Visible light photolysis of hydrogen iodide using sensitized layered metal oxide semiconductors: The role of surface chemical modification in controlling back electron transfer reactions

Geoffrey B. Saupe, Thomas E. Mallouk, Won Kim, Russell H. Schmehl

Research output: Contribution to journalArticle

90 Scopus citations

Abstract

The internally platinized wide bandgap semiconductor K4Nb6O17 can be sensitized by [(bpy)2Ru(4-(2,2′-bipyrid-4-yl)-phenylphosphonic acid](PF6)2 (1). In aqueous iodide solutions at pH 2, the visible light photolysis of HI, to form H2 and I3-, is catalyzed by 1/K4-xHxNb6O17/Pt. The strong bond between the surface and the phosphonate group of 1 allows one to adsorb other surface species, which decrease the rate of the back electron transfer reaction between conduction band electrons and I3- ions. Methylphosphonic acid and undecylphosphonic acid do not form good surface monolayers on 1/K4-xHxNb6O17 and do not increase the rate of hydrogen evolution. Anionic surface modifiers [TiNbO5]nn-, derived from exfoliation of KTiNbO5, and poly(styrenesulfonate), PSS, increase the initial hydrogen evolution rate by factors of 3 and 5, respectively. In the latter case, the initial quantum yield for HI photolysis is ca. 3%. Transient diffuse reflectance spectroscopy was used to monitor the formation and disappearance of I3- ions with 1/K4-xHxNb6O17 and PSS/ 1/K4-xHxNb6O17. The rate constant for the back electron transfer reaction between conduction band electrons and I3- ions decreases from 3.17 (±0.03) × 107 to 3.01(±0.02) × 106 M-1 s-1 upon adsorption of PSS.

Original languageEnglish (US)
Pages (from-to)2508-2513
Number of pages6
JournalJournal of Physical Chemistry B
Volume101
Issue number14
StatePublished - Apr 3 1997

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

Fingerprint Dive into the research topics of 'Visible light photolysis of hydrogen iodide using sensitized layered metal oxide semiconductors: The role of surface chemical modification in controlling back electron transfer reactions'. Together they form a unique fingerprint.

  • Cite this