Nanoarchitectonics of Hierarchically Porous Carbon Nanospheres via Mild Air Activation for High‐Performance Supercapacitors

ABSTRACT Hydrothermal carbonization of biomass derivatives typically produces nonporous carbon spheres with limited electrochemical activity. This study reports a mild and environmentally friendly activation strategy for forming a hierarchical pore structure in glucose‐derived carbon nanospheres. Using poly (diallyldimethylammonium chloride) (PDDA) as a soft template during hydrothermal polymerization, the as‐prepared carbon nanospheres are subsequently activated in air at controlled temperatures. The optimized sample activated at 800°C (CNSs‐800) exhibited a high specific surface area of 1131.2 m 2 g −1 , well‐developed micro‐, meso‐, and macropores and a balanced defect/ordered carbon structure (I D /I G = 0.98). In a three‐electrode system, CNSs‐800 delivered a specific capacitance of 206 F g −1 at 1 A g −1 . When assembled into a symmetric supercapacitor, it achieved an energy density of 4.78 Wh kg −1 at 1100 W kg −1 and retained 85% of its initial capacitance after 20,000 charge–discharge cycles at 10 A g −1 . Compared with several recently reported carbon‐based supercapacitors, CNSs‐800 shows competitive performance owing to its morphology‐preserving mild air‐activation strategy and hierarchical micro/mesoporous structure. This work provides a scalable and environmentally friendly route to high‐performance porous carbon nanospheres without extensive use of corrosive chemical activators.