In this paper, biomass-derived carbon-based nanosheet from a kind of domestic waste (fish scales) has been successfully prepared as catalysts with high electrocatalytic activity for V2+/V3+ couple of vanadium redox flow battery (VRFB) using hydrothermal, lyophilization, and carbonization treatments. KOH is employed as template and activator, which results in nanosheet structure, ultrahigh porosity, and introduction of oxygen-containing groups. The obtained catalyst (FSC-K) exhibits the advantages of large surface area, many active sites and excellent wettability. FSC-K can effectively reduce electrochemical polarization of electrode reaction and accelerate mass transfer of active species. The cell using FSC-K demonstrates a high energy storage efficiency. Compared with pristine cell, the discharge capacity of FSC-K modified cell is 67.2 mA h at 150 mA cm(-2), increased by 18 mA h, and the corresponding energy efficiency reaches 63.8%, enhanced by 7.9%. The capacity retention of FSC-K modified cell keeps 83.1% after 50 cycles at 75 mA cm(-2), 16.7% larger than that for pristine cell. This work reveals that the electrocatalyst for V2+/V3+ couple obtained from biomass is significant for improving the comprehensive energy storage performance of VRFB. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.