Zirconium boride as a novel negative catalyst for vanadium redox flow battery

Abstract Poor hydrophilicity and low electrochemical activity of carbon-based electrode materials limit the wide application of vanadium redox flow battery (VRFB). The electrochemical properties of electrodes are generally optimized by acid treatment, heat treatment or the introduction of catalysts. Nowadays, there are mainly three types of catalysts for VRFB, including metal, metal oxide and carbon-based materials. In this work, the idea of metal boride as a catalyst for VRFB is firstly proposed because of high electrical conductivity, good stability, strongcorrosion resistance, and special physical and chemical properties. In this study, nano ZrB2 is used firstly as a new type of catalyst for V3+/V2+ redox pair. The results display that ZrB2 exhibits excellent electrochemical activity and reversibility in V3+/V2+ redox process. This is because nano ZrB2 has certain catalytic activity and excellent electrical conductivity, improving charge transfer dynamics. Furthermore, it has a large specific surface area, providing more active sites. At 40–120 mA cm−2, the discharge capacity and energy efficiency of ZrB2 modified cell are higher than that of pristine cell. Energy efficiency of ZrB2 cell (72.96%) is 5.75% higher than that of pristine cell (67.21%) at 120 mA cm−2. These results indicate that ZrB2, as a new type of negative electrode catalyst, has a good application prospect in VRFB and opens up a new category of VRFB catalysts.