Investigation of mesoscopic degradation phenomena in fuel cells
Bibliographic record
Abstract
Commercialization of fuel cell technology for heavy-duty bus application relies on the durability of the components used in fuel cell stack.The durability of polymer electrolyte fuel cell (PEFC) is affected mainly by degradation of catalyst coated membrane (CCM).CCM consist of Pt/C based catalyst layers coated on both sides of PFSA ionomer membrane.In an operating fuel cell, PFSA ionomer membrane degrades under the action of combined chemical/mechanical stresses and Pt/C electrocatalyst degrades due to high voltage excursions.In this thesis, the most relevant approach to understand PEFC degradation during its operation is carried out by employing in situ stressors.The mesoscale morphology and affected physico-chemical properties of fuel cells are investigated with the commonly encountered stressors.Firstly, the mesoscale morphology and its relation to physico-chemical properties of the ionomer membrane under the influence of an accelerated stress test (AST) featuring in situ coupled chemical/mechanical stresses are investigated.The role of combined chemical/mechanical stresses on the ionomer membrane mesoscale morphology and structure is studied using transmission electron microscope (TEM) and thermogravimetric analysis.It is determined that the microstructure of PFSA ionomer membrane is strongly influenced by the degradation history of PEFC.The mesoscale morphological degradation is found to precisely influence the water uptake of the ionomer membrane.The effects realized through chemical and mechanical stressors in coupled and decoupled forms are evaluated through the mesoscale morphology and physico-chemical property studies.Secondly, cathode catalyst layer (CCL) subjected to a voltage cycling AST to mimic the high voltage excursions is studied.It is found that the CCL degradation led to the inhomogeneous distribution of solid and pore phases.The change in the CCL structure accompanied by the platinum agglomeration, carbon corrosion and spatial redistribution of ionomer with voltage cycling is investigated using TEM micrographs with phase sensitive mapping.The observed degradation effects of CCL through the agglomerated and dissolved platinum, corroded carbon, spatially redistributed ionomer, and compacted solids revealed the underlying mechanisms of activation and mass transport losses.Overall, a fundamental understanding of degradation mechanisms in CCM components at mesoscale is achieved from in situ fuel cell testing, which is of particular interest in commercializing and developing durable fuel cells.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".