Mn3O4 Nanoparticle-Decorated Carbon Cloths with Superior Catalytic Activity for the VII/VIII Redox Reaction in Vanadium Redox Flow Batteries

Mn3O4 nanoparticle-decorated carbon cloths are prepared as the electrodes for vanadium redox flow batteries. The Mn3O4 nanoparticles are prepared using a two-step process, in which MnOOH nanoflakes are electrodeposited on the surface of the carbon cloth and subsequently converted to Mn3O4 nanoparticles by a thermal treatment. The prepared electrode exhibits a superior electrocatalytic activity toward the VII/VIII redox reaction. It is demonstrated that the peak potential separation of the VII/VIII redox reaction on the as-prepared electrode is reduced from 402.0 mV to 82.4 mV at a scan rate of 5 mV s−1 when the pristine carbon cloth is deposited with Mn3O4 nanoparticles. The flow battery with carbon cloths decorated with 0.31 mg cm−2 of Mn3O4 nanoparticles as the electrode exhibits an energy efficiency of 88 %, which is 17 % higher than that of the battery assembled with the pristine carbon cloth at a current density of 100 mA cm−2. Therefore, the superior electrocatalytic activity of Mn3O4 nanoparticles reported offers a promising approach to improve the performance of carbon-based electrodes, which can reduce the capital cost of vanadium redox flow batteries. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim