D1.3: Degradation Mechanisms in Automotive Fuel Cell Systems

Degradation mechanisms in automotive PEM fuel cell systems are categorized, in this deliverable, in regard to the degradation mechanisms of each component of PEM fuel cell stack, namely: membrane, catalyst layers, gas diffusion layers, bipolar plates and sealing gaskets. The underlying degradation mechanisms of each of the aforementioned structural component of the cell are decomposed with brief explanation of the physical phenomena causing the degradation and the inter-relation of the influence of one constituent of the structural component on the other. The analysis based on available data from the project partners and literature survey leads to the conclusion that the main degradation mechanisms of the cell depend on high number of different variables, such as MEA manufacturing process, assembly, operating conditions, thermal cycling, relative humidity cycling, subfreezing ambient temperature, load cycling, etc. Therefore, the main degradation mechanisms have to be determined based on the particular and highly detailed cell configuration. The mitigation strategies are proposed for each structural component, although some of the requirements may be in confrontation with each other. PEM fuel cell degradation cannot be completely suppressed, however by closely monitoring the cell operation and adapting the operating conditions to the particular cell design, they can be significantly minimized. The accelerated stress tests are surveyed and listed for each structural component, and some of them are compared vs. real-time investigation under certain operating conditions (e.g. carbon corrosion) with good agreement. General conclusion is that the ability of Degradation Mechanisms in Automotive Fuel Cell Systems Page 2 of 46 the accelerated stress tests to predict the real-time operating conditions inside the cell is of a limited reliability, due to the nature of simulating only a limited number of degradation mechanisms at the same time, with quite limited influence on other structural components of the cell, unlike the real-time field testing. However, by monitoring and understanding each of the underlying degradation phenomena and modifying the cell design and operating conditions, the remaining useful lifetime of the cell can be significantly prolonged, even under highly transient operating conditions. The analysis and evaluation of the mechanical, chemical and thermal factors contributing to ageing and/or early
failure of the balance-of-plant components, particularly the air compressor and the humidifier, identified the most critical ageing factors for the conditions of the intended use, i.e., inside the range extender trailer, and identified those that will need to be characterised in laboratory experiments.