Interfacial Charge Transfer Activates Graphene Shells for High‐Efficiency and Durable Vanadium‐Cerium Redox Flow Batteries

ABSTRACT Vanadium‐cerium redox flow batteries (V‐Ce RFBs) have emerged as a promising alternative to all‐vanadium systems, owing to their higher operating voltage and reduced material costs. However, their practical implementation is hindered by the sluggish kinetics of the Ce ³⁺ /Ce ⁴⁺ redox reaction, and previous strategies have often yielded only marginal performance gains or inadequate stability under strongly acidic conditions. Herein, we develop a novel electrocatalyst comprising iron‐cobalt alloy nanoparticles encapsulated with a graphene shell (FeCo@Gr) for the positive electrode of V‐Ce RFBs. The graphene layer not only serves as a corrosion‐resistant barrier but also exhibits high catalytic activity for Ce ³⁺ /Ce ⁴⁺ redox reaction due to electron transfer from electronic coupling with the alloy core. The FeCo@Gr‐modified electrode demonstrates significantly improved catalytic activity for the Ce ³⁺ /Ce ⁴⁺ redox reaction compared to pristine GF. In a single‐cell battery test, it achieves an energy efficiency of 63.4% at 200 mA cm ⁻² and a peak power density of 433 mW cm ⁻² , substantially exceeding the performance of the unmodified electrode. Density functional theory calculations indicate that the electron‐rich graphene layer facilitates charge transfer and lowers the reaction energy barrier. This work provides an effective strategy for developing durable and high‐performance electrocatalysts for flow battery applications.