Facile preparation of an oxygen-functionalized carbon felt electrode to improve VO²⁺/VO₂⁺ redox chemistry in vanadium redox flow batteries

Herein, a new method for the facile introduction of oxygen-containing functional groups on a carbon felt electrode in a short treatment time has been proposed for application in a vanadium redox flow batteries (VRFBs). Benzoyl peroxide (BPO) can produce free radicals by attacking the C[dbnd]C bonds or C[sbnd]H bonds of the carbon felt. The generated unstable free radicals allow further reactions with oxygen to yield oxygen-containing functional groups on the surface of the carbon felt electrode. The electrochemical performance of the BPO-treated carbon felt electrode toward the VO²⁺/VO₂⁺ redox reaction was superior to that of the pristine carbon felt electrode. Therefore, the VRFB cell employing the BPO-treated carbon felt electrode showed an outstanding energy efficiency of 75% at a current density of 100 mA cm⁻². This improvement is attributed to the well-known electrocatalytic effects of the oxygen-functionalized surface properties of the BPO-treated carbon felt electrode.