Synergistic Effect of Carbon Nanofiber/Nanotube Composite Catalyst on Carbon Felt Electrode for High-Performance All-Vanadium Redox Flow Battery ParkMinjoon JungYang-jae KimJungyun LeeHo il ChoJeaphil 2016 Carbon nanofiber/nanotube (CNF/CNT) composite catalysts grown on carbon felt (CF), prepared from a simple way involving the thermal decomposition of acetylene gas over Ni catalysts, are studied as electrode materials in a vanadium redox flow battery. The electrode with the composite catalyst prepared at 700 °C (denoted as CNF/CNT-700) demonstrates the best electrocatalytic properties toward the V<sup>2+</sup>/V<sup>3+</sup> and VO<sup>2+</sup>/VO<sub>2</sub><sup>+</sup> redox couples among the samples prepared at 500, 600, 700, and 800 °C. Moreover, this composite electrode in the full cell exhibits substantially improved discharge capacity and energy efficiency by ∼64% and by ∼25% at 40 mA·cm<sup>–2</sup> and 100 mA·cm<sup>–2</sup>, respectively, compared to untreated CF electrode. This outstanding performance is due to the enhanced surface defect sites of exposed edge plane in CNF and a fast electron transfer rate of in-plane side wall of the CNT.