Oxidation and Corrosion of Platinum–Nickel and Platinum–Cobalt Nanoparticles in an Aqueous Acidic Medium
Notice bibliographique
Résumé
We report on the synthesis, characterization, and corrosion behavior of randomly oriented platinum–nickel and platinum–cobalt nanoparticles (PtNi-NPs, PtCo-NPs). Unsupported and carbon-supported nanocatalysts were synthesized using the “water-in-oil” microemulsion method. X-ray diffraction (XRD) was used to examine their average crystallite size, which was 2.3 nm in both cases. The shape, size, and size distribution of the nanoparticles were evaluated using transmission electron microscopy (TEM); they were determined to be spherelike with an average size of 3.3 and 3.2 nm for PtNi-NPs and PtCo-NPs, respectively, and a narrow size distribution. Comparison of the XRD and TEM data indicated that the nanocatalysts were polycrystalline in nature. Thermogravimetric analysis (TGA) measurements were carried out to evaluate the metal loadings of the carbon-supported nanocatalysts, which were 38.1 wt % for PtNi-NPs and 40.8 wt % for PtCo-NPs. Static Density Functional Theory (DFT) calculations were performed to analyze the structures and energetics of the PtNi and PtCo systems; it was found that the presence of Ni and Co introduced ca. 8% of volume reduction, as compared to the volume of pure, bulk Pt. Cyclic voltammetry (CV) measurements at potential scan rates of 5.0 and 50.0 mV s –1 in 0.50 M aqueous H 2 SO 4 indicated that the specific surface areas ( A s ) of the PtNi-NPs and PtCo-NPs were 74.5 m 2 g Pt –1 and 33.1 m 2 g Pt –1, respectively. In situ confocal Raman spectroscopy was successfully used to monitor the formation and reduction of surface oxide layers in the submonolayer and monolayer ranges. Corrosion of the nanocatalysts was studied using anodic and cathodic potentiodynamic polarization (PDP) measurements at a very low potential scan rate of s = 0.10 mV s –1 in 0.50 M aqueous H 2 SO 4 saturated with different gases (N 2 (g), O 2 (g), or H 2 (g)). The nature of the dissolved gas had a profound impact on the corrosion characteristics of the nanoparticles. The nanocatalysts were stable in the electrolyte saturated with H 2 (g) and underwent slight corrosion in the electrolyte saturated with N 2 (g) and significant corrosion in the electrolyte saturated with O 2 (g). The carbon support was also observed to undergo corrosion and porosity changes. The degradation of the nanocatalysts was more pronounced in the case of the anodic PDP measurements than the cathodic ones. Cyclic voltammetry was employed to analyze the loss of A s of the nanocatalysts as a result of PDP measurements, and the results were found to corroborate the corrosion data. Evolution of the value of A s of the nanocatalysts in 0.50 M aqueous H 2 SO 4 outgassed using N 2 (g) was examined by recording 500 CV transients in the 0.05 V ≤ E ≤ 1.45 V range at s = 50.0 mV s –1 . It was found that in both cases this treatment resulted in a 50% reduction in A s .
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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 | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 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 ».