Enhancing photocatalytic CO2 reduction by coating an ultrathin Al2O3 layer on oxygen deficient TiO2 nanorods through atomic layer deposition
| Autor: | Huilei Zhao, Wei Deng, Ying Li, Guiying Rao, Jiatang Chen |
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| Rok vydání: | 2017 |
| Předmět: |
Anatase
Materials science Passivation General Physics and Astronomy Nanotechnology 02 engineering and technology Surfaces and Interfaces General Chemistry engineering.material 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences 0104 chemical sciences Surfaces Coatings and Films Amorphous solid Atomic layer deposition Coating Chemical engineering engineering Photocatalysis Nanorod 0210 nano-technology Surface states |
| Zdroj: | Applied Surface Science. 404:49-56 |
| ISSN: | 0169-4332 |
| Popis: | In this work, anatase nanorods (ANR) of TiO2 with active facet {100} as the major facet were successfully synthesized, and reducing the ANR by NaBH4 led to the formation of gray colored oxygen deficient TiO2-x (ReANR). On the surface of ReANR, a thin layer of Al2O3 was deposited using atomic layer deposition (ALD), and the thickness of Al2O3 varied by the number of ALD cycles (1, 2, 5, 10, 50, 100, or 200). The growth rate of Al2O3 was determined to be 0.25 A per cycle based on high-resolution TEM analysis, and the XRD result showed the amorphous structure of Al2O3. All the synthesized photocatalysts (ANR, ReANR, and Al2O3 coated ReANR) were tested for CO2 photocatalytic reduction in the presence of water vapor, with CO detected as the major reduction product and CH4 as the minor product. Compared with ANR, ReANR had more than 50% higher CO production and more than ten times higher CH4 production due to the oxygen vacancies that possibly enhanced CO2 adsorption and activation. By applying less than 5 cycles of ALD, the Al2O3 coated ReANR had enhanced overall production of CO and CH4 than uncoated ReANR, with 2 cycles being the optimum, about 40% higher overall production than ReANR. Whereas, both CO and CH4 production decreased with increasing number of ALD cycles when more than 5 cycles were applied. Photoluminescence (PL) analysis showed an ultrathin layer of Al2O3 (2 cycles of ALD) coating on the ReANR was able to reduce the charge carrier recombination rate, likely because of the passivation of surface states. On the other hand, a relatively thick layer of Al2O3 may act as an insulation layer to prohibit electron migration to the catalyst surface. This work gives valuable insights on the application of ALD coating on photocatalysts to promote CO2 photoreduction to fuels. |
| Databáze: | OpenAIRE |
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