Novel Methodology for Ex-Situ Characterization of Catalysts in Reversal Tolerant PEM-FCs
Notice bibliographique
Résumé
To reduce damage to carbon containing components of fuel cell stacks during start-up and shutdown, extensive research has been carried out to produce reversal tolerant anodes (RTAs) using oxygen evolution reaction (OER) catalysts [1-4]. However, most of these results were obtained using resource intensive in-situ testing that suffers from long experimental times. To address this, a series of ex-situ experiments was devised to characterize the activity and durability of OER catalysts in a simulated polymer electrolyte fuel cell (PEMFC) environment. The dissolution/re-deposition mechanism of the OER catalysts were investigated using a combination of linear sweep voltammetry and potential stepping experiments within the normal operating range of PEMFCs (0 V to 1.2 V vs RHE). During normal fuel cell operation, IrO2 based catalysts form soluble Ir3+ species as an intermediate between metallic Ir and IrO2. Ir3+ ions can be washed out of the cell which diminishes the reversal tolerance of the anode. After our electrochemical testing, dissolved Ir3+ concentrations in the electrolyte were determined using the inductively coupled plasma mass spectrometry (ICP-MS) method. An in-line ICP-MS technique was previously used by Cherevko et al. to determine the potential resolved dissolution in real time [5]. To validate the ex-situ accelerated testing protocol, experimental reversal tolerance tests were carried out at four different temperatures (20, 40, 60 and 80 °C) and the results showed an increase in the concentration of Ir detected in the electrolyte solutions (Fig. 1). Additionally, different OER catalysts were tested and the results were correlated with in-situ reversal tolerance tests. The effect of OER catalyst structure and support interactions on catalyst stability was investigated by a combination of surface analytical and electrochemical techniques. The surface analysis revealed that there was dissolution and re-deposition occurring during accelerated degradation testing. SEM-EDX imaging of the catalyst layer after testing, showed relocation of the OER catalyst to the cracks of the gas diffusion layer supporting a microporous layer (GDL/MPL) substrate (Fig. 1). Taniguchi A, Akita T, Yasuda K, Miyazaki Y (2004) Analysis of electrocatalyst degradation in PEMFC caused by cell reversal during fuel starvation. J Power Sources 130:42–49. doi: 10.1016/j.jpowsour.2003.12.035 Ralph TR, Hudson S, Wilkinson DP (2006) Electrocatalyst stability in PEMFCs and the role of fuel starvation and cell reversal tolerant anodes. ECS Trans 1:67–84. doi: 10.1149/1.2214545 Mandal P, Litster S (2016) Investigation and mitigation of degradation in polymer electrolyte fuel cell due to cell reversal using oxygen evolution catalyst. Meet Abstr MA2016-01:1419–1419. Jung J, Park B, Kim J (2012) Durability test with fuel starvation using a Pt/CNF catalyst in PEMFC. Nanoscale Res Lett 7:34. doi: 10.1186/1556-276X-7-34 Cherevko S, Geiger S, Kasian O, Kulyk N, Grote J-P, Savan A, Shrestha BR, Merzlikin S, Breitbach B, Ludwig A, Mayrhofer KJJ (2016) Oxygen and hydrogen evolution reactions on Ru, RuO2, Ir, and IrO2 thin film electrodes in acidic and alkaline electrolytes: A comparative study on activity and stability. Catalysis Today 262:170–180. doi: 10.1016/j.cattod.2015.08.014 Figure 1. Images: backscattered electron (BSE) detector images at 500x magnification of OER catalysts deposited on a GDL/MPL (a) before ex-situ testing and (b) after ex-situ testing. The bright dots were confirmed by EDX to contain Ir atoms. Bar graph: Electrolyte Ir concentration after accelerated degradation protocol. Performed in a flooded, N2 purged, 0.09 M H2SO4, three electrode cell for 30,000 cycles from 0.05 V to 1.2 V vs. RHE with a 1 s hold at each potential. OER catalysts were prepared by sonication in 2-propanol overnight and then 400 μg deposited dropwise onto the GDL/MPL substrate. Three trials were carried at each temperature and the error bars are the standard error of the trials. Figure 1
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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) | 0,001 | 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 | 0,001 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,001 |
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 ».