Dual Molten Salt Synthesis of Oxygen Rich Hierarchical Porous Carbon as Cathode Materials for Zinc‐Ion Hybrid Capacitor

Abstract Hierarchical porous carbon exhibits great potential as the cathode materials for zinc ion hybrid capacitor. Herein, a convenient and novel strategy is reported to prepare oxygen rich hierarchical porous carbon derived from alginate by dual molten salt strategy using KHCO ₃ and NaHCO ₃ as activators. The obtained oxygen rich hierarchical porous carbon (OPC‐700) possesses a well‐developed interconnected porous skeleton, large specific surface area (1193.6 m ² g ⁻¹ ), and abundant oxygen functional groups. Owing to the co‐effect, the prepared electrode shows a specific capacity of 410.7 F g ⁻¹ and superior electrochemical stabilization. More importantly, the Zn// ZnSO ₄ //OPC‐700 hybrid capacitor assembled with OPC‐700 as the cathode, zinc foil as the anode delivers an energy density of 124.5 Wh kg ⁻¹ and superior electrochemical stabilization in 2 m ZnSO ₄ .