Preparation of High-Performance Hierarchical Porous Activated Carbon via a Multistep Physical Activation Method for Supercapacitors

Biomass-derived activated carbons (ACs) are regarded as important electrode materials for supercapacitors (SCs) due to their abundance and large specific surface areas (SSAs). Here, we develop a multistep physical activation strategy by combining water vapor and CO₂ activation to prepare apricot shell-derived activated carbons (ASACs). Compared to the traditional single physical activation method, such a multistep activation strategy is conducive to forming an excellent hierarchical porous structure. The as-obtained AC_VC-4 displays a high SSA and pore volume, and its effective pore volume and the mesoporous volume fraction are 0.720 cm³ g^–1 and 55.76%, respectively. Furthermore, the AC_VC-4 has a superior specific capacitance of 39.17 F g^–1 at 0.5 A g^–1 as the electrode material in the 1-ethyl-3-methylimidazolium tetrafluoroborate electrolyte for SCs. When the current density increases from 0.5 to 10 A g^–1, its capacitance retention rate reaches 87.77%, which is far higher than that of other ASACs and commercial YP-50F. We believe that the multistep activation strategy for preparing ACs could open a new way to obtain high-performance electrode materials for SCs.