Hydrogen‐Treated Rutile TiO 2 Shell in Graphite‐Core Structure as a Negative Electrode for High‐Performance Vanadium Redox Flow Batteries

Hydrogen‐treated TiO 2 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@TiO 2 :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 V 3+ /V 2+ reaction on the surface of reduced TiO 2 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.