The improvement of organic redox flow battery performance by spherical mesoporous carbon prepared by sol-gel polymerization in water-oil emulsification technique.

Spherical mesoporous carbon (SMC) was prepared by water in oil emulsification combined with sol-gel polymerization and activated with carbon dioxide. The SMCs had an average particle size of 44 μm, a specific surface area of 479 m2 g−1 and with a large mesopore volume of 1.12 cm3 g−1. The slit-shaped mesopores were embedded into the wall surface of the SMCs. As electrocatalysts, the electrochemical properties of SMCs toward the anthraquinone-2-sulfonic acid (AQS) and 1,2-benzoqinone-3,5-disulfonic acid (BQDS) redox couples were examined. The SMCs facilitated the fast reversible-electrochemical reaction with the kinetic rate constant of 9.73 × 10−4 cm s−1 for BQDS, and of 4.39 × 10−3 cm s−1 for AQS. Subsequently, the electrodes of an aqueous organic flow battery were fabricated onto carbon paper and carbon cloth using SMCs as the electrocatalysts. The flow battery performance was improved by around 1.7-fold, when the SMCs had a mass loading of 2 mg cm−2 with 20 wt% Nafion, fabricated onto carbon cloth. However, there was no significant performance improvement when the SMCs were fabricated onto carbon paper. Moreover, SMCs provided the most outstanding power density over other carbon electrocatalysts (i.e., graphene, Vulcan XC-72 and Vulcan XC-72R), from 2 to 3 fold, according to the superior physical and electrochemical properties. • SMCs prepared via sol-gel polymerization with water-oil emulsification system. • SMCs had superior electrochemical properties over carbon glass up to 100 times. • SMCs greatly improved an aqueous organic flow battery performance. • Power density from SMCs was about 2–3 time better over other carbon electrocatalysts. [ABSTRACT FROM AUTHOR]