The template method is often used to synthesize porous materials. However, removing the template during post-processing is difficult and harsh reagents are frequently used, which is unfavorable for the carbon structure. In this paper, a facile and green synthesis route is developed for the synthesis of a 3D honeycomb-like hierarchical porous carbon based on rapid thermal decomposition of the mixture of a low-cost carbon precursor (typically starch) and Na₂CO₃ followed by KOH activation, in which Na₂CO₃ particles are employed as the water-soluble renewable macroporous template. Benefiting from the high specific surface area (1171 m² g⁻¹) and the interconnected micro-, meso-, and macropores, the porous carbon exhibits superior capacitive performance, including high specific capacitance, good rate capability and excellent cycling stability. Moreover, the porous carbon-based symmetric supercapacitor delivers a maximum energy density of 33 W h kg⁻¹ at 100 W kg⁻¹ and presents excellent long-term cycling stability. Considering the easy-availability of the raw materials and the facile synthesis process, this environmentally friendly and cost-effective method can be expected to be widely applied, and we estimate that the obtained porous carbon could find additional applications in other fields.

A simple one-step hydrothermal method is developed for the synthesis of flower-like Co(OH) ₂ microspheres/graphene composites, which exhibit an excellent electrochemical performance.