A 3D-Multiphysics Degradation model for PEM Fuel Cells with Focus on Platinum Dissolution

The de-carbonisation of power sector (transportation,stationary power generators, etc.) is one of the key areas on which major engineering efforts are being focused. Fuel cells (FCs) are electrochemical devices capable of directly converting the energy of reactants (usually hydrogen and oxygen) into electrical current (direct current, DC) and, for this reason, are among the most promising technologies for reducing pollutant emissions. Current efforts in fuel cell development are focused on predicting how they degrade over time and optimizing the materials used in order to extend their useful life-time. The majority of the model proposed are zero-dimensional, not taking into account all the possible in-homogeneity among the cell. For this reason, the focus of this work is to develop an engineering work-flow capable to assess degradation, while defining all the necessary model reductions, with the aim of applying it to the study of industrial-scale cells. In this regard, some of the main mechanisms responsible for fuel cell degradation are discussed, providing a model capable of quantifying the reduction of platinum within the cell over time. Crucial to understanding how different components degrade over time is to consider how the various parameters that influence the specific degradation mechanism under investigation vary across the cell. Therefore, this work began with the development of a zero-dimensional model, based on the work made by Schneider et al., and then moved on to the implementation of the various degradation mechanisms in a fully coupled 3D model. The degradation model analyzed, based on the work carried out by Schneider et al. [1], takes into account the reduction in the quantity of platinum linked to three main mechanisms: platinum dissolution, platinum particle growth (also known as Ostwald ripening) and platinum ion migration towards the membrane. In the first part of this work, we implemented the 0D model related to these degradation mechanisms, analyzing the stressor that most influence the reduction of platinum within the catalytic layer. We then implemented the same physics into a 3D model with a simplified straight-channel geometry. In the final part of this work, the same methodology was applied to a more complex geometry consisting of a multitude of serpentine channels, in order to elucidate how spatial variations in key degradation parameters give rise to non-uniform degradation patterns across the cell.