On-Line Monitoring of the Stability of Electrodes in Non-Aqueous Media

• Published in: Meeting abstracts (Electrochemical Society) Vol. MA2019-02; no. 44; p. 2050
• Main Authors: Ranninger, Johanna, Wachs, Susanne J., Möller, Jonas, Mayrhofer, Karl J. J., Berkes, Balázs B.
• Format: Journal Article
• Language: English
• Published: 01.09.2019
• ISSN: 2151-2043; 2151-2035
• DOI: 10.1149/MA2019-02/44/2050

Stability of electrochemical systems is particularly important in applications. No matter if it is a fuel cell, a battery, a supercapacitor, a construction subject to corrosion or an electrode used for synthesis, economic considerations require a certain lifetime of these systems. Depending on the systems, instability can have several causes, like changes in the mechanical or crystal structure of electrodes, oxidation of materials, decomposition of electrolytes, loss of percolation and electrical conductivity, or material loss due dissolution. Many of these processes happen slowly, causing only minimal performance loss within laboratory timescales. Their studies involve therefore usually long-term measurements with ex situ analysis. In situ, real-time analysis requires very sophisticated and usually coupled analysis methods. In this work we show a powerful approach to study dissolution phenomena in non-aqueous electrochemical systems. A scanning electrochemical flow cell (SFC) combined with on-line inductively coupled plasma mass spectrometric (ICP-MS) analysis has proven to be a very valuable tool for the study of stability of electrocatalysts in aqueous solutions. This coupled technique is mainly connected to the works of Dr. Mayrhofer and Dr. Cherevko. It was very appealing to develop this method further and make it useable in organic systems too. This task might seem for the first glance to be almost trivial, however, the harsh conditions caused by the organic electrolytes limit the usability of materials to contrive these systems to a huge extent. Furthermore, the ICP-MS is standardized mainly for aqueous media and a lot of experimental work has to be devoted for the optimization of the device for each individual organic solvent. Most of the chemicals used are sensitive to atmospheric components, like O 2 , H 2 O, CO 2 or even N 2 . Therefore, the experiments have to be carried out in a glovebox that ensures a controlled and very clean atmosphere. Platinum is often considered to be a model electrode and catalyst material. This metal is probably the most thoroughly studied one in electrochemistry, however, it still shows many interesting yet not well understood features. This is also true for the stability of the metal during potential cycling. The electrochemical stability window of organic electrolytes is usually much higher than that of water enabling the simultaneous cycling and downstream analysis of dissolution in a higher potential range. As a result, even the electrochemistry of platinum shows hitherto unveiled phenomena regarding its dissolution mechanism. In this work, we focus on the effect of water contamination, anions, cations and organic solvent molecules on the anodic and cathodic dissolution behavior of platinum. To demonstrate the benefits of this novel method on the field of non-aqueous electrochemistry the stability of other non-aqueous systems will be discussed shortly, too.