Hydrogen‐Treated Rutile TiO₂ Shell in Graphite‐Core Structure as a Negative Electrode for High‐Performance Vanadium Redox Flow Batteries

Abstract

Hydrogen-treated TiO₂ as an electrocatalyst has shown to boost the capacity of high-performance all-vanadium redox flow batteries (VRFBs) as a simple and eco-friendly strategy. The graphite felt-based GF@TiO₂ :H electrode is able to inhibit the hydrogen evolution reaction (HER), which is a critical barrier for operating at high rate for long-term cycling in VRFBs. Significant improvements in charge/discharge and electron-transfer processes for the V³⁺ /V²⁺ reaction on the surface of reduced TiO₂ were achieved as a consequence of the formation of oxygen functional groups and oxygen vacancies in the lattice structure. Key performance indicators of VRFB have been improved, such as high capability rates and electrolyte-utilization ratios (82 % at 200 mA cm^-2 ). Additionally, high coulombic efficiencies (ca. 100 % up to the 96th cycle, afterwards >97 %) were obtained, demonstrating the feasibility of achieving long-term stability.