Sinteza in karakterizacija fotokatalitsko aktivnega mezoporoznega TiO$_2$ z dodatkom CeO$_2$

Knap, Mateja (author), Lavrenčič Štangar, Urška (mentor), Nadrah, Peter (comentor)

Voda in zrak sta ključnega pomena za življenje – njuno onesnaženje predstavlja velik problem za človeštvo. Za reševanje okoljske in energetske problematike v prihodnosti je ključna učinkovita uporaba sončne energije, ki je brezplačen, trajnosten vir energije, ki ga imamo v izobilju. Fotokatalizatorji so snovi, ki z uporabo sončne energije pospešijo najrazličnejše reakcije, med drugim pridobivanje energijsko bogatejših produktov in reakcije razgradnje organskih onesnaževal (do CO$_2$ in H$_2$O). Najpogosteje uporabljen fotokatalizator je titanov dioksid (TiO$_2$), vendar je njegova fotokatalitska aktivnost omejena z visoko stopnjo rekombinacije parov elektron-vrzel in relativno širokim prepovedanim pasom (3,2 eV za anatas) ter posledično nizko absorpcijo vidne svetlobe. Fotokatalitsko aktivnost lahko izboljšamo s sklopitvijo TiO$_2$ z drugim polprevodnikom – na primer s cerijevim dioksidom (CeO$_2$). V okviru magistrskega dela sem vzpostavila postopek za sol-gel sintezo z metodo samourejanja z izparevanjem (ang. evaporation-induced self-assembly, EISA) v kontroliranih pogojih pri 40 °C in 33 % relativni vlagi s sledečo kalcinacijo. Sintetizirala sem mezoporozni TiO$_2$, CeO$_2$ ter kompozite TiO$_2$-CeO$_2$. Kot prekurzor TiO$_2$ je bil uporabljen titanov(IV) butoksid, mezoporozno strukturo pa sem dosegla z dodatkom kopolimera Pluronic F127. Kompoziti TiO$_2$-CeO$_2$ so bili pripravljeni z različnimi količinami dodanega vira cerija in na različne načine glede na dodani vir cerija: 1) cerijeva sol kot prekurzor CeO$_2$, 2) predhodno sintetiziran CeO$_2$ in 3) fizikalne mešanice predhodno sintetiziranih TiO$_2$ in CeO$_2$. Fotokatalitsko aktivnost materialov sem določila s spremljanjem pretvorbe izopropanola v aceton s FTIR spektroskopijo v reaktorskem sistemu plin-trdno pri osvetljevanju z UV in vidno svetlobo, poleg tega pa še z razgradnjo barvila metilensko modro v sistemu tekoče-trdno. Sintetizirani materiali so imeli povprečni premer por 5–7 nm in visoko specifično površino. Ugotovila sem, da imata količina vira cerija in predvsem način sinteze velik vpliv na fotokatalitsko aktivnost. Najbolj aktivne so bile fizikalne mešanice, ki so v sistemu plin-trdno presegle aktivnost komercialnega TiO$_2$ P25 pri vseh količinah dodanega vira cerija.

• Language: Slovenian
• Keywords: fotokataliza, EISA, TiO$_2$, CeO$_2$, kompoziti
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2024
• PID: 20.500.12556/RUL-154169
• COBISS.SI-ID: 183334403
• Publication date in RUL: 29.01.2024

KNAP, Mateja, 2024, Sinteza in karakterizacija fotokatalitsko aktivnega mezoporoznega TiO$_2$ z dodatkom CeO$_2$ [online]. Master’s thesis. [Accessed 17 March 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=154169

Secondary language

• Language: English
• Title: Synthesis and characterization of photocatalytic mesoporous TiO$_2$ with addition of CeO$_2$

Abstract

Water and air are vital for life – their pollution presents a big problem for humanity. The key to solving environmental and energy problems in the future is an efficient use of solar energy, which is a free, sustainable, and abundant source of energy. Photocatalysts are compounds that accelerate a wide variety of reactions using solar energy, including the production of added-value products and the decomposition of organic pollutants (to CO$_2$ and H$_2$O). The most researched photocatalyst is titanium dioxide (TiO$_2$), but its photocatalytic activity is limited by a high recombination rate of electron-hole pairs and a relatively wide band gap (3.2 eV for anatase), hindering the absorption of visible light. The photocatalytic activity can be improved by coupling TiO$_2$ with another semiconductor – for example cerium dioxide (CeO$_2$). In the master's thesis, a procedure for sol-gel synthesis via the evaporation-induced self-assembly (EISA) method was established with controlled conditions (40 °C and 33 % relative humidity), followed by calcination. Mesoporous TiO$_2$, CeO$_2$ and TiO$_2$-CeO$_2$ composites were synthesized. Titanium(IV) butoxide was used as a TiO$_2$ precursor, and the mesoporous structure was achieved with the addition of the structure-directing agent Pluronic F127. TiO$_2$-CeO$_2$ composites were prepared with different amounts of cerium source using different approaches depending on the cerium source added: 1) cerium salts as CeO$_2$ precursors, 2) previously-synthesized CeO$_2$, and 3) a physical mixture of pre-synthesized TiO$_2$ and CeO$_2$. The photocatalytic activity of the materials was determined by monitoring the conversion of isopropanol to acetone with an FTIR spectroscopy in a gas-solid reactor system under UV and visible light illumination, and by the decomposition of the methylene blue dye in a liquid-solid system. The synthesized materials featured an average pore diameter of 5–7 nm and a high specific surface area. The photocatalytic activity was greatly influenced by the amount of the cerium source and especially by the synthesis approach. The physical mixtures were the most active, surpassing the activity of commercial TiO$_2$ P25 in the gas-solid system at all amounts of added cerium source.

• Keywords: photocatalysis, EISA, TiO$_2$, CeO$_2$, composites