Efficient All Solid State Rechargeable Zinc-Air Batteries with a Spinel Type MnCo<sub>2</sub>O<sub>4</sub>/Carbon Fiber Bifunctional Electrocatalyst
Notice bibliographique
Résumé
Rechargeable zinc-air batteries (ZABs) stand out as promising candidates in the ever increasing search for sustainable energy storage devices. ZABs are inexpensive devices that exhibit relatively high energy density, safe operation with no environmental issues and long shelf life (when sealed). ZABs are composed of an electrolyte and two electrodes parallel to one another: the air electrode and the zinc electrode. The efficiency and cycle life of rechargeable ZABs are affected by the reactions that take place at the air electrode. The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) happen at the air electrode during discharge and charge, respectively. The poor kinetics for ORR/OER necessitate the use of electrocatalysts at the air electrode. Traditionally, precious metals like Pt and Ru have been used as ORR and OER catalysts, respectively, to lower the energy barrier for these reactions. However, these catalysts are rare and expensive and suffer from poor cycling stability. Transition metal oxides are inexpensive, abundant and safe alternative electrocatalyst options for air electrodes in ZABs. Mn and Co based oxides have been shown to have reasonable activities towards ORR and OER, respectively. In this work, high performance and efficient all solid state ZABs were prepared. Mn-Co mixed oxide (MnCo 2 O 4 ) was employed as the bifunctional electrocatalyst. Hydrogel electrolytes, containing polyacrylic acid (PAA), KOH and N,N’-methylenebis (acrylamide) or MBAA as the crosslinker, were used. MnCo 2 O 4 coated carbon fibers (MnCo 2 O 4 /CF) were utilized to prepare the air electrodes, with asphaltene based carbon fibers as a conductive substrate for the MnCo 2 O 4 coating. A facile one pot sonication method for coating MnCo 2 O 4 onto the CF, using an ultrasonic bath, was employed. CFs were sonicated in a mixture of 30 ml of reagent alcohol, 100 mg of NaOH, 167 mg of Mn(II) acetate (Mn(Ac) 2 or C 4 H 6 MnO 4 ) and 333 mg of Co(II) acetate (Co(Ac) 2 or C 4 H 6 CoO 4 ) for 5 h. A paste, consisting of 90 mg of MnCo 2 O 4 /CF, 5 mg of carbon black and 5 mg of PTFE (polytetrafluoroethylene) was used to prepare the air electrodes. Because all the CFs were coated with MnCo 2 O 4 and then used to prepare the air electrodes, the MnCo 2 O 4 bifunctional electrocatalyst was distributed throughout the whole thickness of the air electrode as opposed to only on the surface (which is the case for methods like electrodeposition or spray coating). Initially, different crosslinker concentrations in the hydrogel electrolytes were tested; a crosslinker concentration of 30 mM (referred to as Hydrogel-30-mM) provided the best ZAB performance. Concentrations higher than 30 mM were too viscous and stiff so the O 2 /electrocatalyst/electrolyte three phase boundary area was not sufficient for efficient ZAB performance. Concentrations less than 30 mM did not have the rheological performance of a gel polymer electrolyte. Charge/discharge battery performance at different current densities, cycling behavior (at 10 mA cm -2 ), polarization curves and power density values for MnCo 2 O 4 /CF and the benchmark Pt-RuO 2 electrocatalyst in Hydrogel-30-mM were evaluated. MnCo 2 O 4 /CF had a very efficient and stable performance, compared with that of Pt-RuO 2 . The initial and final efficiencies for MnCo 2 O 4 /CF were 62.6% and 56.1%, respectively, for 200 cycles (100 hours: 10 min charge, 5 min rest, 10 min discharge) at 10 mA cm -2 , while the initial efficiency for Pt-RuO 2 was 61.3% and the battery failed after ~100 cycles. MnCo 2 O 4 /CF also had a superior performance to that of Pt-RuO 2 in Hydrogel-30-mM, in terms of the maximum power density delivered; i.e., ~ 240 mW cm -2 for MnCo 2 O 4 /CF versus 165 mW cm -2 for Pt-RuO 2 .
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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 | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,001 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| 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 | 0,000 | 0,001 |
| 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 ».