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Modeling the Electrochemical Impedance Spectra of Electroactive Pseudocapacitor Materials
- Source :
- Journal of The Electrochemical Society. 158:A678-A688
- Publication Year :
- 2011
- Publisher :
- The Electrochemical Society, 2011.
-
Abstract
- Measured electrochemical impedance spectra of porous electrodes comprised of redox-active ruthenium oxide and inert niobium hydroxide are compared with the results of structurally consistent mathematical models describing coupled processes of electron transport in the solid matrix, ion transport in the electrolyte, proton transport within the ruthenium oxide particles, and redox reaction on particle surfaces. Addition of moderate amounts of niobium to crystalline ruthenium oxide is found to improve the frequency response due to enhanced intraparticle proton transport. However, excessive niobium reduces ion and electron transport through the electrode thickness, reducing the available capacitance. Thus, an optimum composition is needed to achieve the best balance in transport properties. Near this optimum, the intraparticle proton transport undergoes a transition from a constant phase element (CPE) response for Ru-rich materials to a classical Warburg diffusion response for Nb-rich compositions. The CPE regime is analyzed in detail to identify fractal-like structures as well as alternative radial distributions of intraparticle proton diffusivity consistent with measured response. The models involving variations in radial diffusivity appear most probable and have nearly exponential decreases in radial diffusivity with distance from particle surfaces similar to a Debye distribution of charge carriers in an electric double layer.
- Subjects :
- Renewable Energy, Sustainability and the Environment
Chemistry
Constant phase element
Analytical chemistry
Niobium
chemistry.chemical_element
Electrolyte
Condensed Matter Physics
Thermal diffusivity
Electron transport chain
Ruthenium oxide
Surfaces, Coatings and Films
Electronic, Optical and Magnetic Materials
Proton transport
Pseudocapacitor
Materials Chemistry
Electrochemistry
Subjects
Details
- ISSN :
- 19457111 and 00134651
- Volume :
- 158
- Database :
- OpenAIRE
- Journal :
- Journal of The Electrochemical Society
- Accession number :
- edsair.doi...........df56710444a361816114866c9464147d