Metal chloride-assisted synthesis of hierarchical porous carbons for high-rate-performance supercapacitor

Abstract

Hierarchical porous carbons with high surface area were prepared by direct carbonization of the polymers which were synthesized via a typical sol–gel method, using terephthalaldehyde and resorcinol as carbon precursors, and metal chloride as reaction assistant. All the metal chlorides could efficiently help to form 3-D porous network carbon with inter-linking irregular particles, and also successfully contribute to the developing of meso-macropores through the packing of grains. Such hierarchical porosity plays an important role for rapid ion diffusion, resulting in an excellent rate capability and low diffusion resistance. Moreover, it should be noted that ZnCl₂ could also act as an in situ activation agent during the carbonization process to generate large surface area of 1106 m² g⁻¹ and pore volume of 1.2 cm³ g⁻¹. In 3 mol L⁻¹ H₂SO₄, high specific capacitance of 174.6 F g⁻¹ by using the ZnCl₂-assisted hierarchical porous carbon as electrode material is obtained and it could retain ca. 84% when the current density increases from 0.1 A g⁻¹ to 20 A g⁻¹. This superior rate capability is higher than that of many hierarchical porous carbons reported in previous literatures. The facile production and excellent electrochemical performance suggested a low cost and effective method to prepare hierarchical porous carbon for energy storage.