Gas sorption and supercapacitive properties of hierarchical porous graphitic carbons prepared from the hard-templating of mesoporous ZnO/Zn(OH)₂ composite spheres

Three-dimensional (3D) hierarchical porous carbon materials (PCMs) with graphitic carbon walls are facilely prepared through the hard-templating of acid-labile mesoporous ZnO/Zn(OH)₂ spheres. Furfuryl alcohol or phloroglucinol is employed as a carbon precursor for two hierarchical porous carbon materials (PCM-F and PCM-P). The basic surfaces of ZnO/Zn(OH)₂ are highly suited to the polymerization of the carbon precursors without extra catalysts. After carbonization followed by mild acid etching, hierarchical PCMs are obtained. These PCMs consist of interconnected turbostratic carbon wall structures. Gas sorption analysis indicates the surface areas of PCM-F and PCM-P are 1013 and 1075 m² g^-1, respectively. The corresponding pore volumes are very large, 3.39 and 3.01 cm³ g^-1, respectively. The uptake abilities for carbon dioxide and hydrogen are investigated at 196 and 77 K, respectively. The PCM-P reveals higher uptake of H₂ (1.19 wt%) and CO₂ (282.0 cm³ g^-1) than for PCM-F. In contrast, PCM-F shows a high gravimetric specific capacitance of 329.5 F g^-1 based on galvanostatic charge/discharge curves at a current density of 0.1 A g^-1. The PCM-F exhibits stable capacitance retention after 10,000 cycles at a current density of 5 A g^-1.