Optimization and Fabrication of Porous Carbon Electrodes for Fe/Cr Redox Flow Cells

摘要

The scope of this program was limited to negative electrode development for the NASA chromous/ferric Redox battery. The effects of substrate material, gold/lead catalyst composition and loading, and catalyzation procedures on the performance of the chromium electrode were investigated. Three alteranative catalyst systems were also examined, and 1/3 square foot size electrodes were fabricated and delivered to NASA at the conclusion of the program. The significant findings were as follows: (1) In a preliminary examination the felt substrate appeared to have considerable influence on the performance of the negative electrode. The reaction level, both for hydrogen evolution and the Cr exp 3+ /Cr exp 2+ Redox reaction, declined with increasing felt processing temperature over the range of 1250 exp 0 C to 2300 exp 0 C. In terms of charging efficiency, a felt processed at 1630 exp 0 C gave the highest Cr exp 2+ :H sub 2 ratio, in half cell cyclic voltammetry testing. (2) The reaction levels, both for hydrogen evolution and the Cr exp 3+ /Cr exp 2+ Redox reaction, were found to increase with increasing gold loading over the range of 3 to 50 g/cm sub 2 . There were many large deviations from the relationship between the CR exp 3+ /Cr exp 2+ Redox reaction level and simple gold loading, however. It was found that many of the deviations could be accounted for by variations in the particular size (and surface area) of the gold deposits as determined by transmission electron microscopy. (3) The alcohol-assisted gold deposition process was scaled up, using two variations of a simple felt immersion process, without substantial change in performance. These results although consistent, appeared to be different from results obtained with electrodes prepared by NASA Lewis. (ERA citation 08:031930)