Engineering Palladium-Nickel Alloy Sites on N-Doped Reduced Graphene Oxide for Enhanced Catalytic Hydrogenation of Vanadium Electrolytes

• The PdNi/NrGO catalyst enables rapid, clean reduction of V4+ to V3.5+. • UV-Vis spectroscopy confirms the high-purity generation of V3.5+. • The electrolyte shows low resistance and robust electron conductivity. • Bimetallic design lowers catalyst cost by ∼29% vs commercial Pd/C. • VRFB achieves 76.7% energy efficiency over 100 cycles at 100 mA cm-2. High-performance, low-cost electrolyte production remains a significant challenge for the commercialization of all-vanadium redox flow batteries (VRFBs). Herein, we demonstrate a robust strategy to engineer palladium-nickel (PdNi) alloy active sites on nitrogen-doped reduced graphene oxide (NrGO) for the efficient catalytic hydrogenation of VO 2+ (V 4+ ) to the V 3.5+ . The resulting PdNi/NrGO catalyst outperforms commercial Pd/C, driven by synergistic Pd-Ni electronic interactions and the structural advantages of the N-doped support, which prevent particle agglomeration and enhance charge transfer. Kinetic analysis reveals a remarkable turnover frequency (TOF) of 0.765 s -1 , enabling rapid and impurity-free electrolyte generation. Crucially, the synthesized V 3.5+ electrolyte delivers superior VRFB performance, achieving average efficiency gains of 16.6% (Coulombic efficiency), 11.0% (Energy efficiency), and 11.0% (Voltage efficiency) relative to the commercial baseline, while maintaining stable operation over 100 charge-discharge cycles. Furthermore, this bimetallic approach reduces catalyst costs by approximately 45% relative to commercial Pd/C and up to 71% compared to high-loading Pt-based systems, offering a scalable and economically attractive solution to the electrolyte imbalance issue in next-generation grid storage systems..