Activated carbon from sugarcane bagasse as a potential positive electrode catalyst for vanadium redox flow battery

•High surface area carbon (1255 m2 g−1) derived from a bio-waste, sugarcane bagasse.•Electrochemically active surface area of the carbon is measured.•Suitability of this carbon is demonstrated in stack level vanadium flow battery. Thermally activated graphite felt (T-GF) electrode coated with carbon derived from the sugar cane bagasse (AC-SCB) was investigated for catalyzing the VO2+/VO2+ reaction in vanadium redox flow battery (VRFB). Micrographs from the scanning electron microscopy and transmission electron microscopy clearly show the highly porous structure of the carbon. The electrochemical surface area of AC-SCB based electrode is nearly 80 times higher than that of the thermally activated graphite felt (T-GF). But the rate constants calculated from cyclic voltammetry study clearly reveals the higher electrocatalytic activity toward the VO2+/VO2+ redox reaction of T-GF in comparison to that of AC-SCB. The charge-discharge study shows energy efficiency of ∼72%, a voltage efficiency of ∼77% and a coulombic efficiency of ∼94% for AC-SCB positive electrode based VRFB at 100 mA cm−2 at the end of 50 cycles. The specific capacity of VRFB at the end of 50 cycles for T-GF/AC-SCB and T-GF are 32 and 25 Ah L−1, respectively.