Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6616760 | Electrochimica Acta | 2013 | 8 Pages |
Abstract
The outward diffusion equation of the instantaneously released ion in pores of a porous layer was derived theoretically, and then applied for the study of oxygen ion diffusion in porous Fe which was generated by fast electrochemical reduction of solid Fe2O3 in molten CaCl2. The solid cathode was constructed by filling mixed Fe/Fe2O3 powders (8:1 in mass ratio) into cylindrical cavities in a Mo foil substrate. This fabricated mini porous electrode was subjected to the double-potential treatment with selected potentials according to the cyclic voltammetry (CVs) of Fe2O3. The lower potential of â0.7Â V (vs. quartz sealed Ag/AgCl) enabled fast reduction of solid Fe2O3, and instantaneous release of O2â ions into the pores of the generated porous Fe. During the standing time at â0.7Â V, outward O2â diffusion occurred, and the amount of O2â remaining in the porous electrode was determined by re-oxidation at a potential of 0.16Â V. The experimental outward diffusion of O2â was in good accord with the theoretical equation, consequently, the diffusion coefficients of O2â in CaCl2 contained in porous Fe were evaluated as 8.2Â ÃÂ 10â6, 9.1Â ÃÂ 10â6 and 1.0Â ÃÂ 10â5Â cm2Â sâ1 at 1108, 1123 and 1138Â K respectively. These data followed the Arrhenius' equation with diffusion activation energy of about 67.8Â kJÂ molâ1. The whole work can provide a simple method for the study of diffusion in a porous electrode, and the designed ultrafast deoxidation of solid Fe2O3 may be also helpful to the present effort in developing iron metallurgy by molten salt electrolysis.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Chemical Engineering (General)
Authors
Haiping Gao, Xianbo Jin, Siwei Zou, Fengzi Ling, Junjun Peng, Zhiyong Wang, George Z. Chen,