Application of porous biomass carbon materials in vanadium redox flow battery.

Porous nano biomass carbon was synthesized by one-step method using scaphium scaphigerum as carbon source and was employed as negative catalyst for vanadium redox flow battery. Potassium ferrate was used to realize synchronous etching, introducing oxygen-containing groups and graphitization of scaphium scaphigerum to obtain porous, oxygen-rich, high-graphization carbon materials (SS-K/Fe). Compared with traditional two-step method, one-step method has advantages of low-time requirement, high efficiency and no pollution. The prepared SS-K/Fe sample has abundant microporous structure, high degree of graphitization and many oxygen-containing groups. The electrochemical test results show that the prepared carbon-based materials exhibit superior electrocatalytic capability for V2+/V3+ redox reaction. The electrode process can be accelerated from three steps including ion diffusion, electrochemical reaction and electron transfer processes, which are due to the enhancement of wetting performance and electrical conductivity, and an increase of effective catalytic area. Compared with pristine cell, the SS-K/Fe modified cell can improve the energy efficiency by 6.2% at the current density of 50 mA cm-2. This method is expected to realize low cost, green and renewable porous carbon materials for future energy storage systems.