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

Journal Article · Thu Aug 07 04:00:00 EDT 2014 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4891722· OSTI ID:22419998

Wang, Juan; Zhao, Kongshuang ^[1]; Wu, Lixin ^[2]

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1. College of Chemistry, Beijing Normal University, Beijing 100875 (China)
2. State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012 (China)

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.

• OSTI ID: 22419998
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 5 Vol. 141; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

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