3D cross-linked structure of dual-active site CoMoO4 nanosheets@graphite felt electrode for vanadium redox flow battery.

Abstract

Transition metal oxides (TMOs) can accelerate the sluggish kinetics of vanadium redox reaction, but face challenges like limited active sites and difficulties in nanometerization, highlighting the urgent need for new TMO electrocatalysts for vanadium redox flow battery (VRFB). CoMoO₄ features high electrochemical activity, numerous redox sites, flexible control, and short electron pathways. Herein, a high catalytic and super stable graphite felt electrode modified in situ with network cross-linking CoMoO₄ nanosheets (CoMoO₄@GF) was prepared via hydrothermal and heat treatment method to enhance VRFB performance. CoMoO₄@GF have large specific surface area, super hydrophilicity, and abundant reaction places, possessing well mass transfer, low charge transfer resistance, and sufficient catalytic sites. Therefore, the composite electrodes exhibit great electrocatalytic activity towards VO²⁺/VO₂⁺ and V³⁺/V²⁺ redox reactions and excellent stability for VRFB. At 200 mA cm^-2, the energy efficiency (EE) of the CoMoO₄@GF modified VRFB improved by 19.14 % over the blank VRFB with pristine graphite felt, and remained cycle stable after 350 cycles at 150 mA cm^-2. This work not only enriches the types of TMOs catalysts in VRFB, but also opens up a new direction for the research of bimetallic TMOs.