Notice bibliographique
Résumé
Pt is a widely used catalyst for fuel cells in industry, but the irreversibility of the oxygen reduction reaction (ORR) restricts its efficiency and incurs about 40% of all irreversible energy losses1. Furthermore, the dissolution of Pt degrades the catalyst and limits its lifetime. Pt oxide is known to play a role in promoting the dissolution2 and is thought to degrade the performance of the ORR. Even though studies have been done for many years, the details of the oxide structure and the mechanism of oxide formation and reduction are still not fully resolved. In the case of the kinetics, most work has been directed at the oxide formation, and the reduction kinetics have been relatively neglected. We report here kinetic studies on the Pt oxide reduction on polycrystalline Pt by cyclic voltammetry and various potential programs that combine sweep and hold periods. Differential-equation-based models were investigated to simulate the oxide reduction and estimate kinetic parameters. The simplest sweep-hold method involves preparing the surface with potential sweeps and then holding the potential at selected potentials. Constant potential is typically better for quantitative analysis of kinetics since the rate constants are fixed. Compared to conventional large potential steps, the sweep preparation enables the initial conditions to be closely controlled, and the double-layer charging is less. Adding different negative-going sweeps after identical sweep-hold experiments allows for study of sweep rate dependence under identical coverage and potential initial conditions, which is not the case for regular cyclic voltammetry at different sweep rates. Most simple mechanisms are based on rate laws in which the rates and current at time t are only dependent on the coverages and potential at time t, and not on the history of how those coverages were prepared. In contrast, rates for nucleation-and-growth type mechanisms can depend on the history. Since the oxidized surface is a restructured surface, different histories may also produced different 3-D structures at the same coverage. By varying the preparation step to produce the same coverage at the same potential but with different histories, evidence was found that the reduction peak position and shape only depend on oxide coverage and potential, and not on the history. The results are presented and modelled with a simple adsorption mechanism, which gives reasonable agreement with experiment. Refinement will use the idea that the relationship between coverage and available Pt sites may not be linear3. References [1] S.G. Rinaldo, W. Lee, J. Stumper and M. Eikerling, Electrocatalysis, (2014) 5:262-272. [2] A.A. Topalov, I. Katsounaros, M. Auinger, S. Cherevko, J.C. Meier, S.O. Klemm, K.J.J Mayrhofer, Angew. Chem. Int. Ed. Engl. (2012) 51:12613–5. [3] P.K. Dahlstrøm, D.A. Harrington and F. Seland, Electrochim. Acta, (2012) 82:550-557.
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 | 0,001 |
| 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 | 0,001 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 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 ».