Microwave‐Induced Two‐Phase Activation of Phytic Acid‐Derived Carbon for High‐Power Vanadium Flow Battery Electrodes

ABSTRACT The two‐phase KOH‐assisted microwave activation of phytic acid‐derived graphitic carbon effectively addresses the persistent trade‐off between hydrophilicity and conductivity in graphite‐felt electrodes for vanadium redox flow batteries. In the initial phase, rapid defect generation and phosphate removal enhance oxygen functionalities, while prolonged activation promotes re‐graphitization with abundant surface hydroxyl groups, resulting in the optimized catalyst PC‐KM‐5. This catalyst demonstrates a 9.29‐fold increase in electrical conductivity compared to the precursor carbon, while maintaining a strong affinity for aqueous vanadium electrolytes. It transforms a highly hydrophobic felt (contact angle 141.2° ± 2.69°) into a fully wettable electrode with immediate electrolyte absorption. When applied to graphite felt, PC‐KM‐5 improves the peak current density of the VO 2+ /VO 2 + couple to 151.4 mA cm − 2 and reduces the charge‐transfer resistance from 9.30 to 1.52 Ω, surpassing both pristine felt and PC‐decorated felt. In single‐cell, PC‐KM‐5 electrode sustains operation at 500 mA cm − 2 , achieving an energy efficiency of 62.9% and a discharge capacity of 24.1 Ah L − 1 at 400 mA cm − 2 , which is 2.62 times greater than that of conventional electrode. The energy efficiency remains at 99.3% of its initial value after 1000 cycles, underscoring the structural robustness and practical viability of PC‐KM‐5 for high‐power, long‐life flow batteries.