Enhanced energy efficiency of aqueous organic redox flow batteries: carbon-based heterostructure electrodes guided by an interface engineering strategy

Abstract

As an emerging large-scale energy storage technology, aqueous organic redox flow batteries (AORFBs) have drawn widespread focus in the field of energy research. Unfortunately, the inferior electrochemical kinetics of redox reactions on carbon felt (CF) electrodes have limited the power density and energy efficiency of AORFBs, which stands as a major barrier to their practical implementation. In this work, composite electrodes consisting of reduced graphene oxide and carbon felt (rGOCF) with a heterostructure and in situ oxygen doping were fabricated by an interface engineering strategy. The uniform coating and stable integration of rGO sheets and CF in the heterostructure were realized through an interface engineering strategy, which facilitates the formation of a rich network of heterointerfaces to enhance redox reaction kinetics. Compared with the pristine CF electrode system, the TEMPO/Methyl Viologen (TEMPTMA/MV) based AORFB with the rGOCF heterostructure electrode delivered an energy efficiency of 80.05% for 200 cycles at a current density of 50 mA cm⁻². This research offers a novel approach for developing highly active electrodes in AORFBs and improving the energy efficiency of electrochemical systems.