Degradation of oxygen-depolarized Ag-based gas diffusion electrodes for chlor-alkali cells |
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Authors: | S Siracusano T Denaro V Antonucci A S Aricò C Urgeghe F Federico |
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Affiliation: | (1) CNR-ITAE, Via Salita Santa Lucia Sopra Contesse 5, Messina, 98126, Italy;(2) Industrie De Nora S.p.A., via Bistolfi 35, Milan, 20134, Italy |
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Abstract: | Oxygen-depolarized cathodes consisting of gas-diffusion electrodes (GDEs) for electrolysis in a chlor-alkali cell at 90 °C
were studied. The electrode design was based on a carbon-free catalyst and comprised of a mixture of micronized silver particles,
a small amount of Hg and PTFE binder. The cathodes were investigated by electrochemical measurements, and surface and morphological
analyses before and after different operation times in chlor-alkali cells. Electrode stability was investigated by life-time
tests. The surface properties of gas diffusion electrodes were studied for both fresh and used cathodes by X-ray photoelectron
spectroscopy (XPS). Transmission (TEM) and scanning electron microscopy (SEM-EDX) were used to investigate morphology. The
bulk of gas diffusion electrodes was studied by X-ray diffraction (XRD) and thermogravimetric analysis (TG-DSC). At least
two main degradation processes that occur on different time-scales were identified and attributed to segregation and loss
of the second metal at the interface and a decrease in the hydrophilic properties with time. Furthermore, an increase in the
precipitation of compounds from the reaction process also decreased performance by the occlusion of reaction pores. |
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Keywords: | Oxygen reduction cathode Chlor-alkali electrolysis Gas diffusion electrode Carbon-free catalyst |
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