Protonic Surface Conductivity and Proton Space-Charge Relaxation in Hydrated Fullerol
| Autor: | Roberto Macovez, Maria Barrio, Josep-Lluís Tamarit, Michela Romanini, Efstratia Mitsari |
|---|---|
| Přispěvatelé: | Universitat Politècnica de Catalunya. Departament de Física, Universitat Politècnica de Catalunya. GCM - Grup de Caracterització de Materials |
| Rok vydání: | 2017 |
| Předmět: |
Analytical chemistry
Dielectric relaxation Hydration 02 engineering and technology Dielectric Enginyeria dels materials [Àrees temàtiques de la UPC] 010402 general chemistry 01 natural sciences Surface conductivity Nuclear magnetic resonance Proton transport Physical and Theoretical Chemistry Física [Àrees temàtiques de la UPC] Chemistry Relaxació dielèctrica 021001 nanoscience & nanotechnology Space charge 0104 chemical sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials Dielectric spectroscopy Hidratació General Energy Melting point Anhydrous Relaxation (physics) 0210 nano-technology |
| Zdroj: | Recercat. Dipósit de la Recerca de Catalunya instname UPCommons. Portal del coneixement obert de la UPC Universitat Politècnica de Catalunya (UPC) |
| ISSN: | 1932-7455 1932-7447 |
| DOI: | 10.1021/acs.jpcc.6b12530 |
| Popis: | The ac dielectric properties of both anhydrous fullerol (C-60(OH)(24)) and hydrated fullerol with 20% water mass content are investigated by means of temperature-dependent dielectric spectroscopy. Anhydrous polycrystalline fullerol exhibits charge transport mediated by hopping of electronic charge carriers. Hydrated fullerol has a dc conductivity higher by more than a factor of 10(3) than that of the anhydrous sample due to water-induced proton transport. Four distinct dielectric relaxation processes are observed in hydrated fullerol, two of which lie in the frequency range of the electrode polarization. The fastest relaxation is only observed below the melting point of pure water and is assigned to the migration of hydrogen-bond defects in the physisorbed H2O layers. The other three processes exhibit nonmonotonous temperature dependence upon dehydration by heating. The fastest of the three is present also in the anhydrous powder, and it is assigned to a space-charge relaxation due to accumulation of electronic charge carriers at samples heterogeneities such as grain boundaries. By studying the temperature dependence of the two slower relaxations across dehydration, we identify them as separate electrode polarization effects due to distinct charge carriers, namely electrons and protons. The electronic electrode polarization is also present in pure fullerol, while the proton space-charge relaxation is only present in the hydrated material. Our findings help elucidate the hitherto puzzling observation of more than one nonmonotonous relaxation process in hydrated and water-containing systems. |
| Databáze: | OpenAIRE |
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