Carbon paper or felt due to its large reactive surface area, chemical stability in highly acidic solution has been widely used as electrode in VRFB, however poor electrochemical activity, low kinetics toward oxidation and reduction of vanadium ions, and less wettability arising from its hydrophobic nature limit its wide-spread application. Several modification techniques have been used to improve the catalytic activity of carbon electrode toward vanadium redox couples mainly including thermal, chemical and electrochemical treatments. Most of the modification techniques result increased activity of carbon electrode attributed to its enhanced available surface area and surface functional groups. In this work carbon paper is etched by using cobalt oxide (Co3O4) as catalyst and is used as electrode for vanadium redox flow battery cell. The etched carbon paper is found better than pristine one in terms of charging overpotential, IR drop, charge/discharge capacities and energy efficiency at all working current densities. Etched carbon paper showed almost 31.0 Ah/L discharge capacity at initial working current density of 50 mA/cm2 compare to 16.0 Ah/L of pristine one, While 16 Ah/L at 150 mA/cm2 where pristine and thermally treated (TT) carbon paper have no performance. Similar effect was noticed in terms of energy efficiency, the etched carbon paper showed 70% energy efficiency at 150 mA/cm2 which is dramatically higher than pristine and thermally treated carbon paper electrodes. The improved performance is attributed to increased surface area, wettability and presence of microscopic pores on the surface of etched carbon paper.