Corrosion-Related Degradation Phenomena in PEM Water Electrolysis - an Industrial Perspective
Authors: Weineck Nina , Kessler Florian , Ghicov Andrei , Dobrenizki Ladislaus 
Published: December 2024

One of the most reliable ways to produce green hydrogen is to use electrolysis systems from renewable energy sources. Proton exchange membrane water electrolysis (PEMWE) is one of the most promising electrolyzer technologies. To reach the goal of 1 Dollar per 1 kilogram of hydrogen in 1 decade – launched by the Department of Energy on June 7, 2021 [1] a long lifetime of electrolysis systems is key. The research focus is therefore to achieve low degradation rates for PEMWE-systems, measured in µV/h.

Within this presentation two different aspects of degradation related to metallic parts within the stack and within the process technology will be presented briefly. From this, open research questions concerning these aspects will be derived and their evaluation discussed. This industrial view reveals the needs and possible future development-trends of large-scale PEM water electrolyzer manufacturers.

First, corrosion of metallic parts, and thereby ion release into the process water, should be avoided as much as possible. It is well known that metal cations can lower the cell performance or even accelerate membrane degradation. The influence of stainless steel parts on PEMWE degradation has been studied by performing electrolysis tests on two different test-stands. One is made of commonly used stainless steel pipes and a stainless steel heat exchanger and the other is made of plastic piping and a titanium heat exchanger to exclude contamination from the Balance of Plant. In following electrolysis experiments on the plastic test-stand, titanium cell components have been subsequently replaced by stainless steel cell components. Resulting contamination (determined with ICP-MS) will be presented, and future work will be addressed as starting point for academic research.

Next, ohmic resistances in the PEMWE cells should be low to achieve low cell voltages. High anodic potentials within the electrolyzer cell can lead to growing oxide layers with poor electrical conductivity. The resulting additional ohmic resistance increases cell voltage over time and therefore promotes cell degradation. Especially for titanium, the commonly applied metal under anodic PEMWE conditions, it is known that growing Ti-oxide layers can result in increased cell voltages. Consequently, the impact of conductive coatings on different cell components on the degradation rate has been studied. Bipolar plates, coarse gas diffusion layers and porous transport layers have been coated with noble metals. The influence of these coatings on cell performance will be presented, and open questions will be addressed.

Finally, for the evaluation of the above-mentioned aspects, ex-situ experiments should be performed prior to electrolysis experiments. They are much easier to perform, reduce cost and time and allow a more separate look on certain material properties than in an electrolysis cell where the interaction of many parts needs to be considered. When compared to PEM fuel cells, no comparably clear guidance exists for the study of metallic parts for PEMWE [2]. We will provide insights on “how to perform ex-situ corrosion experiments” for PEMWE applications as a guidance for future testing based on the experience from researchers from both, academia and industry [3].

In conclusion, several sources for metal contamination exist in PEMWE-systems which can have a significant influence on degradation rates. Unfortunately, only limited research is available on the criticality of different contamination types. Furthermore, long-term stability information and degradation mechanisms on coating are of great importance as the currently used materials are rare. In addition, it is a challenge to generate a common understanding of suitable test conditions to simulate PEMWE-environment in ex-situ testing which would simplify improving components.

[1] Department of Energy, Hydrogen and Fuel Cell technologies Office

https://www.energy.gov/eere/fuelcells/hydrogen-shot [latest access: 15.03.2024]

[2] Department of Energy, Hydrogen and Fuel Cell technologies Office: DOE Technical Targets for Polymer Electrolyte Membrane Fuel Cell Components

https://www.energy.gov/eere/fuelcells/doe-technical-targets-polymer-electrolyte-membrane-fuel-cell-components [latest access: 15.03.2024]

[3] L. H. Prado et al., to be submitted

Figure 1