A flexible electrospun carbon nanofiber (CNF)-based electrode decorated with Mn₃O₄ is prepared starting from a solution containing polyacrilonitrile (PAN) mixed with manganese acetate (Mn(OAc)₂). A thermal treatment at 270°C in air and a subsequent at 900°C in inert gas allow to obtain a flexible electrospun carbon nanofibers decorated with spinel manganese oxide (denoted as Mn₃O₄/CNF) characterized by suitable performance for vanadium redox flow battery (VRFB) application. Pristine electrospun carbon nanofibers CNF were prepared by using a similar method to compare the electrochemical data with respect to the decorated CNF. A homogeneous distribution of the metal oxides on the carbon nanofibers is showed by scanning electron microscopy (SEM) analysis. Cyclic voltammetry (CV) curves show a higher electrocatalytic activity toward the [VO]²⁺/[VO₂]⁺ as well as the V²⁺/V³⁺ redox reactions with respect to the pristine electrospun CNF electrode, both in terms of peak to peak separation, DE_[VO]²⁺_/[VO2]⁺ = 0,15 V vs. 0,28 V, and I_pa/I_pc[VO]²⁺_/[VO2]⁺ ratio, 1,48 vs 1,58, respectively. The improved performance is attributed to the hydrophilicity enhancement due to the oxygen groups availability that favour the surface mechanism process on the carbon nanofibers decorated with metal oxide nanoparticles.