Synthesis and Performance Evaluation of Exfoliated Graphene Nanoplatelet Hydrogels As Electrodes for Supercapacitors
Notice bibliographique
Résumé
Graphene is an excellent material because of its high electrical conductivity, high surface area, and superior mechanical properties. Stable dispersions of graphene nanoplatelets (GNPs) can be only achieved in organic solvents while in polar solvents the GNPs tend to agglomerate. Therefore, covalent and non-covalent functionalization of the GNP, or the use of surfactants, is required to formulate stable dispersions. Unlike GNP, Graphene oxide (GO) can be readily dispersed in aqueous media because of the hydrophilic oxygen groups on the basal plane and edges. Consequently, GO has amphiphilic material characteristics like a surfactant, and we use it as a dispersing agent for GNP in aqueous solutions. In this work, we formulate highly-concentrated aqueous GO/GNP dispersions (5 mg/ml to 25 mg/ml). The stability of these dispersions mainly depends on the pH, concentrations of GO/GNP and lateral dimensions of the flakes. Stable dispersions are used to synthesize graphene hydrogels which are usually made from reduced graphene oxide (rGO), which is considerably more expensive than GNP obtained from mechanical/thermal exfoliation. Graphene hydrogels are a self-assembled microporous structure that incorporate a liquid phase. The graphene hydrogel matrix has a very high surface area, along with high electronic conductivity, which makes it a very suitable material for supercapacitor applications. The graphene hydrogels that we prepare from GNP, containing a small fraction of GO, are characterized by scanning electron microscopy, electrical conductivity measurements, X-ray diffraction, and Raman spectroscopy. The results indicate that a minimum GO/GNP ratio of 0.1 is required to stabilize the GNP flakes. The three-dimensional self-assembly is promoted due to the reduction of GO. The GNP hydrogels have better mechanical stability compared to a conventional rGO hydrogel; a 50 mg freeze-dried sample can sustain a load of 200 g of weight. A flexible supercapacitor is prepared from the GNP hydrogels. In detail, the symmetrical electrodes are prepared by pressing a 1 mm thick slice of hydrogel onto a carbon cloth current collector and two of these electrodes are separated by a filter paper soaked in a 2 M H 2 SO 4 electrolyte. The supercapacitor is characterized by cyclic voltammetry, electrical impedance spectroscopy as well as galvanostatic charge and discharge measurements. The specific capacitance obtained at 1 A/g is 187 F/g, which is around 30% higher than that of comparable supercapacitor made from rGO hydrogels. Additionally, the specific capacitance and the coulombic efficiency at 10 A/g remains at almost 100% of the initial values, even after 3000 cycles. Figure 1
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 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 | 0,002 | 0,002 |
| 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 tête enseignante, 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 ».