A Pore Scale Model for the Transport Phenomena in the Catalyst Layer of a PEM Fuel Cell
Bibliographic record
Abstract
In a proton exchange membrane fuel cell (PEMFC), the catalyst layer is a porous medium made of carbon-supported catalysts and solid electrolyte, and has a thickness in the order of 10 μm. Within this layer, complex transport phenomena take place: transport of charged species (H+, electrons and ionic radicals), non-charged species (gaseous H2O, O2, H2, N2 and liquid water) and heat transfer occur in their own pathways. Furthermore, phase change of water and physiochemical/electrochemical reactions also take place on phase boundaries. These transport process take place in an intertwined network of materials having characteristic length scale ranging from nano-meters to micro-meters. The objective of the present study is two-fold, i.e., to develop a rigorous theoretical framework based on which the transport in the micro-structural level can be modelled, and to construct a pore scale model that resolves the geometry of the phases (carbon, ionomer and gas pores) for which direct numerical simulation can be performed. The theoretical framework is developed by employing the volume-averaging techniques for multi-phase porous media. The complete set of the conservation equations for all species in all phases are derived and every interfacial transport is accounted. The problem of model closure on the terms in the transport equations is addressed by the pore-scale model reported in the present study. A 3-D pore-scale model is constructed by a solid model that consists of packing spherical carbon particles and simulated ionomer coating on these carbon aggregates. The index system of the pore-scale model allows easy identification of volumetric pathway, interfaces and triple phase boundaries. The transport of charged and non-charged species is simulated by solving the equations based on first principle in the entire representative element volume (REV) domain. The computational domain contains typically several million cells and a parallelized, iterative solver, GMRES, is employed to solve the coupled transport with complex geometries. Computational results based on the pore-scale model show that the effective transport properties of the species are strongly affected by the micro-structure, e.g. morphology and phase-connectivity. Further simulations and investigation on the coupling effects of the transport are underway. Combination of the proposed theoretical framework and pore-scale model will lay a foundation for the construction of multi-scale modelling of the PEMFC catalyst layer. On the one hand, the pore-scale model helps close the macroscopic volume-averaged equations in the framework. On the other hand, the pore-scale model provides a platform to include microscopic or atomistic simulations.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".