Tuesday, 31 May 2022: 17:20
West Meeting Room 213 (Vancouver Convention Center)
As one of the most promising electrochemical energy storage systems, vanadium redox flow batteries (VRFBs) have received increasing attention owing to their attractive features for large-scale storage applications. However, their high production cost and relatively low energy efficiency still limit their feasibility. 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, high electrical conductivity, 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 have synthesized a novel catalyst based on the MoO2–reduced graphene oxide (rGO) composite (MoO2–rGO) was synthesized through a simple hydrothermal approach followed by annealing process. The as-prepared MoO2–rGO nanocomposite as the electrode material for all-vanadium redox flow batteries (VRFBs) show that the MoO2 nanoparticles are uniformly decorated within the rGO nanosheets and exhibits not only excellent electrocatalytic redox reversibility toward V3+/V2+ and VO2+/VO2+ but also larger anodic and cathodic peak currents than the other individual MoO2 and rGO samples. Such an improvement can be attributed to the uniform distribution of MoO2 nanoparticles on the surface of rGO could avoids restacking of the rGO sheets and suppresses the agglomeration of the nanoparticles, which might increase the effective surface area and hence improve the mass transport at the electrode–electrolyte interface. Furthermore, the presence of oxygen vacancies on MoO2, the high electrical conductivity of rGO, and the high content of oxygen functional groups play the roles of the active sites toward to vanadium ion redox reaction. Using the prepared electrodes, the columbic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) of the VRFB at 80 mA cm−2 are 95.01%, 82.14%, and 78.05%, respectively, which are much higher than that of the cell assembled with pristine graphite felt electrodes. The difference becomes even more significant at high current densities.