Novel Epoxy-Free Imaging of the Proton Exchange Membrane Fuel Cell Components and Microstructure Degradation By Transmission Electron Microscopy
Notice bibliographique
Résumé
Performance, durability, and efficiency limitations of proton exchange membrane fuel cells (PEMFCs), as one of the alternative clean energy resources, has been hindering the widespread adoption of these devices. Improving those parameters is closely entangled with identifying the degradation mechanism of each component in the electrodes i.e., catalyst – commonly platinum nanoparticles, catalyst support – carbon, and the ion conductive polymer – ionomer, as well as the effects that degradation can have on the porous network of the electrodes[1]. Degradation during typical automotive operation protocols like startup/shut down (SUSD)[2,3] is of a special interest. Therefore, it is essential to observe the changes of the microstructure, as whole, and each individual component’s response to the working condition, in order to understand degradation mechanisms and devise degradation mitigation strategies. Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) in conjunction with energy dispersive spectroscopy (EDS) have proven to be valuable tools in unravelling the complex changes of the microstructure and understanding of the degradation mechanisms[4]. Moreover, correlating the numerical microstructural descriptors, extracted by quantification of the TEM and EDS results, with the visual observations helped the research community to draw a connection between the degradation and microstructural changes[5]. However, the conventionally prepared TEM samples by slicing (microtomy) an epoxy-embedded piece of a catalyst coated membrane (CCM) have limitations in observing carbon and ionomer, and distinguishing them from each other and from the epoxy. Partial epoxy-embedding showed very promising results regarding distinguishing carbon from ionomer in selected regions of the CCM[6]. However, not a full CCM was observed. Therefore, we report for the first time, an epoxy-free microtomy approach for a whole CCM, successfully implemented on a fresh and degraded cathode layer of beginning-of-life (BOL) and SUSD samples, respectively. Electrochemical characterization of the samples presented here are discussed in previous publication[2]. The Pt catalyst, carbon, ionomer and porous network of the cathodes were clearly observable and distinguishable in both BOL and SUSD samples using high-resolution TEM and 3D electron tomography-TEM (ET-TEM) imaging. The microstructural comparison revealed the changes in Pt particles distribution – moving into the ionomer network rather than sitting on and inside the carbon support, disintegration of corroded carbon and dispersion of broken-off graphitic carbon pieces in the ionomer, and alteration of the ionomer network – formation of more ionomer filaments. In addition, ET-TEM of the BOL and SUSD samples confirmed the presence of Pt particles inside the amorphous core of the carbon particle and their migration during SUSD operation, respectively. Finally, the visual results were correlated with the microstructural descriptors quantified using our proprietary quantification technique. The numerical microstructure properties corroborated the observations that was made based on the TEM images observations. Therefore, implementation of whole-CCM-epoxy-free microtomy technique can be considered as a novel method in aiding the research community in understanding the degradation mechanism and microstructural properties alteration. References: [1] A. P. Soleymani, L. R. Parent, J. Jankovic, Adv. Funct. Mater. 2022, 32, 2105188. [2] C. Wang, M. Ricketts, A. P. Soleymani, J. Jankovic, J. Waldecker, J. Chen, C. Xu, J. Electrochem. Soc. 2021, 168, 034503. [3] C. Wang, M. Ricketts, A. P. Soleymani, J. Jankovic, J. Waldecker, J. Chen, J. Electrochem. Soc. 2021, 168, 044507. [4] A. P. Soleymani, J. Chen, C. Wang, M. Ricketts, S. Papasavva, J. Waldecker, J. Jankovic, in ECS Meet. Abstr., IOP Publishing, 2021, p. 1069. [5] A. Kneer, J. Jankovic, D. Susac, A. Putz, N. Wagner, M. Sabharwal, M. Secanell, J. Electrochem. Soc. 2018, 165, F3241. [6] K. More, Microstructural Characterization of Polymer Electrolyte Membrane Fuel Cell (PEMFC) Membrane Electrode Assemblies (MEAs), 2005.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».