Kinetic Modeling of Chemical Degradation Phenomena in Fuel Cell Ionomers
Bibliographic record
Abstract
A kinetic model has been developed to describe the chemical degradation of Nafion-type polymer electrolyte membranes. The model accounts for pathways of radical formation and consumption along with mechanisms of ionomer degradation through radical attack. Systematic simplifications on the set of model equations lead to analytical expressions for concentration of aggressive hydroxyl radical as a function of initial iron content and hydrogen peroxide concentration. The ionomer degradation model employs a coarse-grained structure of Nafion ionomer. . It distinguishes units corresponding to head groups and trunk segments of sidechains. The backbone segment between two sidechains is the third unit considered in the degradation model. A set of differential equations is formulated to describe the consumption of these units and determine the associated rate of fluorine loss and the change in the ion exchange capacity (IEC). A parametric study was performed to study the impact of different degradation mechanisms, degradation conditions, and chemistries of the PFSA on fluorine loss and IEC change. The rate constants of degradation processes are found through comparison with the experimental degradation data. Results will be discussed in view a structural stabilization of PEMs and the mitigation of chemical degradation.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".