Photocatalytic CO 2 reduction with H 2O on TiO 2 nanocrystals: Comparison of anatase, rutile, and brookite polymorphs and exploration of surface chemistry

Lianjun Liu, Huilei Zhao, Jean M. Andino, Ying Li

Research output: Contribution to journalArticle

430 Citations (Scopus)

Abstract

CO 2 photoreduction with water vapor has been studied on three TiO 2 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 TiO 2 at a moderate temperature resulted in the creation of surface oxygen vacancies (V O) and Ti 3+ sites on anatase and brookite but not on rutile. The production of CO and CH 4 from CO 2 photoreduction was remarkably enhanced on defective anatase and brookite TiO 2 (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 V O on brookite. The results from in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses suggested that (1) defect-free TiO 2 was not active for CO 2 photoreduction since no CO 2 - is generated, and (2) CO 2 photoreduction to CO possibly underwent different reaction pathways on oxygen-deficient anatase and brookite via different intermediates (e.g., CO 2 - on anatase; CO 2 - 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 CO 2 photoreduction on TiO 2 nanocrystals, and revealed significant information on the much less studied but promising brookite phase.

Original languageEnglish
Pages (from-to)1817-1828
Number of pages12
JournalACS Catalysis
Volume2
Issue number8
DOIs
Publication statusPublished - Aug 3 2012

Keywords

  • Brookite
  • CO photoreduction
  • In situ DRIFTS
  • TiO
  • oxygen vacancy

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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