Imobilizacija in karakterizacija fotokatalizatorja ter razvoj transparentnega mikrosistema za fotokatalizo

Črv, Špela (avtor), Plazl, Igor (mentor)

Heterogena fotokataliza je zanimiva napredna oksidacijska metoda, ki za delovanje uporablja fotokatalizator in svetlobo. Ko je fotokatalizator izpostavljen svetlobi primerne valovne dolžine in s tem tudi primerne energije, to energijo absorbira in jo porabi za ustvarjanje visoko reaktivnih parov elektron-vrzel. Ti pari sprožijo tvorbo reaktivnih kisikovih specij (ROS), kot so hidroksilni radikali. Najpogosteje uporabljen fotokatalizator je titanov dioksid (TiO$_2$), saj ima dobre lastnosti za fotokatalizo, kot so dobra fotokatalitska stabilnost in visok fotokatalitski odziv, prav tako je relativno poceni material. Glavna pomanjkljivost, ki preprečuje široko uporabo heterogene fotokatalize, je njena potreba po praškastih fotokatalizatorjih, ki pa jih je po reakciji težko reciklirati. Tej težavi se lahko izognemo z imobilizacijo fotokatalizatorja na nosilec. V magistrskem delu smo razvili metodo za imobilizacijo komercialnega TiO$_2$ na steklen substrat (objektno stekelce) s pomočjo imobilizacije z vrtenjem (angl. spin coating), pri čemer je bila povprečna masa nanosa fotokatalizatorja 14,4 mg. Za izboljšanje mehanskih lastnosti smo dodali tetraetilortosilikat (TEOS). Aktivnost fotokatalizatorja smo najprej preverjali v šaržnem sistemu, ki je bil osvetljevan z UV-svetlobo, preko hitrosti tvorbe hidroksilnih radikalov. Opazili smo, da se aktivnost prvih 24 h osvetljevanja povečuje, nato pa se ustali. Fotokatalizator smo karakterizirali z različnimi tehnikami: FTIR-ATR, XRD, PL, UV-Vis DR, CHNS-analiza, SEM-EDX in profilometrijo. Pokazali smo, da je imobiliziran material ohranil anatazno obliko TiO$_2$, da je silicij prisoten v obliki SiO$_2$, da so elementi Ti, Si in O enakomerno porazdeljeni po materialu in da material ne vsebuje organskih spojin. Ugotovili smo tudi, da predhodno osvetljevanje ne vpliva na hitrost rekombinacije materiala in na širino prepovedanega pasu. S časom osvetljevanja se povečuje le hrapavost materiala in s tem njegova aktivna površina, kar pojasni povečanje aktivnosti. V mikropretočnem reaktorju smo opazovali hitrost tvorbe hidroksilnih radikalov in razvili matematični model za opis hitrostnega in koncentracijskega profila v mikroreaktorskem kanalu. Model smo uporabili za analizo eksperimentalnih podatkov, vendar ga nismo validirali.

• Jezik: Slovenski jezik
• Ključne besede: Heterogena fotokataliza, TiO$_2$, imobilizacija z vrtenjem, mikroreaktorski sistem, OH· radikali.
• Vrsta gradiva: Magistrsko delo/naloga
• Tipologija: 2.09 - Magistrsko delo
• Organizacija: FKKT - Fakulteta za kemijo in kemijsko tehnologijo
• Leto izida: 2025
• PID: 20.500.12556/RUL-167926
• COBISS.SI-ID: 229714179
• Datum objave v RUL: 20.03.2025

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Photocatalyst immobilization and characterization and development of a transparent microsystem for photocatalysis

Izvleček

Heterogeneous photocatalysis is an advanced oxidation process that utilizes a photocatalyst and light to drive reactions. When exposed to light of the appropriate wavelength and energy, the photocatalyst absorbs this energy and generates highly reactive electron-hole pairs. These pairs initiate the formation of reactive oxygen species (ROS), such as hydroxyl radicals. Titanium dioxide (TiO$_2$) is the most commonly used photocatalyst due to its advantageous properties for photocatalysis, including good photocatalytic stability, high reactivity, and relative cost-effectiveness. However, the need for powdered photocatalysts with a large specific surface area limits the widespread application of heterogeneous photocatalysis. The use of such materials presents challenges, including the separation of the photocatalyst after the reaction and aggregation at higher concentrations. These issues can be addressed by immobilizing the photocatalyst onto a support. In this thesis, we developed a method for immobilizing commercial TiO$_2$ onto a glass substrate (microscope slide) using spin coating, achieving an average deposition of 14.4 mg. To enhance the mechanical properties of the immobilized photocatalyst, TEOS was added. The photocatalytic activity was first tested in a batch system illuminated by UV light by measuring the rate of hydroxyl radical formation. We observed that the activity increased during the first 24 hours of illumination and then stabilized. The photocatalyst was characterized using various techniques, including FTIR-ATR, XRD, PL, UV-Vis DR, CHNS analysis, SEM-EDX, and profilometry. The results demonstrated that the immobilized material retained the anatase form of TiO$_2$, that silicon was present as SiO$_2$, and that elements Ti, Si and O were uniformly distributed across the material, which was free of organic compounds. Pre-illumination did not significantly impact charge recombination rates or the band gap width. The roughness of the material, and thus its active surface area, increased with illumination time, explaining the enhanced activity. In a microfluidic reactor, we observed the rate of hydroxyl radical formation and developed a mathematical model to describe the velocity and concentration profiles within the microreactor channel. This model was used to analyze experimental data, but it has not yet been validated.

• Ključne besede: Heterogeneous photocatalysis, TiO$_2$, immobilization, microreactor, spin coating, OH· radicals