Electron Transfer Kinetics at Modified Carbon Electrode Surfaces: The Role of Specific Surface Sites

The electron transfer (El') kinetics of Ru(NH~)~~+/~+, II-C~~~-/~-, Fc?(CN)~~-/~-, Feaq2+/3+, and Vaq2+l3+ were examined on several modified glassy carbon surfaces. The kinetics of the aquated ions were very sensitive to the density of surface oxides, while those of the other redox systems were not. In particular, chemical derhalization of surface carbonyl groups decreased the rate of electron transfer with Fe3+l2+ by 2-3 orders of magnitude but had little effect on Ru(NH~)~~+/~+ or Ircl~~-/~-. The electron trader rates for Fe31/2+ correlated with surface C=O density determined by resonance Raman spectroscopy. Neutral, cationic, and anionic nonspecific adsorbers decreased the rates of ET with the aquated ions ap proximately equally but had little effect on Ru(NH3)62-/3f. The redox systems studied were classified into two groups: those which are catalyzed by surface carbonyl groups and those which are not. Possible catalytic mechanisms are considered. A significant effort by many laboratories has been directed toward understanding the relationship between surface structure and electron transfer reactivity for carbon Complex surface chemistry and an often unknown level of surface impurities have made it difticult to determine the important structural variables controlling carbon electrode reactivity. At least three major phenomena affect electron transfer (m? reactivity, and these vary in importance for different redox systems and solution conditions. First, many redox systems (e.g., Fe(CN),j3-14-, ascorbic acid, dopamine) are very sensitive to surface cleanliness, and observed ET rates are strongly dependent on surface hist~ry.~.'~ Second, the microstructure of the carbon has a large effect on most redox systems, with the basal plane of highly ordered pyrolytic graphite (HOPG) exhibiting much slower ET

[1]  R. McCreery,et al.  Electron Transfer Kinetics of Aquated Fe + 3 / + 2, Eu + 3 / + 2, and V + 3 / + 2 at Carbon Electrodes Inner Sphere Catalysis by Surface Oxides , 1993 .

[2]  T. Kuwana,et al.  Activation and deactivation of glassy carbon electrodes , 1985 .

[3]  T. Kuwana,et al.  Radiofrequency oxygen plasma treatment of pyrolytic graphite electrode surfaces , 1977 .

[4]  R. McCreery,et al.  Anthraquinonedisulfonate adsorption, electron-transfer kinetics, and capacitance on ordered graphite electrodes: the important role of surface defects , 1992 .

[5]  C. Barbero,et al.  Studies of surface-modified glassy carbon electrodes obtained by electrochemical treatment: Its effect on Ru(bpy)2+3 adsorption and the electron transfer rates of the Fe2+/Fe3+ couple , 1988 .

[6]  R. Wightman,et al.  The effect of pH on some outer-sphere electrode reactions at carbon electrodes , 1985 .

[7]  T. Gansler,et al.  Characterization of human breast biopsy specimens with near-IR Raman spectroscopy. , 1994, Analytical chemistry.

[8]  R. Engstrom,et al.  Characterization of electrochemically pretreated glassy carbon electrodes , 1984 .

[9]  T. Meyer,et al.  Electrocatalysis of proton-coupled electron-transfer reactions at glassy carbon electrodes , 1985 .

[10]  Z. Nagy,et al.  Kinetics of the Ferrous/Ferric Electrode Reaction in the Absence of Chloride Catalysis , 1987 .

[11]  R. McCreery,et al.  Resonance Raman Observation of Surface Carbonyl Groups on Carbon Electrodes Following Dinitrophenylhydrazine Derivatization , 1995 .

[12]  R. McCreery,et al.  Adsorption of catechols on fractured glassy carbon electrode surfaces , 1992 .

[13]  Werner G. Kuhr,et al.  Methods to improve electrochemical reversibility at carbon electrodes , 1984 .

[14]  Harry O. Finklea,et al.  Electron-transfer kinetics in organized thiol monolayers with attached pentaammine(pyridine)ruthenium redox centers , 1992 .

[15]  R. McCreery,et al.  Diagnosis of adsorption on solid electrodes with semiintegral voltammetry , 1988 .

[16]  T. Kuwana,et al.  Oxidative mechanism of ascorbic acid at glassy carbon electrodes , 1986 .

[17]  Theodore Kuwana,et al.  Electrocatalysis of dihydronicotinamide adenosine diphosphate with quinones and modified quinone electrodes , 1978 .

[18]  R. McCreery,et al.  Control of reactivity at carbon electrode surfaces , 1994 .

[19]  A. Bond,et al.  Electrochemistry of cytochrome c, plastocyanin, and ferredoxin at edge- and basal-plane graphite electrodes interpreted via a model based on electron transfer at electroactive sites of microscopic dimensions in size , 1989 .

[20]  L. Peter,et al.  The influence of alkali metal cations on the rate of the Fe(CN)64−/Fe(CN)63− electrode process , 1976 .

[21]  R. McCreery,et al.  Effects of Redox System Structure on Electron-Transfer Kinetics at Ordered Graphite and Glassy Carbon Electrodes , 1992 .

[22]  R. McCreery,et al.  Anomalously Slow Electron Transfer at Ordered Graphite Electrodes: Influence of Electronic Factors and Reactive Sites , 1994 .

[23]  R. McCreery,et al.  Quantitative correlations of heterogeneous electron-transfer kinetics with surface properties of glassy carbon electrodes , 1990 .

[24]  R. McCreery,et al.  Quantitative relationship between electron transfer rate and surface microstructure of laser-modified graphite electrodes , 1989 .

[25]  R. McCreery,et al.  Laser activation of carbon electrodes. Relationship between laser-induced surface effects and electron transfer activation , 1988 .

[26]  R. Crooks,et al.  Adsorption and electrode reactions of disulfonated anthraquinones at mercury electrodes , 1990 .

[27]  R. D. Cannon.  Electron Transfer Reactions , 1980 .