One-step activation of high-graphitization N-doped porous biomass carbon as advanced catalyst for vanadium redox flow battery.

In this paper, we reported a one-step activation strategy to prepare highly graphitized N-doped porous carbon materials (KDC-FAC) derived from biomass, and adopted ferric ammonium citrate (FAC) as active agent. At high temperature, FAC was decomposed into Fe- and NH3-based materials, further increasing graphitization degree, introducing N-containing functional groups and forming porous structure. KDC-FAC has superior electrocatalytic activity and stability towards V2+/V3+ and VO2+/VO2+ redox reactions. High graphitization degree can enhance the conductivity of carbon material, and porous structure is conducive to increase reaction area of vanadium redox couples. Moreover, N-containing functional groups are beneficial to improve the electrode wettability and serve as active sites. The single cell tests demonstrate that KDC-FAC modified cell exhibits good adaptability under high current density and superb stability in cycling test. Compared with pristine cell, the energy efficiency of KDC-FAC modified cell is increased by 9% at 150 mA cm-2. This biomass-derived carbon-based material proposed in our work is expected to be an excellent catalyst for vanadium redox flow battery.