Graphite felt etching Co ₃ O ₄ as a cathode to improve electrochemical characteristics for vanadium redox flow batteries

Abstract In this study, a simple method involving immersion and heat treatment was used to modify graphite felt, enabling the attachment of Co 3 O 4 and altering its morphology. The etching process created nanorod structures, which significantly increased the surface area and improved wettability. A Co(NO 3 ) 2 concentration of 4 m m demonstrated optimal electrochemical activity compared to pristine graphite felt. Following the modification, the electrochemically active surface area reached a high value of 131.71 cm 2 , the charge transfer resistance decreased to 12.27 Ω, and the exchange current density increased to 25.02 mA/cm 2 . Cyclic voltammetry measurements revealed that GF4 exhibited reversible redox activity across various scan rates and maintained stability over 50 cycles at a scan rate of 1.0 mV/s, with I pa / I pc = 1.18 and ∆ E p = 220 mV. These findings indicate that the modification method improves the performance of graphite felt cathodes in vanadium redox flow batteries, emphasizing its potential for energy storage.