Porous Carbons with Tunable Mesoporous Structure Induced by Coupled Chemical Activation for High-Performance Zinc Ion...

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.