Tuesday, 11 October 2022: 17:40
Room 224 (The Hilton Atlanta)
The vanadium redox flow battery (VRFB) has been considered as one of the most promising large-scale energy storage technologies in terms of its long cycle life, high safety and efficiency, and design flexibility. However, the high cost prevents the VRFB technology from broader market penetration. One of the critical components of VRFBs that can significantly influence the effectiveness and final cost is the electrode. Therefore, the development of an ideal electrocatalyst with low cost, large active surface area, good chemical stability, and excellent electrochemical reaction activity toward the VO2+/VO2+ and V2+/V3+ redox reactions is essential for the design of VRFBs. Hence, we synthesized simple, inexpensive, and conductive WOX nanowires (WOXNWs) as the electrocatalysts on the surface of GF via one-step solvothermal process. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) studies revealed that WOXNWs have electrocatalytic effects toward VO2+/VO2+ redox couple at the positive side which enhanced the electrochemical kinetics of the redox reactions. To further improve the electrochemical performance of WOXNWs, the sample was consequently thermally annealed with controlled amount of (H2–Ar) atmosphere to form oxygen vacancy rich hydrogen treated WOXNWs (H-WOXNWs). When used as an electrode in a VRFB single cell, this material showed outstanding performance with an increase in energy efficiency of 9.1% and 12.5% compared to the cell assembled with WOXNWs and pristine GF, respectively at high current density of 80 mA cm−2. The superior performance of the H-W18O49NWs electrocatalyst based electrode is attributed to the presence of a large number of oxygen vacancies which have been shown to act as the active sites for the VO2+/VO2+ redox reaction. Moreover, uniformly immobilized and 1D nature of WOXNWs facilitated charge transport process, enhanced hydrophilicity, and electrolyte accessibility, thus remarkably reduced electrochemical polarization during mass transfer process of active species. The long term cycling performance confirmed the outstanding durability of the as prepared H-WOXNWs based electrode with negligible activity decay after 100 cycles.