Developing cost-effective and environmental-friend electrode material is critical to accelerate the large-scale commercialization of the all-vanadium redox flow batteries. Herein, we propose and develop a twin-cocoonderived self-standing carbon material by a green and safe preparation method. This facile degumming and carbonization process allows the twin-cocoon-derived monolithic carbon material to be decorated with nitrogen defects and oxygen functional groups. It has been demonstrated that this nitrogen-oxygen-rich monolithic carbon electrode material yields a promoted electrochemical activity for both V2+/V3+ and VO2+/VO2+ couples, causing a 50% decrease in redox potential difference and a 192% increase in diffusion slope as compared with the commercial carbon paper, thereby improving the electrochemical reversibility and enhancing the mass transfer kinetics. It is also found that the flow battery using nitrogen-oxygen-rich monolithic carbon electrode material shows 83% higher average discharge capacity and 20% higher energy efficiency than that with carbon paper at the current density of 100 mA cm(-2), promising a high-performance and low-cost all-vanadium redox flow battery. This work opens a new way to developing monolithic carbon electrode material that possesses great potential applications in flow battery and other electrochemical energy conversion and storage systems.