Boosting Kinetics of Ce³⁺/Ce⁴⁺ Redox Reaction by Constructing TiC/TiO₂ Heterojunction for Cerium‐Based Flow Batteries

Abstract Cerium, a unique rare earth element, possesses a relatively high abundance, low cost, and high redox voltage, making it an attractive candidate for redox flow batteries. However, the sluggish kinetics and corrosion nature of the Ce³⁺/Ce⁴⁺ electrolyte result in overpotential and degradation of carbon felt (CF) electrodes, which hinders the development of cerium‐based flow batteries. Therefore, it is essential to develop an electrode with high catalytic activity and corrosion resistance to the Ce³⁺/Ce⁴⁺ electrolyte. Herein, a TiC/TiO₂ coated carbon felt (TiC/TiO₂‐CF) electrode is proposed. Remarkably, the TiC/TiO₂ coating effectively minimizes the exposure of the CF to the highly corrosive cerium electrolyte, consequently enhancing the electrode's corrosion resistance. Additionally, X‐ray photoelectron spectroscopy and high‐resolution transmission electron microscopy characterizations reveal the formation of a heterojunction between TiC and TiO₂, which significantly enhances the redox reaction kinetics of the Ce³⁺/Ce⁴⁺ redox couple. Eventually, the practical application of TiC/TiO₂‐CF catalytic electrode in a Ce–Fe flow battery is demonstrated. This study sheds light on the synthesis conditions of the TiC/TiO₂‐CF electrode, elucidates its heterojunction structure, and presents a novel Ce–Fe flow battery system.