Investigation of advanced catalytic effect of Co3O4 nanosheets modified carbon felts as vanadium flow battery electrodes

Abstract 3D petal-like Co3O4 nanosheets with the mesoporous structure are produced successfully and coated firmly on carbon fibers by simply electrodepositing cobaltous acetate tetrahydrate and its subsequent calcination. The morphology of the precursor, which dominates the structure of the final product, evolves from layers of moss-like amorphous cobalt compounds to Co3O4 nanosheets with obvious lattice defects. Compared with Co3O4 nanoparticles synthesized by the traditional hydrothermal method, the nanosheet layered structure has a higher specific surface area and more active sites. The 3D Co3O4 nanosheets are further used as modification materials to fabricate electrodes with excellent electrocatalytic activity and good reversibility towards both the positive and negative vanadium redox reactions. With the Co3O4 nanosheets modified electrodes, the battery demonstrates remarkably improved performance and shows excellent long-term stability with a dischargeable capacity decay rate of only 2.9 mAh per cycle, which is 70% lower than that of the battery with unmodified electrodes.