Carbon-based materials are always used as the electrodes of vanadium redox flow battery (VRFB), but low reaction area and poor electrochemical catalytic activity restrict its application. In the research, to solve these problems, metal-organic framework (MOF)-derived materials are utilized in electrode modification. Firstly, for enhancing the electrochemical catalytic activity and conductivity of MOF, annealing at different temperatures were conducted. Based on the results of cyclic voltammetry tests, the optimizing sintering temperature can be acquired due to the best electrochemical catalytic activity toward vanadium ions. Secondly, the material analysis techniques such as SEM, TEM, XRD, Raman spectroscopy, XPS were used for further realizing the characteristics and the reasons which bring about outstanding performance of catalysts. Finally, the catalyst modified graphite felts were applied in VRFB to test the single cell performance, and the voltage efficiency (VE) and energy efficiency (EE) were significantly improved comparing with the VRFB assembled with pristine graphite felts. In the stability tests, the superior performance also can keep well and without significantly decline in efficiency even after 100 cycles of charge-discharge tests. To sum up, metal-organic framework (MOF)-derived materials developed here provide another effective way to modify the carbonaceous electrodes of VRFB.

Keywords: vanadium redox flow battery; metal-organic frameworks; energy efficiency; electrochemical catalytic activity