Electrochemistry of halogen electrodes in propylene carbonate
In this study, the electrochemical behavior of halogen/halide electrodes has been investigated. Included in this work are a study of the stability of propylene carbonate with respect to elemental chlorine, bromine, and iodine; an investigation of the solubility and conductivity of halogens and halide salts; and the determination of thermodynamic and kinetic characteristics of the iodide/triiodide/iodine couple. In the case of iodine, the equilibrium constant of the disproportionation reaction at 25/sup 0/C was determined to be 0.85. Gas chromatography analysis showed that chlorine attacks even dried, distilled PC (less than 7 ppM water), and that the extent of the reaction increases with increasing water content of the solvent. However, solutions of iodine in PC are stable for several months. Conductivity experiments were performed to determine the extent of ion-pair formation of KI and KBr in PC. In addition, the conductivity of these solutions was measured as a function of the concentration of the corresponding halogen. Increased conductivity was noted for each solution, and a maximum was observed for equimolar iodide and iodine concentrations. Cyclic voltammograms of KI in supported (KAsF/sub 6/) propylene carbonate show two anodic peaks. To characterize the voltammograms, the following sequence of reactions is proposed: (1) 3I/sup -/ ..-->.. I/sub 3//sup -/ + 2e/sup -/, and (2) 2I/sub 3//sup -/ ..-->.. 3I/sub 2/ + 2e/sup -/. The validity of this mechanism was tested in an optically transparent thin layer cell by performing simultaneous cyclic voltammetry and uv-visible spectroscopy at a narrow mesh gold working electrode. The sequence of formation and disappearance of triiodide and iodine according to (1) and (2) was confirmed by the spectral scans repeated at 30 second intervals. A transport model for the simulation of the voltammograms was developed. The results indicate that reaction (1) is kinetically inhibited while reaction (2) is reversible.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5911678
- Report Number(s):
- LBL-18335; ON: DE85008452
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products. Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
25 ENERGY STORAGE
BROMINE
ORGANIC SOLVENTS
SOLUBILITY
CHLORINE
HALOGENS
ELECTROCHEMISTRY
IODINE
STABILITY
POTASSIUM BROMIDES
VOLTAMETRY
POTASSIUM IODIDES
CARBONATES
COMPUTER CODES
D CODES
ELECTRIC CONDUCTIVITY
ELECTRODES
GAS CHROMATOGRAPHY
IONIC CONDUCTIVITY
KINETICS
O CODES
P CODES
SIMULATION
THERMODYNAMICS
ALKALI METAL COMPOUNDS
BROMIDES
BROMINE COMPOUNDS
CARBON COMPOUNDS
CHEMISTRY
CHROMATOGRAPHY
ELECTRICAL PROPERTIES
ELEMENTS
HALIDES
HALOGEN COMPOUNDS
INORGANIC PHOSPHORS
IODIDES
IODINE COMPOUNDS
NONMETALS
OXYGEN COMPOUNDS
PHOSPHORS
PHYSICAL PROPERTIES
POTASSIUM COMPOUNDS
SEPARATION PROCESSES
SOLVENTS
400400* - Electrochemistry
250903 - Energy Storage- Batteries- Materials
Components
& Auxiliaries