Halogen poisoning effect of Pt-TiO2 for formaldehyde catalytic oxidation performance at room temperature

•The Pt-TiO2 catalyst is deactivated by adsorption of halogen ions.•The halogen poison is mainly attributed to the active site blocking of the Pt surface.•Halogen ions and Pt form PtX coordination bonds.•Large halogen diameter exhibits severe poisoning effect. Catalytic decomposition of formaldehyde...

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Bibliographic Details
Published in:Applied surface science 2016-02, Vol.364, p.808-814
Main Authors: Zhu, Xiaofeng, Cheng, Bei, Yu, Jiaguo, Ho, Wingkei
Format: Article
Language:English
Subjects:
Catalysis
Catalysts
Catalytic oxidation
Decomposition
Formaldehyde
Halogen poisoning
Halogens
Platinum
Poisons
Pt-TiO2
Surface chemistry
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Summary:•The Pt-TiO2 catalyst is deactivated by adsorption of halogen ions.•The halogen poison is mainly attributed to the active site blocking of the Pt surface.•Halogen ions and Pt form PtX coordination bonds.•Large halogen diameter exhibits severe poisoning effect. Catalytic decomposition of formaldehyde (HCHO) at room temperature is an important method for HCHO removal. Pt-based catalysts are the optimal catalyst for HCHO decomposition at room temperature. However, the stability of this catalyst remains unexplored. In this study, Pt-TiO2 (Pt-P25) catalysts with and without adsorbed halogen ions (including F−, Cl−, Br−, and I−) were prepared through impregnation and ion modification. Pt-TiO2 samples with adsorbed halogen ions exhibited reduced catalytic activity for formaldehyde decomposition at room temperature compared with the Pt-TiO2 sample; the catalytic activity followed the order of F-Pt-P25, Cl-Pt-P25, Br-Pt-P25, and I-Pt-P25. Characterization results (including XRD, TEM, HRTEM, BET, XPS, and metal dispersion) showed that the adsorbed halogen ions can poison Pt nanoparticles (NPs), thereby reducing the HCHO oxidation activity of Pt-TiO2. The poison mechanism is due to the strong adsorption of halogen ions on the surface of Pt NPs. The adsorbed ions form coordination bonds with surface Pt atoms by transferring surplus electrons into the unoccupied 5d orbit of the Pt atom, thereby inhibiting oxygen adsorption and activation of the Pt NP surface. Moreover, deactivation rate increases with increasing diameter of halogen ions. This study provides new insights into the fabrication of high-performance Pt-based catalysts for indoor air purification.
ISSN:0169-4332
1873-5584
DOI:10.1016/j.apsusc.2015.12.115