Fungi-Derived, Functionalized, and Wettability-Improved Porous Carbon Materials: An Excellent Electrocatalyst toward VO2+/VO2+Redox Reaction for Vanadium Redox Flow Battery

Porous carbon derived from fungi (FDC-K) was prepared by two-step treatments including hydrothermal treatment followed by high-temperature pyrolysis with KOH, and served as electrocatalyst toward VO2+/VO2+ redox reaction for vanadium redox flow battery (VRFB). The as-prepared FDC-K is mainly microporous with large BET surface area up 1412.7 m2 g−1. Moreover, FDC-K is functionalized by oxygen-containing groups from KOH treatment. Water contact angle measurement confirms the outstanding wettability of FDC-K. These three characteristics are beneficial for the electrode process of VO2+/VO2+ reaction. In comparison with direct-carbonization carbon and two-step carbon without KOH activation, FDC-K shows superior electrocatalytic properties. VO2+/VO2+ couple exhibits improved electrochemical activity and reversibility on FDC-K. The charge-discharge performance of the cell using FDC-K as positive catalyst shows that using FDC-K can increase the utilization rate of active species and capacity retention. After 50 cycles at 50 mA cm−2, the capacity retention for FDC-K can keep 78.1%, 15.4% larger than that for the pristine one. Moreover, the corresponding energy efficiency increases by 5.8% after using FDC-K. Our study reveals that fungi-derived porous carbon is an excellent electrocatalyst for VO2+/VO2+ reaction, showing the promising prospect in VRFB.