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

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 °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 °C exhibited peak potential separation (ΔE_p) values as low as ~ 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.