Porous Carbons with Tunable Mesoporous Structure Induced by Coupled Chemical Activation for High‐Performance Zinc Ion Hybrid Capacitors

Pore structure is the foundation for the capacitive performance of porous carbons. Micropores are pivotal spaces for storing hydrated Zn²⁺ ions. Elucidating the charge storage mechanism of micropores is essential to develop porous carbon cathodes for zinc ion hybrid capacitors (ZIHCs). Herein, a coupling strategy of NaOCN and Na₂CO₃ activation is developed to regulate the pore structures of porous carbon nanosheets (PCNs). NaOCN, in situ formed by cyanide groups reacting with partial Na₂CO₃, couples with Na₂CO₃ activation to construct 0.6-1 nm and 1-2 nm micropores. Excessive NaOCN activation causes the collapse of 0.6-1 nm micropores and formation of 2-4 nm mesopores by the generated NaCN template. 0.6-1 nm micropores serve to store Zn²⁺ ions. 1-2 nm micropores and 2-4 nm mesopores are responsible for rapidly transporting Zn²⁺ ions. Benefiting from the highest 0.6-1 nm micropore ratios (23.8%) and 1-2 nm micropore ratios (30.0%) that facilitate robust Zn²⁺ ion storage and fast kinetics, the optimized PCNs (PCN-0.5) deliver superior specific capacitance, remarkable rate capability and excellent durability. The assembled PCN-0.5//Zn ZIHCs exhibit a high energy density of 121 Wh kg^-1 at 80 W kg^-1 and 44 Wh kg^-1 even at 40435 W kg^-1.