PtOx-SnOx-TiO2 catalyst system for methanol photocatalytic reforming: Influence of cocatalysts on the hydrogen production
| Autor: | Judith Mihály, Péter Németh, András Tompos, Zoltán Pászti, Emília Tálas, László Korecz, Gábor P. Szijjártó, Attila Domján |
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| Rok vydání: | 2018 |
| Předmět: |
Anatase
Materials science Inorganic chemistry chemistry.chemical_element Nanoparticle 02 engineering and technology General Chemistry 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Catalysis 0104 chemical sciences law.invention chemistry.chemical_compound Chemical engineering chemistry law Photocatalysis Calcination Methanol 0210 nano-technology Tin Hydrogen production |
| Zdroj: | Catalysis Today. 306:71-80 |
| ISSN: | 0920-5861 |
| Popis: | Effects of modification of PtO x -TiO 2 photocatalysts by tin were elucidated by exploring relationships between the structural properties of variously prepared tin-loaded catalysts and their catalytic activity in methanol photocatalytic reforming. Tin free and amorphous tin-oxide decorated TiO 2 samples were prepared by sol-gel method from titanium-isopropoxide. In other approach, Sn was loaded onto the sol-gel prepared TiO 2 by impregnation followed by calcination. Pt was introduced by impregnation followed by either reduction in H 2 at 400 °C or calcination at 300 °C. TEM, XRD and Raman spectroscopic measurements proved that TiO 2 existed in the form of aggregates of polycrystalline anatase with primary particle size of 15–20 nm in all samples. Photocatalytic hydrogen production was influenced by the combined effect of many parameters. Both the presence of Sn and the way of Pt co-catalyst formation played important role in the activity of these photocatalysts. The Sn introduction by both sol-gel method and impregnation clearly enhanced the photocatalytic activity. 1 H MAS NMR measurements revealed that the Sn introduction reduced the amount of the terminal Ti-OH groups of relatively basic character considered to be unfavorable for the photocatalytic reaction. Presence of SnO x decreased the signal of the undesirable vacancies observed by ESR. Furthermore surface SnO x enhanced the dispersion of Pt. Formation of the Pt co-catalyst by calcination was more favorable than by H 2 treatment. In case of the calcined samples in situ reduction of the Pt nanoparticles at the beginning of the photocatalytic reaction was found to be favorable for the hydrogen production. The relatively modest photocatalytical activity obtained after high temperature H 2 treatment could be related to at least two processes in this system: (i) creation of unfavorable oxygen vacancies and (ii) segregation of SnO x to the surface of the Pt cocatalyst as the result of the air exposure of the alloy type Pt-Sn nanoparticles formed during the H 2 treatment, resulting in a decreased number of active sites for reduction of H + . |
| Databáze: | OpenAIRE |
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