Electrocatalytic activity of nitrogen-doped CNT graphite felt hybrid for all-vanadium redox flow batteries

Novel nitrogen-doped CNT-containing graphite felt (N-CNT/GF) hybrid electrodes with high electrocatalytic activity were developed for all-vanadium redox flow batteries (VRFBs). A simple, effective preparation method for N-CNT/GFs using metal (Fe, Co, and Ni) phthalocyanines as the carbon and nitrogen precursor is presented. We found that different metal precursors generated different densities of N-CNTs on the surface of the GFs due to the various interactions of the metals (Fe, Co, Ni) with the carbon precursor during carbonization. Higher density and longer N-CNTs were obtained for N-CNT/GF (Fe), which gave rise to a higher N-doping concentration, enhanced wettability and conductivity, and improved electrochemical reactivity. When used as an electrode in a VRFB single cell, this material showed outstanding performance with an increase in energy efficiency of more than 20% compared to pure GF at a high current density (150 mA/cm2).