Zeolite-decorated black TiO<inf>x</inf> quantum dots for photocatalytic degradation of organic cationic dyes under LED light irradiation
Issued Date
2024-12-15
Resource Type
ISSN
09258388
Scopus ID
2-s2.0-85205306074
Journal Title
Journal of Alloys and Compounds
Volume
1008
Rights Holder(s)
SCOPUS
Bibliographic Citation
Journal of Alloys and Compounds Vol.1008 (2024)
Suggested Citation
Pour M.R., Fereidooni M., Praserthdam S., Praserthdam P., Marquez V., Uesaka K., Yamakata A., Paz C.V., kamjam N., kanjanaboos P. Zeolite-decorated black TiO<inf>x</inf> quantum dots for photocatalytic degradation of organic cationic dyes under LED light irradiation. Journal of Alloys and Compounds Vol.1008 (2024). doi:10.1016/j.jallcom.2024.176797 Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/101515
Title
Zeolite-decorated black TiO<inf>x</inf> quantum dots for photocatalytic degradation of organic cationic dyes under LED light irradiation
Author's Affiliation
Corresponding Author(s)
Other Contributor(s)
Abstract
Defect engineering is a promising strategy to reduce the band gap of semiconductors, enhancing their photocatalytic activity under visible light by introducing intra-bandgap energy states. Among the materials studied, oxygen-deficient black TiOx stands out due to its potential in photocatalytic reduction and hydrogen evolution. However, the valence band edge maximum (VBM) of TiOx is not thermodynamically favorable for the direct oxidation of water to hydroxyl radicals (H2O/•OH). Although the formation of extensive oxygen vacancies is necessary to extend the light absorption of black TiOx to longer wavelengths, a high density of oxygen vacancies (Ov) significantly shortens the diffusion length of charge carriers within the TiOx, leading to increased recombination of electrons and holes (e-/h+), thereby suppressing photocatalytic activity. To overcome these limitations, confining TiOx particles to the quantum dot (QD) size range and constructing heterojunctions with a secondary phase can substantially improve charge carrier separation and photocatalytic performance. In addition to engineering the electronic structure of composite photocatalysts, the preaccumulation of pollutants and their subsequent degradation is an effective strategy. This method decreases the distance between the adsorbed pollutant and the active sites for reactive oxygen species (ROSs) generation, enhancing the efficiency of the photocatalytic degradation process. In this study, we confined TiOx particles to the quantum dot size range by constructing a heterojunction with H-Beta zeolite, which contains defect-induced energy states within its wide band gap. This type of zeolite is particularly effective in adsorbing cationic azo dyes, facilitating pre-accumulation and degradation. The synthesized catalysts were extensively characterized using HRTEM to determine the average size of the TiOx particles and photoluminescence (PL) analysis to investigate charge carrier separation. Our results demonstrated that while TiOx alone showed negligible degradation efficiency, and no •OH were detected, the QD TiOx/Z4 composite achieved complete oxidation of CV by •OH, as confirmed by TOC analysis. The photocatalytic degradation mechanism was proposed based on these experimental findings. These insights could be of significant interest to researchers exploring defective semiconductors for photocatalytic oxidation of organic pollutants in the liquid phase under visible light (LED) irradiation.