Mechanochemical Synthesis of N-Doped Graphite Nanoparticles: A Promising Material for Flow Vanadium Battery Applications

This study addresses the critical need for advancements in power density and energy efficiency for the widespread adoption of vanadium redox flow batteries (VRFBs). We introduce a novel, productive, and environmentally friendly direct mechanochemical method to synthesize nitrogen-doped graphite nanoparticles (GrNs) as efficient electrocatalysts for vanadium ion redox reactions (VO2+/VO2+ and V2+/V3+). Through low-temperature mechanochemical delamination of graphite in an ammonia atmosphere, we achieve GrNs with a highly defective structure. The duration of the mechanochemical treatment can significantly impact the nature of the catalytically active centers and, hence, the electrocatalytic performance of the obtained materials. Our findings demonstrate that GrN6, prepared with a 6 h treatment, exhibits remarkable efficiency in the VRFB. The GrN6-based VRFB, operating at a current density of 250 mA cm–2, showcases an impressive energy efficiency of 77% for over 500 cycles, coupled with a peak power density of ∼530 mW cm–2, exceeding the performance of VRFBs with conventional graphite felt electrodes (whose energy efficiency does not exceed 70% at 150 mA cm–2). This innovative approach not only provides efficient electrocatalysts for VRFBs but also aligns with environmentally friendly principles, offering promising prospects for a greener energy landscape.