Improved photocatalytic activity of SnO$_2$-TiO$_2$ nanocomposite thin films prepared by low-temperature sol-gel method

Maver, Ksenija (author), Arčon, Iztok (author), Fanetti, Mattia (author), Al Jitan, Samar (author), Palmisano, Giovanni (author), Valant, Matjaž (author), Lavrenčič Štangar, Urška (author)

The objective of this research was to investigate how the photocatalytic activity of pure TiO$_2$ can be improved by SnO$_2$ modification. Different molar ratios of tin to titanium were prepared. The correlation between tin concentration and structural properties was investigated to explain the mechanism of photocatalytic efficiency and to optimize the synthesis conditions to obtain enhanced activity of the SnO$_2$-modified TiO$_2$ photocatalysts under UV-irradiation. The SnO$_2$-modified TiO$_2$ photocatalysts were prepared by a low-temperature sol-gel method based on organic tin and titanium precursors. The precursors underwent sol-gel reactions separately to form SnO$_2$-TiO$_2$ sol. The sol-gels were deposited on a glass substrate by a dip-coating technique and dried at 150 °C to obtain the photocatalysts in the form of a thin film. To test the thermal stability of the material, an additional set of photocatalysts was prepared by calcining the dried samples in air at 500 °C. The photocatalytic activity of the samples was determined by measuring the degradation rate of an azo dye. An increase of up to 30% in the photocatalytic activity of the air-dried samples was obtained when the TiO$_2$ was modified with the SnO$_2$ in a concentration range of 0.1–1 mol.%. At higher SnO$_2$ loadings, the photocatalytic activity of the photocatalyst was reduced compared to the unmodified TiO$_2$. The calcined samples showed an overall reduced photocatalytic activity compared to the air-dried samples. Various characterization techniques (UV-Vis, XRD, N$_2$-physisorption, TEM, EDX, SEM, XAS and photoelectrochemical characterization) were used to explain the mechanism for the enhanced and hindered photocatalytic performances of the SnO$_2$-modified TiO$_2$ photocatalysts. The results showed that the nanocrystalline cassiterite SnO$_2$ is attached to the TiO$_2$ nanocrystallites through the Sn-O-Ti bonds. In this way, the coupling of two semiconductors, SnO$_2$ and TiO$_2$, was demonstrated. Compared to single-phase photocatalysts, the coupling of semiconductors has a beneficial effect on the separation of charge carriers, which prolongs their lifetime for accessibility to participate in the redox reactions. The maximum increase in activity of the thin films was achieved in the low concentration range (0.1–1 mol.%), which means that an optimal ratio and contact of the two phases is achieved for the given physical parameters such as particle size, shape and specific surface area of the catalyst.

• Language: English
• Keywords: photocatalytic activity, SnO$_2$-modified TiO$_2$, low-temperature, thin films, XAS analysis, Sn-modified TiO$_2$
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Publication status: Published
• Publication version: Version of Record
• Year: 2021
• Number of pages: Str. 540–549
• Numbering: Vol. 397–399
• PID: 20.500.12556/RUL-138674
• UDC: 54
• ISSN on article: 0920-5861
• DOI: 10.1016/j.cattod.2021.06.018
• COBISS.SI-ID: 69207043
• Publication date in RUL: 09.08.2022

Record is a part of a journal

• Title: Catalysis today
• Shortened title: Catal. today
• Publisher: Elsevier
• ISSN: 0920-5861
• COBISS.SI-ID: 15324421

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.