Heterogeneous electron transfer at designed semiconductor/liquid interfaces. Rate of reduction of surface-confined ferricenium centers by solution reagents

Journal Article · Thu Aug 07 04:00:00 EDT 1980 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100453a008· OSTI ID:5130151

Lewis, N S; Bocarsly, A B; Wrighton, M S

Reduction of surface-confined ferricenium by solution reductants iodide, diindenyliron, (eta/sup 5/-C/sub 5/H/sub 5/)/sub 4/Fe/sub 4/(CO)/sub 4/, 1,1'-dimethylferrocene, ferrocene, and phenylferrocene has been studied in EtOH-0.1 M (n-Bu/sub 4/N)ClO/sub 4/ and also in H/sub 2/O-NaClO/sub 4/ for iodide. The surface-confined ferricenium can be generated on n-type Si by illumination of the electrode at some potential more positive than approx. -0.2 V vs. SCE. Linear sweep voltammetry was used to directly measure the time dependence of the surface ferricenium concentration in the dark and in the presence of the various reducing agents. The rate constant for the reaction with iodide was measured in both solvents, and the value in EtOH is somewhat lower than would be estimated from homogeneous solution reaction of ferricenium with iodide under the same conditions. Values of reaction rate constants for reaction with all other reductants indicate that the reduction rate is mass transport, not charge transfer, limited under the conditions employed. The relative ordering of the fast reductants has been determined to be diindenyliron > (eta/sup 5/-C/sub 5/H/sub 5/)/sub 4/Fe/sub 4/(CO)/sub 4/ approx. 1,1'-dimethylferrocene > ferrocene approx. phenylferrocene. Most of the derivatized surfaces have been prepared from (1,1'-ferrocenediyl)dichlorosilane, but preliminary results with polyvinylferrocene modified and (1,1'-ferrocenediyl)dimethylsilane derivatized surfaces are similar. Very high coverage surfaces from (1,1'-ferrocenediyl)dichlorosilane show some evidence for selective reduction of the more accessible ferricenium centers when a fast reductant is used. Steady-state photoanodic current at a given concentration of reductant generally accords well with the measured k/sub et/ values, and for the iodide experiments the steady-state photocurrent is directly proportional to surface coverage of electroactive ferrocene.

• Research Organization: Massachusetts Inst. of Tech., Cambridge
• OSTI ID: 5130151
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 84:16; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140501 -- Solar Energy Conversion-- Photovoltaic Conversion
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ALCOHOLS
ALKALI METAL COMPOUNDS
CHEMICAL REACTIONS
CHLORINE COMPOUNDS
COMPLEXES
CONVERSION
DATA
DIENES
DIRECT ENERGY CONVERTERS
ENERGY CONVERSION
ETHANOL
EXPERIMENTAL DATA
FERROCENE
HALIDES
HALOGEN COMPOUNDS
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INFORMATION
IODIDES
IODINE COMPOUNDS
IRON COMPLEXES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PERCHLORATES
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
POLYENES
REDUCTION
SODIUM COMPOUNDS
SODIUM PERCHLORATES
SOLAR ENERGY CONVERSION
TRANSITION ELEMENT COMPLEXES
WATER