Advanced aqueous phenazine redox flow battery enhanced by selective interfacial water behavior on Co/NC modified electrode.

Although aqueous organic redox flow battery (RFBs) is a highly promising energy storage device, the redox reaction kinetics of the anode organic electrolyte material, especially for phenazine derivatives, are limited by low electrochemical activity of traditional porous carbon electrodes. Herein, Co/NC composite electrocatalyst was elaborated to significantly enhance the redox reaction kinetics of phenazine derivatives, in which Co/NC electrocatalyst could improve energy efficiency of aqueous phenazine RFBs by 43.2 % compared to pure carbon felt electrodes at current density of 100 mA/cm. Control experiments combined with density functional theory calculations identified that in addition to the more reactive sites provided by relatively large electrochemical active surface area accelerate the redox reaction of phenazine derivatives, the Co and CoNC reaction sites provided by Co modification not only reduce the energy barrier, but also provide new convenient reaction pathways based on selective interfacial water behavior, further promoting the reduction reaction of phenazine derivatives. This study gives an in-depth understanding of the synergistic effects between phases in composite electrocatalysts and proposes a new behavioral mechanism for the redox reactions of organic electroactive species on the surface of catalytic electrodes.