Synthesis and characterization of g-C3N4 / TiO2 composites for use in heterogeneous photocatalysis

Namen diplomskega dela je bila sinteza kompozitov grafitnega ogljikovega nitrida (g-C3N4) in titanovega dioksida, ki bi lahko bili učinkoviti fotokatalizatorji za uporabo v heterogeni fotokatalizi. g-C3N4 sem sintetizirala s polimerizacijo prekurzorja diciandiamida pod različnimi pogoji, kompozite pa sem nato pripravila s homogenizacijo v ahatni terilnici v masnem razmerju 1:1 g-C3N4 in komercialnega TiO2. Pripravljene kompozite sem nato karakterizirala z različnimi površinsko občutljivimi tehnikami, kot so: dušikova fizisorpcija, fotoluminiscenca, rentgenska praškovna difrakcija, elektronska spektroskopija (UV-Vis difuzna refleksija), infrardeča spektroskopija. Opravila sem tudi test aktivnosti kompozitov pod vidno svetlobo s kumarinom. Cilj je tako bila primerjava lastnosti katalizatorjev, ki so bili pripravljeni z različno končno temperaturo pri sintezi g-C3N4. Kot najbolj aktiven katalizator se je izkazal g-C3N4 600/TiO2, pri katerem je bil g-C3N4 sintetiziran s končno temperaturo 600 °C, imel je tudi najvišjo specifično površino med kompoziti. Ugotovili smo, da se kompozitom z večanjem končne temperature pri sintezi g-C3N4 povečujeta urejenost strukture in specifična površina ter da so kompoziti aktivni v vidnem spektralnem področju. Homogenizacija TiO2 in g-C3N4 v masnem razmerju 1:1 zmanjša hitrost rekombinacije nabojev in poveča aktivnost.The purpose of this thesis was to synthesize composites of graphite carbon nitride (g-C3N4) and titanium dioxide, which could be effective photocatalysts for use in heterogeneous photocatalysis. g-C3N4 was synthesized by polymerization of the dicyandiamide precursor under different conditions, and the composites were then prepared by homogenization in an agate mortar in a 1:1 weight ratio of g-C3N4 and commercial TiO2. The prepared composites were then characterised by various surface-sensitive techniques, such as: nitrogen physisorption, photoluminescence, X-ray powder analysis, electron spectroscopy (UV-Vis diffuse reflection), infrared spectroscopy and I also tested the activity of composites under visible light with coumarin. The aim was thus to compare the properties of catalysts, which were prepared with different final temperatures in the synthesis of g-C3N4. The most active catalyst proved to be g-C3N4 600 / TiO2, which contained g-C3N4 synthesized with a final temperature of 600 °C, it also had the highest specific surface area among composites. We found that composites increase the order of structure and specific surface area with increasing final temperature during g-C3N4 synthesis, and that composites are active under visible light. Homogenization of TiO2 and g-C3N4 in a weight ratio of 1:1 reduces the rate of charge recombination and increases activity