Antimony-doped tin oxide as an efficient electrocatalyst toward the VO2+/VO2+ redox couple of the vanadium redox flow battery

Abstract

The low electronic conductivity of metallic oxides limits their electrocatalytic activity toward the VO²⁺/VO₂⁺ redox reaction in a vanadium redox flow battery (VRFB). In this work, antimony-doped tin oxide (ATO) nanoparticles achieve higher electronic conductivity than tin dioxide nanoparticles. In addition, the doped Sb(V) enhances the negative charge on the surface of the SnO₂, which contributes to adsorption of vanadium ions on the ATO surface. As a result, the reversibility of the VO²⁺/VO₂⁺ redox reaction on ATO is much better than that on SnO₂. The energy efficiency of the VRFB with optimized ATO nanoparticle loading on graphite felts is improved to 73.09% in comparison with that with pristine graphite felt (61.00%) or SnO₂ nanoparticle-coated graphite felt (65.47%) at 300 mA cm⁻². Thus, ATO nanoparticle-coated graphite felt is a desirable positive electrode for VRFB applications.