Mesoporous Carbon Integrated with NH₄VO₃ and KI Dual Redox-Active Electrolyte for High-Energy Pseudocapacitive Storage

The rational integration of electrode nanoarchitecture with redox-active electrolyte engineering represents a powerful strategy for overcoming the intrinsic energy limitations of conventional carbon-based supercapacitors. Herein, we report a high-energy symmetric pseudocapacitive system enabled by coupling mesoporous carbon (surface area: 1300 m² g⁻¹; average pore diameter: 5 nm) with a dual redox-active electrolyte consisting of NH₄VO₃ and KI in 1 M Na₂SO₄. The well-defined mesoporous framework ensures rapid ion diffusion and efficient accessibility of electroactive sites, while the reversible V⁵⁺/V⁴⁺ and I⁻/I₃⁻ redox couples introduce substantial faradaic charge storage. Trasatti analysis reveals that 91% of the total capacitance originates from faradaic processes, confirming the dominant contribution of redox mediation. The symmetric device delivers a high specific energy of 33.2 Wh kg⁻¹ at a specific power of 792 W kg⁻¹, corresponding to nearly a fourfold enhancement compared with the conventional Na₂SO₄ electrolyte system. Moreover, the device exhibits excellent rate capability across 1–10 A g⁻¹ and retains 82% of its initial capacitance after 4000 charge–discharge cycles at 4 A g⁻¹, demonstrating robust electrochemical stability. This work highlights the synergistic interplay between hierarchical ion transport within mesoporous carbon and dual redox-mediated charge storage, offering an effective co-engineering strategy for next-generation high-energy pseudocapacitive systems • Mesoporous carbon (1300 m² g⁻¹, 5 nm pores) facilitates rapid ion transport and efficient redox mediation. • A high specific capacitance of 392 F g⁻¹ was achieved in the optimized dual-redox system. • Dual redox-active electrolyte (NH₄VO₃/KI in 1 M Na₂SO₄) enables dominant faradaic charge storage (91% contribution). • The symmetric device delivers 33.2 Wh kg⁻¹, nearly fourfold higher than the conventional electrolyte. • 82% capacitance retention after 4000 cycles at 4 A g⁻¹ confirms long-term electrochemical stability.