Differential Capacitance Study on the Basal Plane of Stress-Annealed Pyrolytic Graphite
CASE WESTERN RESERVE UNIV CLEVELAND OH DEPT OF CHEMISTRY
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The non-faradaic differential electrode capacity of the basal plane of high-pressure stress-annealed pyrolytic graphite has been examined in aqueous solution using an a.c. impedance bridge. The capacity has a near parabolic dependence on electrode potential with a minimum of approximately 3 microfarads sq cm in concentrated electrolytes and is pH independent. Studies in NaF solutions at concentrations in the range 0.9 to 0.00001M indicate that in the range of potential studied 0.5 to -0.5 V vs NHE the minimum capacity is best attributed to the space charge region within the graphite and not to the diffuse ionic layer. Apparently the potential of zero charge of the electrolyte is outside the potential range of the measurements.
- Physical Chemistry