Synthesis and Characterization of Electrospun Nickel-Carbon Nanofibers as Electrodes for Vanadium Redox Flow Battery

Electrodes based on electrospun nickel carbon nanofibers (Ni/CNF) are investigated as highly active both for anodic and cathodic reaction. Scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM) analyses show metal nanoparticles embedded in graphitic carbon nanofibers. A high surface area due to large mesoporous structure formation is calculated for the Ni/CNF by BET analysis. Cyclic voltammetry (CV) results indicate the higher electrocatalytic activity toward the [VO] 2+ /[VO 2 ] + as well as V 2+ /V 3+ redox reactions for Ni/CNF with respect to the bare CNF. Charge-discharge tests show energy efficiency (EE) value of 68%, voltage efficiency (VE) of 72% and a coulomb efficiency (CE) of 94% for Ni/CNF at 160 mA·cm −2 . The electrochemical performance recorded at high current density could be ascribed to the high electrical conductivity as well as the polarity on the carbon surface due to the nickel nanoparticles. In particular, an increment in terms of wettability improves the accessibility to the aliphatic and carboxyl groups on the composite surface sample enhancing the reversibility at the electrode/electrolyte interface.