期刊
ACS CATALYSIS
卷 2, 期 8, 页码 1817-1828出版社
AMER CHEMICAL SOC
DOI: 10.1021/cs300273q
关键词
CO2 photoreduction; oxygen vacancy; TiO2; Brookite; In situ DRIFTS
资金
- National Science Foundation Division of Chemical, Bioengineering, Environmental, and Transport Systems [CBET-1067233, CBET-1067340]
- Directorate For Engineering
- Div Of Chem, Bioeng, Env, & Transp Sys [1067233] Funding Source: National Science Foundation
- Div Of Chem, Bioeng, Env, & Transp Sys
- Directorate For Engineering [1538402, 1067340] Funding Source: National Science Foundation
CO2 photoreduction with water vapor has been studied on three TiO2 nanocrystal polymorphs (anatase, rutile, and brookite) that were engineered with defect-free and oxygen-deficient surfaces, respectively. It was demonstrated that helium pretreatment of the as-prepared TiO2 at a moderate temperature resulted in the creation of surface oxygen vacancies (V-O) and Ti3+ sites on anatase and brookite but not on rutile. The production of CO and CH4 from CO2 photoreduction was remarkably enhanced on defective anatase and brookite TiO2 (up to 10-fold enhancement) as compared to the defect-free surfaces. Defective brookite was photocatalytically more active than anatase and rutile, probably because of a lower formation energy of Vo on brookite. The results from in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses suggested that (1) defect-free TiO2 was not active for CO2 photoreduction since no CO2- is generated, and (2) CO2 photoreduction to CO possibly underwent different reaction pathways on oxygen-deficient anatase and brookite via different intermediates (e.g., CO2- on anatase; CO2- and HCOOH on brookite). The combined DRIFTS and photoactivity studies reported in this paper have provided new insights to the role of surface defects in CO2 photoreduction TiO2 nanocrystals, and revealed significant information on the much less studied but promising brookite phase.
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