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

Abstract

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)bipyridinium 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 ca..