Electroless Preparation and ASAXS Microstructural Analysis of Pseudocapacitive Carbon Manganese Oxide Supercapacitor Electrodes

Weber, Christian; Reichenauer, Gudrun; Pflaum, Jens

doi:10.1021/la5027762

Journal Article

PUBDB-2015-06046

Electroless Preparation and ASAXS Microstructural Analysis of Pseudocapacitive Carbon Manganese Oxide Supercapacitor Electrodes

Weber, C.>Extern* ; Reichenauer, G. (Corresponding author)>Extern* ; Pflaum, J.

2015
ACS Publ. Washington, DC

Langmuir 31(2), 782 - 788 (2015) [10.1021/la5027762]

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Please use a persistent id in citations: doi:10.1021/la5027762

Abstract: Anomalous small angle X-ray scattering (ASAXS) has been utilized as a noninvasive, integral tool to access the structural properties of carbon xerogel–manganese oxide electrodes with nanometer resolution. As these electrodes constitute the elementary functional units in supercapacitors and as their microstructure governs the macroscopic electrical performance, it is essential to gain a detailed morphological understanding of the underlying carbon particle scaffold coated with manganese oxide. We demonstrate that, in this regard, ASAXS provides a powerful technique and in combination with a theoretical core–shell model enables a quantitative estimation of the relevant structural parameters. As a result, we determined the thicknesses of the solution deposited MnO$_{2}$ shells to range between 3 and 26 nm depending on the carbon particle size and thus on their effective surface area. By our core–shell modeling we conclude the revealed manganese oxide coatings on the carbon support to be rather thick, but nevertheless to show a high uniformity in thickness. At 1.8 ± 0.2 to 2.2 ± 0.1 g/cm$^{3}$ the related effective MnO$_{2}$ densities of the shells are about 30% lower than the corresponding bulk density of 3.0 g/cm$^{3}$. This mainly originates from a substructure within the shell, whose growth is controlled by a pronounced reduction of the manganese precursor during layer formation. Finally, the presented ASAXS data are complemented by SEM and N$_{2}$ sorption measurements, proving not only qualitatively the proposed flake-like MnO$_{2}$ surface morphology but also confirming quantitatively the manganese shell thickness, complementary, on a local scale.

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