Highly Electrocatalytic Activity of Micro and Nanocomposite Phase Engineering of MoO3−x@K3PW12O40 Decorated on Graphite Felt for High-Performance VRFB

Abstract

The catalytic activity of metal cations exchanged with heteropoly acids (HPA) and the selectivity towards precursor composite materials can be tailored by adjusting the reaction mechanism. A structural defect engineering strategy was developed for the metallic phase of O-MoS₂, doped with a Keggin-type HPA to serve as a double gyroid layer (O-MoS₂@HPA). This was achieved through thermal oxidation treatment to enable a high surface area by depositing abundant catalytically active sites on the graphite felt. Optimization strategies involving MoO_3−x (MoO_3−x@K₃PW₁₂O₄₀) species have been crafted, anchoring active sites in a spherical nanomorphology through the self-assembly of acid. This development introduces a new approach for enhancing electrocatalysts, aiming for superior performance in VRFB. The electrochemical results show remarkable enhancement in electrocatalytic behavior with abundant heteroatom active sites, promoting oxidation at a high current density of 150 mA/cm², achieving an outstanding 84.62% high energy efficiency. This result is 14% higher than pristine graphite felt and exhibits extraordinary stability after 1350 cycles, overcoming the sluggish kinetic mechanism that limits redox active materials. This study creates new avenues for the design of hybrid micro/nanostructured materials on cathodes and anodes to achieve excellent performance as electrocatalysts for VRFB.