Degradation of Sb-Doped SnO2 Supported IrRu-Based Electrocatalysts for PEM Water Electrolysis Via Accelerated Stress Protocols

Abstract

Proton exchange membrane (PEM) water electrolyzers offer a very promising option to offset the environmental burden of conventional hydrogen production by splitting water into high purity hydrogen and oxygen without releasing carbon dioxide as by-product. However, the corrosive nature of the process makes it dependent on expensive materials, such as iridium (Ir), ruthenium (Ru) or titanium (Ti), which makes the upscaling of the technology considerably more difficult [1, 2]. To ensure industrial success of this technology, the study of the mechanisms involved in the degradation of the cell components is of great importance. Particularly, the development of accelerated stress test protocols has attracted attention in recent years, due to their potential to yield representative data pertaining degradation without incurring long testing times that would meet the typical industrial standards of 20,000 to up to 50,000 hours [3].Several strategies to investigate the various degradation mechanisms have been discussed in recent years in the literature. Particularly, Spöri pointed out the difference between transient and static operation and the degradation mechanisms triggered by each of these modes, while also investigating the intrinsic mechanisms of the catalyst via rotating disk electrode analysis [3]. Meanwhile, Frensch explored in their work the relation of cathodic fluoride release with different current density profiles and different temperatures [4]. Furthermore, attempts have been made to increase the electrochemical stability of oxygen evolution reaction (OER) electrocatalysts by adding a support material to the catalyst layer. This was described by Saveleva in their work, as they found evidence that supporting Ir on antimony-doped tin oxide (Sb-doped SnO2) resulted in a preferential dissolution of Sb and Sn, thus noticeably reducing the dissolution rate of Ir [2].In this work, the electrochemical activity and stability of newly developed IrRu OER catalysts supported on Sb-doped SnO2 is studied in a single cell setup. The catalyst and support materials were synthetized as part of the study. For the preparation of the MEAs the fabricated materials were used with membranes and ionomers which are commercially available. The prepared MEAs were analyzed using both static and dynamic current profiles with a current range of up to 4 A cm-2. To understand the different mechanisms and material dependencies at play during characterization, the MEA configuration (membrane type, material ratios, ionomer) was varied. The first screenings with different MEA configurations not only suggest a strong stability with the catalyst loading, as it was previously observed by Alia [5], but also a strong dependence on the anodic ionomer content, which reflects in the degradation rate in the first hundred hours of test.