Vanadium fl ow battery (VFB) is one of the various candidates considered for energy storage systems. To further improve

the performance of VFBs, adding functional groups to the surface of carbon nanotube (CNT) to provide more active sites

for promoting redox reactions of vanadium ions is one desirable way. For the purpose, adenosine (AD) and adenosine

monophosphate (AMP) attached carboxylic acid functionalized CNTs (CACNT) (ADCNT and AMPCNT) are used as the

catalysts. Furthermore, proper co-doping of N, O or N, P, O atoms included in AD and AMP may increase diversity of active

sites. In this regard, ADCNT and AMPCNT are considered better catalysts than CACNT for increasing the reaction rate of

vanadium ions because a large number of hydrophilic groups belonged to ADCNT and AMPCNT can maximize contact

between catalyst and electrolyte. Quantitatively, charge transfer resistance is decreased by ~ 37.6% (ADCNT) and ~ 42.3%

(AMPCNT), while peak reversibility is ~ 5.8% improved with the new catalysts. Regarding performance evaluations, voltage

and energy effi ciencies of VFBs using AMPCNT are best even at 250 mA cm −2 , proving the above benefi ts of AMPCNT

catalyst. Conclusively, this study confi rms that larger functional groups compared to those traditionally used can act as eff ective

catalysts, while multi-atom co-doped catalysts can be used for the performance improvement of VFBs.