytic activity of the resulted particles. Contrary to most data in the literature, rutile turned out to be the more active phase in the present investigation. Nitrogen doping, on the other hand,did not contribute to higher photocatalytic activity, but was rather detrimental to it. S hidrotermalno metodo smo sintetizirali nanodelce titanovega oksida. Kot izvor titana smo uporabili TiOSO4. Spreminjali smo pH med 0,5 in 1,0 ter dodatek izopropanola v reakcijsko zmes in s tem pripravili različne zmesi anataza, rutila in brookita. Vzorce smo tudi dopirali z različnimi deleži dušika, pri čemer smo kot izvor dušika uporabili sečnino, amonijev nitrat in tripropilamin. Vzorce smo karakterizirali z rentgensko praškovno difrakcijo, elektronsko vrstično mikroskopijo na poljsko emisijo, infrardečo spektroskopijo, UV-Vis difuzno refleksijsko spektroskopijo in jim določali specifično površino. Fotokatalitsko aktivnost pa smo merili v reaktoskem sistemu plin-trdno. Ugotovili smo, da nizek pH favorizira nastajanje rutila, medtem ko višje vrednosti pH vodijo do mešanih polimorfnih faz titanovega oksida. Tudi dodatek izopropanola pospešuje nastajanje rutila. V nasprotju z večino literaturnih podatkov je bila v naši raziskavi najbolj fotokatalitsko aktivna rutilna modifikacija. Dopiranje z dušikom pa ne poveča fotokatalitske aktivnosti, ampak jo celo nekoliko zmanjša.