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Title: Electrical transport properties and interaction of heteropolyacid in N,N-dimethylformamide by dielectric spectroscopy

We present a dielectric spectroscopy study on binary electrolyte solutions composed of N,N-Dimethylformamide (DMF) and heteropolyacid (HPA). The HPA is composed of H{sup +} and Keggin polyoxometalate anion, [XW{sub 12}O{sub 40}]{sup n−}(X = P, Si, with n = 3, 4). Conductivity was used to calculate the transport parameters such as diffusion coefficient and hydrodynamic radius of polyoxometalate (POM) anions. The hydrodynamic radius of P{sub 12}W{sub 40}{sup 3−} and Si{sub 12}W{sub 40}{sup 4−} are 5.552 Å and 5.526 Å, respectively, indicating that these POM anions remain unsolvated in DMF. The temperature dependences of conductivity obeyed the Arrhenius equation, suggesting that the activation energy of proton conduction process is independent with temperature. The calculated activation energy shows that the conduction process follows Grotthuss mechanism, i.e., proton is transported by hydrogen bond between DMF molecules. One dielectric relaxation observed around 10 MHz is considered to be associated with the POM-DMFH{sup +} ion-pairs formed by POM and protonated DMF. The interaction between anion and cation in POM-DMFH{sup +} ion-pairs are explained theoretically based on the Bruggeman's mixture theories and dipole rotation model. From this, the distance between POM and DMFH{sup +} are estimated as about 1.1 nm.
Authors:
;  [1] ;  [2]
  1. College of Chemistry, Beijing Normal University, Beijing 100875 (China)
  2. State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012 (China)
Publication Date:
OSTI Identifier:
22419998
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 5; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACTIVATION ENERGY; ANIONS; ARRHENIUS EQUATION; DIELECTRIC MATERIALS; DIFFUSION; DIPOLES; ELECTROLYTES; INTERACTIONS; ION PAIRS; MHZ RANGE; MOLECULES; PROTONS; ROTATION; SOLUTIONS; SPECTROSCOPY; TEMPERATURE DEPENDENCE