| Summary: | 碩士 === 輔仁大學 === 化學系 === 96 === Vanadium redox flow cell is very powerful in large-scale energy storage, because it presents high capacity, excellent cycle life, fast response, and large open circuit voltage, etc. Although the overall cell performance depends on several factors, the fundamental knowledge of negative and positive electrode reactions are still importance to be optimized the electrolytes.
In this study, we use graphite/glassy carbon as composite electrode of vanadium redox flow cell, and vanadium ion solution were prepared in 1.0M~4.0M H2SO4 as electrolyte. We determined the potential windows of graphite and glassy carbon electrode from voltammograms and Tafel plots. The V(IV)/V(V) and V(II)/V(III) redox reactions in various concentration of sulfuric acid solution had been investigated by cyclic voltammetry and A.C. impedance to study the kinetics between vanadium ion and electrode. Otherwise, we also used spectroelectrochemical method (In-situ UV-Vis. and Ex-situ Raman) to discuss the mechanism of V(IV)/V(V) and V(II)/V(III) redox reactions. The mechanisms were indicated that performances of positive and negative electrodes are corresponded to the concentration of proton, so that we can prepare the concentration of sulfuric acid and vanadium both in 2.0M as the electrolyte of test cell.
Three types graphite/glassy carbon composite electrodes were used to test by single cell. And the results indicate that graphite/glassy carbon composite electrodes can promote the efficiency of test cell and total efficiency is from 30%~40% up to 50%~60%.
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