### Abstract

The impedance of solid electrodes in the absence of faradaic reactions usually deviates from purely capacitive behaviour. The widely accepted explanations of this "capacitance dispersion" are based on the assumption that owing to surface roughness, or porosity, or spatially inhomogeneous capacitance density, the current density along the surface is not homogeneous, and thus capacitance dispersion is purely of geometric origin. We show that this view is not correct in the case of rough electrodes because capacitance dispersion due to irregular geometry appears at much higher frequencies than is usual in electrochemical methodologies. We present impedance spectra measured on platinum electrodes of various roughnesses in aqueous solutions to demonstrate that capacitance dispersion on rough electrodes is of interfacial origin and is due to adsorption effects. The old finding that the rougher the surface the larger the capacitance dispersion, can be rationalized alternatively in such a way that increasing roughness may broaden the time constant distribution of adsorption kinetics and may therefore increase the capacitance dispersion.

Original language | English |
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Pages (from-to) | 111-125 |

Number of pages | 15 |

Journal | Journal of Electroanalytical Chemistry |

Volume | 364 |

Issue number | 1-2 |

DOIs | |

Publication status | Published - Jan 31 1994 |

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### ASJC Scopus subject areas

- Chemical Engineering(all)
- Analytical Chemistry
- Electrochemistry

### Cite this

**Impedance of rough capacitive electrodes.** / Pajkossy, T.

Research output: Contribution to journal › Article

*Journal of Electroanalytical Chemistry*, vol. 364, no. 1-2, pp. 111-125. https://doi.org/10.1016/0022-0728(93)02949-I

}

TY - JOUR

T1 - Impedance of rough capacitive electrodes

AU - Pajkossy, T.

PY - 1994/1/31

Y1 - 1994/1/31

N2 - The impedance of solid electrodes in the absence of faradaic reactions usually deviates from purely capacitive behaviour. The widely accepted explanations of this "capacitance dispersion" are based on the assumption that owing to surface roughness, or porosity, or spatially inhomogeneous capacitance density, the current density along the surface is not homogeneous, and thus capacitance dispersion is purely of geometric origin. We show that this view is not correct in the case of rough electrodes because capacitance dispersion due to irregular geometry appears at much higher frequencies than is usual in electrochemical methodologies. We present impedance spectra measured on platinum electrodes of various roughnesses in aqueous solutions to demonstrate that capacitance dispersion on rough electrodes is of interfacial origin and is due to adsorption effects. The old finding that the rougher the surface the larger the capacitance dispersion, can be rationalized alternatively in such a way that increasing roughness may broaden the time constant distribution of adsorption kinetics and may therefore increase the capacitance dispersion.

AB - The impedance of solid electrodes in the absence of faradaic reactions usually deviates from purely capacitive behaviour. The widely accepted explanations of this "capacitance dispersion" are based on the assumption that owing to surface roughness, or porosity, or spatially inhomogeneous capacitance density, the current density along the surface is not homogeneous, and thus capacitance dispersion is purely of geometric origin. We show that this view is not correct in the case of rough electrodes because capacitance dispersion due to irregular geometry appears at much higher frequencies than is usual in electrochemical methodologies. We present impedance spectra measured on platinum electrodes of various roughnesses in aqueous solutions to demonstrate that capacitance dispersion on rough electrodes is of interfacial origin and is due to adsorption effects. The old finding that the rougher the surface the larger the capacitance dispersion, can be rationalized alternatively in such a way that increasing roughness may broaden the time constant distribution of adsorption kinetics and may therefore increase the capacitance dispersion.

UR - http://www.scopus.com/inward/record.url?scp=0001706901&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0001706901&partnerID=8YFLogxK

U2 - 10.1016/0022-0728(93)02949-I

DO - 10.1016/0022-0728(93)02949-I

M3 - Article

AN - SCOPUS:0001706901

VL - 364

SP - 111

EP - 125

JO - Journal of Electroanalytical Chemistry

JF - Journal of Electroanalytical Chemistry

SN - 0022-0728

IS - 1-2

ER -