Interfacial electron-transfer reactions in colloidal semiconductor dispersions. Kinetic analysis

Journal Article · Thu Jul 22 04:00:00 EDT 1982 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100212a031· OSTI ID:6462592

Graetzel, M; Frank, A J

A kinetic model is presented describing interfacial electron-transfer reactions in colloidal semiconductor dispersions induced by an ultrashort light pulse. The three elementary steps considered are (i) diffusion of charge carriers from the particle interior to the interphase, (ii) encounter-complex formation, and (iii) interfacial electron transfer. The first process is shown to occur so rapidly in colloidal particles that it does not contribute to the overall kinetics of the charge-transfer event. Steps ii and iii can be treated by solving the reaction-diffusion equation, thus obtaining an expression relating the observed bimolecular rate constant to the rate constant for heterogeneous electron transfer at the particle surface. The model is used to analyze the previously observed reduction of methylviologen (MV/sup 2 +/) by conduction-band electrons produced via laser excitation of TiO/sub 2/ colloids. The heterogeneous rate constant for electron transfer k/sub et/ follows a Tafel relation at pH greater than or equal to 5. Its value is k/sub et//sup 0/ = 4 x 10/sup -3/ cm/s at pH 5.4 where the conduction-band potential of the colloidal particle is equal to the standard potential of the MV/sup 2 +///sup +/ couple. The transfer coefficient obtained is 0.52. 3 figures.

• Research Organization: Solar Energy Research Inst., Golden, CO
• OSTI ID: 6462592
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 86:15; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
080106 -- Hydrogen-- Production-- Biosynthesis & Photochemical Processes
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400500 -- Photochemistry
AZINES
BIPYRIDINES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COLLOIDS
DECOMPOSITION
DIFFUSION
DISPERSIONS
ELECTROMAGNETIC RADIATION
ELECTRON TRANSFER
ENERGY-LEVEL TRANSITIONS
EQUATIONS
EXCITATION
HETEROCYCLIC COMPOUNDS
KINETICS
LASER RADIATION
MATERIALS
MATHEMATICAL MODELS
NUMERICAL SOLUTION
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PARTICLE SIZE
PH VALUE
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PYRIDINES
RADIATIONS
REACTION KINETICS
SEMICONDUCTOR MATERIALS
SIZE
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS