Characterization of doping atoms (Ta, Nb) in advanced PEM fuel cell supports and catalysts as well as of the surface-solvent interaction of laser-generated Pt nanoparticles : A XAFS study
Pourquoi ce travail est dans la base
Une base qui oublie comment elle a trouvé un travail ne peut pas être vérifiée. Voici les voies qui ont admis celui-ci.
Notice bibliographique
Résumé
PEM fuel cells are an interesting energy source for mobile applications. Efforts to improve their weaknesses cost, performance, and durability include improving the catalysts’ supports. Encouraging approaches are C-TiO<sub>2</sub> hybrid and core-shell supports whereas titanium dioxide is commonly doped to increase its electric conductivity.<br /> In this thesis I studied the impact of Ta-/Nb- co-doping on a TiO<sub>2</sub> nano-support, C-TiO<sub>2</sub> hybrid/core-shell supports made by adding two kinds of carbon black and a Pt-TiO<sub>2</sub> catalyst-support unit. XANES results show that both dopants replaced Ti atoms and are statistically distributed in their respective TiO<sub>2</sub> host structure (which is either predominantly rutile or anatase). There is also evidence of interaction between these dopants and both the carbon supports as well as Pt catalyst, most likely via bridging oxygen atoms. EXAFS analysis reveals that Nb incorporation did distort the TiO<sub>2</sub> host structure of at least one sample to a greater extent compared to Ta incorporation. The core-shell support displays the highest degree of disorder and smallest particle size, which is most likely correlated.<br /> Reduction/oxidation experiments show that Pt atoms in PtPd nano-catalysts supported on C-TiO<sub>2</sub> hybrid nano-supports have a low affinity for oxidation and are easily reduced.<br /> Pulsed laser ablation in liquid (PLAL) has proven its usefulness as a nanoparticle (NP) synthesis method alternative to traditional chemical reduction methods.<br /> Additive-free Pt NPs were synthesized by PLAL and their interaction characterized in situ with H<sub>2</sub>O, a sodium phosphate buffer and sodium citrate as well as a TiO<sub>2</sub> support. XANES results indicate that the respective NP-solvent interaction varies in strength. The ions added ex situ diffuse through the particles’ electric double layer and interact electrostatically with the Stern plane. Consequently, these ions weaken the interaction of the functional OH-groups which are bound to the partially oxidized platinum surfaces and cause their partial reduction. Comparing XANES/EXAFS spectra of laser-generated with wet-chemically synthesized Pt NPs indicate different types of Pt-O bonds: a Pt(IV)O<sub>2</sub>-type in case of wet-chemical and a Pt(II)O-type in case of laser-generated NPs. A comparison of unsupported laser-generated platinum NPs in H<sub>2</sub>O with TiO<sub>2</sub>-supported ones shows no whiteline intensity differences and also an identical number of Pt-O bonds in both cases. This suggests that in the deposition process at least part of the double layer coating stays intact and that the ligand-free particle properties are preserved.
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.
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| 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 | 0,000 | 0,000 |
| 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 découle