Accessible Surface Area in Porous Carbon Electrodes and Its Impact on Redox Flow Battery Performance

摘要

Carbon-fiber electrodes exhibit many desirable material properties including conductivity, porosity, and chemical stability, and, accordingly, are employed in a range of electrochemical technologies. Such electrodes are particularly important in redox flow battery (RFB) systems, as they serve multiple critical functions including providing surface area for electrochemical reactions, distributing liquid electrolytes, and conducting electrons and heat. While commercially available materials possess suitable permeability and conductivity, the performance of pristine substrates is limited, thus oxidative treatment prior to use is common practice. Partial oxidation of the electrode surface has been shown to add a range of oxygen functional groups, which improve hydrophilicity and, in some cases, catalyze redox reactions, as well as to increase available surface area for the electrochemical reactions. Both effects are posited to improve electrode performance but their relative importance and effectiveness remains unclear.