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Evaluation of levels of defect sites present in highly ordered pyrolytic graphite electrodes using capacitive and faradaic current components derived simultaneously from large-amplitude fourier transformed ac voltammetric experiments

Journal Article


Abstract


  • The level of edge plane defect sites present in highly ordered pyrolytic graphite (HOPG) electrodes has been evaluated via analysis of dc, ac fundamental, and higherorder ac harmonics available from a single large-amplitude Fourier transformed (FT) ac voltammetric experiment. Deliberate introduction of a low level of edge plane defect was achieved by polishing, with a higher level being introduced via electrochemical pretreatment. Kinetics regimes associated with fast electron transfer on the edge plane defect sites and slow electron transfer on the basal plane surface are resolved under ac conditions when using the surface-sensitive [Fe(CN)6]3-/4- redox probe. However, because of their insensitivity to slow electron transfer, higher-order ac faradaic harmonics almost exclusively detect only the much faster processes that emanate from edge plane defect sites. Thus, detection of fourth- and higher-order ac Faradaic harmonic components that are devoid of background capacitive current is possible at freshly cleaved HOPG in the region near the reversible potential for the [Fe(CN)6]3-/4- process. Under these circumstances, dc cyclic voltammograms exhibit only reduction and oxidation peaks separated by more than 1 V. The fundamental ac harmonic provides detailed information on the capacitive current, which increases with the level of edge plane defect sites. Apparent charge transfer rate constants also can be derived from peak-to-peak separations obtained from the dc aperiodic component. Estimates of the percentage of edge plane defect sites based on ac higher harmonics, capacitance, and dc aperiodic component that are available from a single experiment have been compared. The edge plane defect levels deduced from capacitance (fundamental harmonic ac component) and higher harmonic Fara-daic currents are considered to be more reliable than estimations based on apparent rate constants derived from the dc aperiodic component or conventional dc cyclic voltammogram. © 2009 American Chemical Society.

Publication Date


  • 2009

Citation


  • Lee, C. Y., & Bond, A. M. (2009). Evaluation of levels of defect sites present in highly ordered pyrolytic graphite electrodes using capacitive and faradaic current components derived simultaneously from large-amplitude fourier transformed ac voltammetric experiments. Analytical Chemistry, 81(2), 584-594. doi:10.1021/ac801732g

Scopus Eid


  • 2-s2.0-60549102280

Start Page


  • 584

End Page


  • 594

Volume


  • 81

Issue


  • 2

Abstract


  • The level of edge plane defect sites present in highly ordered pyrolytic graphite (HOPG) electrodes has been evaluated via analysis of dc, ac fundamental, and higherorder ac harmonics available from a single large-amplitude Fourier transformed (FT) ac voltammetric experiment. Deliberate introduction of a low level of edge plane defect was achieved by polishing, with a higher level being introduced via electrochemical pretreatment. Kinetics regimes associated with fast electron transfer on the edge plane defect sites and slow electron transfer on the basal plane surface are resolved under ac conditions when using the surface-sensitive [Fe(CN)6]3-/4- redox probe. However, because of their insensitivity to slow electron transfer, higher-order ac faradaic harmonics almost exclusively detect only the much faster processes that emanate from edge plane defect sites. Thus, detection of fourth- and higher-order ac Faradaic harmonic components that are devoid of background capacitive current is possible at freshly cleaved HOPG in the region near the reversible potential for the [Fe(CN)6]3-/4- process. Under these circumstances, dc cyclic voltammograms exhibit only reduction and oxidation peaks separated by more than 1 V. The fundamental ac harmonic provides detailed information on the capacitive current, which increases with the level of edge plane defect sites. Apparent charge transfer rate constants also can be derived from peak-to-peak separations obtained from the dc aperiodic component. Estimates of the percentage of edge plane defect sites based on ac higher harmonics, capacitance, and dc aperiodic component that are available from a single experiment have been compared. The edge plane defect levels deduced from capacitance (fundamental harmonic ac component) and higher harmonic Fara-daic currents are considered to be more reliable than estimations based on apparent rate constants derived from the dc aperiodic component or conventional dc cyclic voltammogram. © 2009 American Chemical Society.

Publication Date


  • 2009

Citation


  • Lee, C. Y., & Bond, A. M. (2009). Evaluation of levels of defect sites present in highly ordered pyrolytic graphite electrodes using capacitive and faradaic current components derived simultaneously from large-amplitude fourier transformed ac voltammetric experiments. Analytical Chemistry, 81(2), 584-594. doi:10.1021/ac801732g

Scopus Eid


  • 2-s2.0-60549102280

Start Page


  • 584

End Page


  • 594

Volume


  • 81

Issue


  • 2