Abstract
In this study, we developed a novel cerium/ascorbic acid/iodine active species to design a redox flow battery (RFB), in which the cerium nitrate hexahydrate [Ce(NO3)3·6H2O] was used as a positive Ce3+/Ce4+ ion pair, and the potassium iodate (KIO3) containing ascorbic acid was used as a negative I2/I− ion pair. In order to improve the electrochemical activity and to avoid cross-contamination of the redox pair ions, the electroless plating and sol–gel method were applied to modify the carbon paper electrode and the Nafion 117 membrane. The electrocatalytic and electrochemical properties of the composite electrode using methanesulfonic acid as a supporting electrolyte were assessed using the cyclic voltammetry (CV) test. The results showed that the Ce (III)/Ce (IV) active species presented a symmetric oxidation/reduction current ratio (1.09) on the C–TiO2–PdO composite electrode. Adding a constant amount of ascorbic acid to the iodine solution led to a good reversible oxidation/reduction reaction. Therefore, a novel Ce/ascorbic acid/I RFB was developed with C–TiO2–PdO composite electrodes and modified Nafion 117–SiO2–SO3H membrane using the staggered-type flow channel, of which the energy efficiency (EE%) can reach about 72%. The Ce/ascorbic acid/I active species can greatly reduce the electrolyte cost compared to the all-vanadium redox flow battery system, and it therefore has greater development potential.
Highlights
Electrochemical energy storage technology has been developed for many energy storage methods over recent years
We found that the C–TiO2 –CoP and C–TiO2 –PdO composite electrodes synthesized by the sol–gel process and electroless plating method can greatly improve the voltage efficiency of the redox flow battery (RFB) for non-vanadium electrolytes such as iodide and iron salts [13,16]
We fabricated a series of composite electrodes including carbon paper–titanium dioxide (C–TiO2 ), carbon paper–palladium oxide (C–PdO), and carbon paper–titanium dioxide
Summary
Electrochemical energy storage technology has been developed for many energy storage methods over recent years. The development of the redox flow battery (RFB) has received the most attention. The RFB has been developed for large-scale energy storage systems (KWh–MWh) during the last decade to address the power instability of renewable energy resources (e.g., wind power and solar power) because of climate change. RFBs have been regarded as suitable for large-scale energy storage because of their modular design, good scalability, flexible operation, high storage capacity and efficiency, long operating life, safety, and environmentally friendly properties [1,2,3,4,5].
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