Abstract
Improving the electrochemical activity of electrodes is essential to the development of vanadium redox flow battery (VRFB). In this work, we prepared a novel electrode with the modification of nitrogen-doped carboxyl multiwalled carbon nanotubes using dopamine as an eco-friendly nitrogen source (carboxyl MWCNT@PDAt). Characterization and electrochemical measurements reveal that the synthesized carboxyl MWCNT@PDAt-modified graphite felt electrode (carboxyl MWCNT@PDAt/GF) exhibits excellent electrochemical performance toward VO2+/ VO+2VO2+<math><mtext>V</mtext> <msubsup><mtext>O</mtext> <mn>2</mn> <mo>+</mo></msubsup> </math> reaction. Superior battery performance was obtained with the energy efficiency of 80.54% at a current density of 80 mA cm-2. Excellent durability of the carboxyl MWCNT@PDAt/GF electrode was confirmed by long-term charge/discharge tests. The enhanced reaction kinetics of VO2+/ VO+2VO2+<math><mtext>V</mtext> <msubsup><mtext>O</mtext> <mn>2</mn> <mo>+</mo></msubsup> </math> is ascribed to the synergetic effect of oxygen and nitrogen containing groups on graphite felt surface and the presence of nitrogen-doped carboxyl multiwalled carbon nanotubes (MWCNT). The facile approach proposed in this paper provides a new route to the fabrication of electrode with excellent performance for VRFB.