TY - JOUR
T1 - Visible light photolysis of hydrogen iodide using sensitized layered metal oxide semiconductors
T2 - The role of surface chemical modification in controlling back electron transfer reactions
AU - Saupe, Geoffrey B.
AU - Mallouk, Thomas E.
AU - Kim, Won
AU - Schmehl, Russell H.
PY - 1997/4/3
Y1 - 1997/4/3
N2 - 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.
AB - 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.
UR - https://www.scopus.com/pages/publications/4043174761
UR - https://www.scopus.com/pages/publications/4043174761#tab=citedBy
U2 - 10.1021/jp9625319
DO - 10.1021/jp9625319
M3 - Article
AN - SCOPUS:4043174761
SN - 1520-6106
VL - 101
SP - 2508
EP - 2513
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 14
ER -