Dynamics of interfacial charge transfer in iron(III) oxide colloids

Journal Article · Thu Nov 17 04:00:00 EST 1988 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100334a049· OSTI ID:5994565

Mulvaney, P; Swayambunathan, V; Grieser, F; Meisel, D

The kinetics of electron and proton transfer to colloidal Fe(III) oxides have been examined as a function of pH, colloid size, crystal structure, and reductant concentration. Electron injection into the colloidal particles was achieved using pulse-radiolytically generated methylviologen and 1,1'-bis(3-sulfonatopropyl)bipyridium radicals. The rate of electron transfer is governed both by the free energy difference between the redox potential of the redox couple in the electrolyte and the Fermi level in the solid and by the electrostatic interaction between the reducing radical and the electric double layer at the interface. The contribution of the latter to the rate constant dominates in cases of highly charged reductants and in particular for positively charged donors. For small particles, proton consumption occurs concomitantly with electron transfer, whereas the proton uptake lags behind the electron transfer to the larger particles in the suspensions. However, the polarization lasts no more than a few milliseconds. In accord with previous results, evidence is also presented which shows that the injected electrons can be trapped either at the surface or in the interior of the particle. The lower the pH and the smaller the particle radius, the greater is the friction of electrons trapped in the surface. A fast pH buffering by surface hydroxy groups when the colloid is near the point of zero charge (pzc) was also observed.

• Research Organization: Univ. of Melbourne, Parkville (Australia)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5994565
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 92:23; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CHALCOGENIDES
CHEMICAL REACTION KINETICS
COHERENT SCATTERING
COLLOIDS
CRYSTAL STRUCTURE
DATA
DIFFRACTION
DISPERSIONS
DYNAMICS
ELECTRON TRANSFER
EXPERIMENTAL DATA
HYDROGEN TRANSFER
INFORMATION
IRON COMPOUNDS
IRON OXIDES
KINETICS
MECHANICS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PARTICLE SIZE
PH VALUE
QUANTITY RATIO
REACTION KINETICS
SCATTERING
SIZE
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION