Silk Protein-Derived carbon fabric as an electrode with high Electro-Catalytic activity for All-Vanadium redox flow batteries

Abstract

In this study, we fabricated silk protein-derived carbon fabrics (SCFs) as electrodes for vanadium redox flow batteries (VRFBs) using a commercial silk fabric through a facile pyrolysis process, without any post-treatment. After the pyrolysis, the intrinsic fabric morphologies of the SCFs were maintained, resulting in highly macroporous structures. In addition, even after pyrolysis at high temperature above 1,600 degrees C, the SCFs contain sufficient heteroatoms such as oxygen and nitrogen on their surface, originated from their protein nature. As a result, SCF electrodes prepared by heating at 1,600 degrees C exhibited peak potential separation (Delta E-p) values as low as similar to 164.5 and 164.6 mV at a scan rate of 5 mV s(-1) in both catholyte and anolyte, respectively, demonstrating excellent electro-catalytic activity. Furthermore, single cell-based VRFBs using symmetric SCF-1600//SCF-1600 pairs revealed a considerably high energy efficiency of 86.8%, which is 10.3% higher than that of VRFB using commercial carbon felt electrodes (76.5%). After 100th galvanostatic charge/discharge cycles, the capacity retention of 91% that was achieved, verified the long-term cycling stability. Our study suggest that the suitable heteroatom contents and carbon microstructures of electrode material can enhance the electrochemical performances, resulting in high electro-catalytic activity for vanadium redox flow batteries.