@inproceedings{62814,
  abstract     = {{Porous carbons are prominent electrode materials in energy storage applications such as supercapacitors. However, rational materials development is hampered by difficulties in interpreting electrochemical impedance spectra (EIS) and drawing conclusions about promising aspects of device improvement. Here, we characterized electrodes consisting of activated carbon with polyacrylic acid binder in four different concentrations of sulfuric acid, using cyclic voltammetry and electrochemical impedance spectroscopy. Both datasets were evaluated with simple equivalent circuits and comparatively analyzed. Conductivity of the electrolyte was independently measured. Cyclic voltammograms (CV) show larger resistance and capacitance at low scan rates. Resistances obtained from EIS are in good agreement with those obtained by cyclic voltammograms particularly at high scan rates. The comparison against specific electrolyte resistance can reveal whether resistances within the solid electrode architecture or resistances within the electrolyte, partially confined by pores, are the dominant cause of increased resistance at low scan rate. Comparison between CV and EIS points to the main electrode capacitance being described by a constant phase element (CPE) used to fit the low-frequency region of EIS.}},
  author       = {{Reinke, Sebastian and Khamitsevich, Vera and Linnemann, Julia}},
  booktitle    = {{2024 International Workshop on Impedance Spectroscopy (IWIS)}},
  keywords     = {{electrochemical impedance spectroscopy, distorted cyclic voltammograms, supercapacitors, carbon}},
  publisher    = {{IEEE}},
  title        = {{{Complementary Analysis of Cyclic Voltammograms and Impedance Spectra of Porous Carbon Electrodes}}},
  doi          = {{10.1109/iwis63047.2024.10847115}},
  year         = {{2025}},
}

@inproceedings{62812,
  abstract     = {{Attributing features of electrochemical impedance spectra to electrochemical phenomena is both crucial and frequently ambiguous. To elucidate the origin of the ohmic part of the spectrum, activated carbon electrodes were prepared with different contents of polyacrylic acid as binder. Their impedance spectra and cyclic voltammograms were recorded using sulfuric acid of five different concentrations as the electrolyte. To distinguish electrolyte resistance and resistances related to the activated carbon layer of the electrode, the specific electrolyte conductivity was independently measured and compared against the ohmic part of the electrochemical impedance spectra (EIS). The capacitive cyclic voltammograms show larger resistive contributions with higher scan rate and lower electrolyte conductivity. Comparing the ohmic part of the EIS to the specific resistance of the electrolyte, a linear function with no statistically significant offset was found. The ohmic part of the EIS, thus, reflects the electrolyte resistance, not that of the carbon electrode.}},
  author       = {{Reinke, Sebastian and Khamitsevich, Vera and Röth, Oliver and Linnemann, Julia}},
  booktitle    = {{2023 International Workshop on Impedance Spectroscopy (IWIS)}},
  keywords     = {{electrochemical impedance spectroscopy, supercapacitors, carbon}},
  publisher    = {{IEEE}},
  title        = {{{Assessment of the Physicochemical Meaning of the Ohmic Series Resistance Observed for High Frequencies in Electrochemical Impedance Spectra}}},
  doi          = {{10.1109/iwis61214.2023.10302764}},
  year         = {{2023}},
}

@article{62801,
  abstract     = {{The three-dimensional (3D) distribution of individual atoms on the surface of catalyst nanoparticles plays a vital role in their activity and stability. Optimising the performance of electrocatalysts requires atomic-scale information, but it is difficult to obtain. Here, we use atom probe tomography to elucidate the 3D structure of 10 nm sized Co2FeO4 and CoFe2O4 nanoparticles during oxygen evolution reaction (OER). We reveal nanoscale spinodal decomposition in pristine Co2FeO4. The interfaces of Co-rich and Fe-rich nanodomains of Co2FeO4 become trapping sites for hydroxyl groups, contributing to a higher OER activity compared to that of CoFe2O4. However, the activity of Co2FeO4 drops considerably due to concurrent irreversible transformation towards CoIVO2 and pronounced Fe dissolution. In contrast, there is negligible elemental redistribution for CoFe2O4 after OER, except for surface structural transformation towards (FeIII, CoIII)2O3. Overall, our study provides a unique 3D compositional distribution of mixed Co-Fe spinel oxides, which gives atomic-scale insights into active sites and the deactivation of electrocatalysts during OER.}},
  author       = {{Xiang, Weikai and Yang, Nating and Li, Xiaopeng and Linnemann, Julia and Hagemann, Ulrich and Ruediger, Olaf and Heidelmann, Markus and Falk, Tobias and Aramini, Matteo and DeBeer, Serena and Muhler, Martin and Tschulik, Kristina and Li, Tong}},
  issn         = {{2041-1723}},
  journal      = {{Nature Communications}},
  keywords     = {{electrocatalysis, oxygen evolution reaction, cobalt spinel, electrochemical impedance spectroscopy}},
  number       = {{1}},
  publisher    = {{Springer Science and Business Media LLC}},
  title        = {{{3D atomic-scale imaging of mixed Co-Fe spinel oxide nanoparticles during oxygen evolution reaction}}},
  doi          = {{10.1038/s41467-021-27788-2}},
  volume       = {{13}},
  year         = {{2022}},
}