Earth-Abundant Redox Couples Using Durable Boron Doped Diamond Electrodes: Beyond Vanadium Redox Couples

In this study, boron doped diamond (BDD) is utilized as a redox flow battery (RFB) electrode, demonstrating its capability with several low-cost redox couples for the first time. Active species cost, electrode corrosion, energy density, and power density are the current issues hindering the widespread adoption of RFBs. Several high-potential and low-cost redox couples, including Ce3+/Ce4+ and Mn2+/Mn3+, are shown to exhibit low overpotentials, high efficiency, and good cyclability on BDD electrodes. Using the Ce3+/Ce4+ redox couple, a formal potential of 1.67 V vs. SHE and a peak separation of 288 mV during cyclic voltammetry was obtained. Low-cost redox species significantly decrease RFB system cost while high potentials increase energy and power density. Demonstrated here, high potentials cannot be supported by traditional carbon-based RFB electrodes due to significant corrosion and gas evolution; however, the inherent properties of BDD negate this effect. This study exhibits the potential of BDD, as an alternative to traditional carbon-based electrodes, to enable a long cycle life, at high coulombic efficiencies, and with high-potential and low-cost redox couples.