Carbon nanotubes (CNTs) are promising electrocatalysts for vanadium redox fl ow batteries (VRFBs); however, their 

inherent hydrophobicity poses challenges for practical application. In this study, we introduce a straightforward and industrially

feasible urea-assisted treatment that facilitates carbonyl-rich oxygen functionalization on CNT surfaces through 

mild oxidation, while maintaining the integrity of the graphitic framework. X-ray photoelectron spectroscopy confi rms a 

signifi cant enrichment of carbonyl (C = O) species, resulting in a marked enhancement in surface wettability, with only 

a moderate reduction in electrical conductivity. Electrochemical analyses demonstrate a substantial increase in catalytic 

activity towards both VO 2+ /VO 2+ and V 2+ /V 3+ redox couples, with anodic peak current densities approximately 2.32 times 

greater than those of pristine CNTs and a decreased charge-transfer resistance (66.1% post-treatment). When applied to 

graphite felt electrodes, CNT/urea exhibits improved single-cell VRFB performance, achieving an energy effi ciency of 

approximately 64.5% and a discharge capacity of 25.77 Ah L⁻¹ at 400 mA cm⁻², along with stable operation over 1,000 

cycles. This research highlights urea-assisted carbonyl functionalization as a cost-eff ective and scalable approach for 

developing hydrophilic, catalytically active CNT electrodes for practical VRFB applications.