Nano-catalytic layer engraved carbon felt via copper oxide etching for vanadium redox flow batteries

Electrode architecture design is vitally important for achieving high-power and long-life vanadium redox flow batteries. This work starts with a rationale for the polarization losses of current flow battery electrodes on a basis of the well-developed design of a proton exchange membrane fuel cell. With a gained understanding from the electrode design of a fuel cell, an attempt is made to engineer the architecture of carbon felt by creating a nano-catalytic layer on carbon fiber surfaces via a facile and powerful copper oxide etching method. By engraving nano-holes on fiber surfaces, the carbon felt can deliver attributes of expanded reaction surface area, abundant defective sites and excellent structural stability under swift-flowing electrolyte without sacrificing mass transport properties. With the nanoholed and defective carbon felt, the battery demonstrates a remarkably improved performance with 85.1% energy efficiency at 320 mA cm(-2), 21.8% larger than that of the pristine carbon felt. In addition, the flow battery with this new electrode shows excellent long-term stability up to 2000 cycles. It is envisioned that such an electrode design strategy would inspire the future development of advanced fibrous electrodes for flow cell applications. (C) 2019 Elsevier Ltd. All rights reserved.