Owing to their scalability, flexible operation, and long cycle life, vanadium redox flow batteries (VRFBs) have gained immense attention over the past few years. However, the VRFBs suffer from significant polarization, which decreases their cell efficiency. The activation polarization occurring during vanadium redox reactions greatly affects the overall performance of VRFBs. Therefore, it is imperative to develop electrodes with numerous catalytic sites and a long cycle life. In this study, we synthesized heteroatom-rich carbon-based freestanding papers (H-CFPs) by a facile dispersion and filtration process. The H-CFPs exhibited high specific surface area (~820 m2 g–1) along with a number of redox-active heteroatoms (such as oxygen and nitrogen) and showed high catalytic activity for vanadium redox reactions. The H-CFP electrodes showed excellent electrochemical performance. They showed low anodic and cathodic peak potential separation (ΔEp) values of ~120 mV (positive electrolyte) and ~124 mV (negative electrolyte) in cyclic voltammetry conducted at a scan rate of 5 mV s–1. Hence, the H-CFP-based VRFBs showed significantly reduced polarization.

Abstract
 1. Introduction
 2. Experimental
  2.1. Preparation of H-CFPs
  2.2. Characterization
  2.3. Electrochemical characterization
 3. Results and Discussion
 4. Conclusions
 References

• Min Eui Lee(Department of Polymer Science and Engineering, Inha University)
• Hyo Won Kwak(Department of Polymer Science and Engineering, Inha University)
• Hyoung-Joon Jin(Department of Polymer Science and Engineering, Inha University) Corresponding Author