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

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.