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Rate-Limiting Steps of Dye Degradation over Titania-Silica Core-Shell Photocatalysts.
- Source :
-
Catalysts (2073-4344) . Jul2019, Vol. 9 Issue 7, p583-583. 1p. - Publication Year :
- 2019
-
Abstract
- In this work, we employed a step-by-step sol-gel process to controllably deposit ultra-thin layers of Si O 2 on anatase nanoparticles in the range between 0 and 1 nm. The deposition was confirmed by TEM, EDX, and ATR-FTIR (e.g., Ti-O-Si band at 960 c m - 1 ). Zeta potential measurements unravelled a continuous change in surface charge density with increasing silica shell thickness. The photocatalysts were evaluated towards adsorption and degradation of positively-charged and negatively-charged dyes (methylene blue, methyl orange) under UV illumination. The growth mechanism follows the Stranski–Krastanov model with three thickness regimes: (a) Flat islands (first step), (b) mono/bilayers (second/third step), and (c) regular thick films (fourth/fifth step). The results suggest different rate limiting processes for these regimes: (a) For the thinnest scenario, acidic triple-phase boundaries (TPBs) increase the activity for both dyes with their accessibility being the rate limiting step; (b) for continuous mono/bilayers, dye adsorption on the negatively-charged S i O 2 shells becomes the rate liming step, which leads to a stark increase in activity for the positively-charged MB and a decrease for MO; (c) for thicker shells, the activity decreases for both dyes and is limited by the charge transport through the isolating shells. [ABSTRACT FROM AUTHOR]
- Subjects :
- *PHOTOCATALYSTS
Subjects
Details
- Language :
- English
- ISSN :
- 20734344
- Volume :
- 9
- Issue :
- 7
- Database :
- Academic Search Index
- Journal :
- Catalysts (2073-4344)
- Publication Type :
- Academic Journal
- Accession number :
- 138008642
- Full Text :
- https://doi.org/10.3390/catal9070583