<p>Vanadium redox flow batteries (VRFBs) are a critical technology for large-scale energy storage, and their electrode properties directly determine catalytic activity and structural stability. In this study, copper clusters anchored on MXene sheets (MXene/Cu) are designed as a novel electrocatalyst for the V³⁺/V²⁺ redox reaction. The catalytic performance was systematically evaluated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). For battery performance tests, single cells were assembled using plasma-treated graphite felt coated with the MXene/Cu composite as the negative electrode (MXene/Cu/GF). The results demonstrate that MXene/Cu significantly enhances the catalytic activity of the electrode. At a current density of 200&#xa0;mA&#xa0;cm⁻², the cell employing MXene/Cu/GF as the negative electrode exhibits a 22.53% improvement in energy efficiency compared to plasma-treated graphite felt. Remarkably, after 200 charge–discharge cycles, the composite demonstrates exceptional stability, exhibiting only 5.20% total capacity decay. This superior performance is attributed to the synergistic interaction between Cu clusters and MXene, which introduces abundant active sites on the graphite felt electrode and accelerates the reaction kinetics of the V³⁺/V²⁺ redox couple, thereby enhancing overall cell performance. This work confirms that integrating atomic-level catalysts with two-dimensional MXene offers an effective strategy for advancing VRFB technology.</p>