One-step electrochemical synthesis of synergistic N/S co-doped hierarchically porous graphite felt for high-performance VRFBs

Rational electrode design unlocks the kinetic limitations of vanadium redox flow battery (VRFB). Herein, we present a one-step electrochemical oxidation strategy under mild acidic conditions to fabricate N-S co-doped graphite felt (GF@N-S) electrodes. This innovative approach achieves simultaneous in situ sulfonation and amination on carbon surface, constructing a hierarchical porous architecture with dual-active sites—a previously unreported configuration for VRFBs. Distinguished by its simplicity, scalability, and metal-free, our method circumvents cost limitations while suppressing hydrogen evolution side reactions. The GF@N-S electrode exhibits a remarkable triple synergy: (1) N-S co-doping significantly reduces charge-transfer resistance, (2) an optimized pore architecture enhances mass transport, and (3) a tailored electronic structure dramatically accelerates reaction kinetics. As a result, the electrode achieves remarkable energy efficiency of 85.8 % at 300 mA cm⁻² and 75.0 % at 500 mA cm⁻², outperforming even state-of-the-art metal/carbon-nanomaterial hybrids. Notably, it exhibits exceptional stability with negligible active-site degradation over 1000 cycles. This work establishes a transformative paradigm for non-metal electrode engineering, seamlessly integrating atomic-scale doping control with industrial-scale manufacturability, and propelling the development of sustainable, high-performance energy storage systems.