Electrospun Carbon Nanofibers Decorated with Mn3O4 for Vanadium Redox Flow Battery

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 Ipa/Ipc[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.