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Operando Laboratory X-Ray Imaging of Silver-Based Gas Diffusion Electrodes during Oxygen Reduction Reaction in Highly Alkaline Media

1
Institute of Applied Materials, Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
2
Institute of Chemistry and Biochemistry, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
3
Institute of Chemical and Electrochemical Process Engineering, Clausthal University of Technology, Leibnizstrasse 17, 38678 Clausthal-Zellerfeld, Germany
4
Department of Materials Science and Technology, Technical University Berlin, Hardenbergstr. 36, 14109 Berlin, Germany
*
Author to whom correspondence should be addressed.
Materials 2019, 12(17), 2686; https://doi.org/10.3390/ma12172686
Received: 8 June 2019 / Revised: 19 August 2019 / Accepted: 20 August 2019 / Published: 22 August 2019
Operando laboratory X-ray radiographies were carried out for imaging of two different silver-based gas diffusion electrodes containing an electroconductive Ni mesh structure, one gas diffusion electrode composed of 95 wt.% Ag and 5 wt.% polytetrafluoroethylene and one composed of 97 wt.% Ag and 3 wt.% polytetrafluoroethylene, under different operating parameters. Thereby, correlations of their electrochemical behavior and the transport of the 30 wt.% NaOH electrolyte through the gas diffusion electrodes were revealed. The work was divided into two parts. In the first step, the microstructure of the gas diffusion electrodes was analyzed ex situ by a combination of focused ion beam technology and synchrotron as well as laboratory X-ray tomography and radiography. In the second step, operando laboratory X-ray radiographies were performed during chronoamperometric measurements at different potentials. The combination of the ex situ microstructural analyses and the operando measurements reveals the impact of the microstructure on the electrolyte transport through the gas diffusion electrodes. Hence, an impact of the Ni mesh structure within the gas diffusion electrode on the droplet formation could be shown. Moreover, it could be observed that increasing overpotentials cause increasing electrolyte transport velocities and faster droplet formation due to electrowetting. In general, higher electrolyte transport velocities were found for the gas diffusion electrode with 97 wt.% Ag in contrast to that with 95 wt.% Ag. View Full-Text
Keywords: operando; X-ray imaging; gas diffusion electrode; oxygen-depolarized cathode; oxygen reduction reaction; chlor-alkali electrolysis operando; X-ray imaging; gas diffusion electrode; oxygen-depolarized cathode; oxygen reduction reaction; chlor-alkali electrolysis
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Paulisch, M.C.; Gebhard, M.; Franzen, D.; Hilger, A.; Osenberg, M.; Kardjilov, N.; Ellendorff, B.; Turek, T.; Roth, C.; Manke, I. Operando Laboratory X-Ray Imaging of Silver-Based Gas Diffusion Electrodes during Oxygen Reduction Reaction in Highly Alkaline Media. Materials 2019, 12, 2686.

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