Coal tar phenols based hierarchical porous carbon nanospheres for high performance supercapacitor anodes

Hierarchical porous carbon nanospheres (HPCNs) with uniform morphology are highly significant for the application of supercapacitors. In this paper, carbon nanospheres (CNs) are synthesized via St & ouml;ber method with small molecular phenols fractionated from low-medium temperature coal tar. The factors behind the morphology of CNs have been investigated during the synthesizing process. It is found that the CNs prepared with a phenol content of 50 wt% and a hydrothermal temperature of 160 degrees C display the characteristics of an average particle size of 667 nm and a uniform morphology with narrow particle size distribution. Besides, the processing time of CO2-activation are then optimized based on the pore structure and electrochemical properties of CNs. The optimized CNs offer the features of ultra large specific surface area (2812 m(2) g(-1)), hierarchical porous structure and numerous nitrogen and oxygen functional groups. The as-prepared electrode is thus featured by a high specific capacitance of 258 F g(-1) at 0.5 A g(-1), good rate characteristic and remarkable electrochemical stability (only 0.7% loss after 8000 cycles). The present strategy provides a promising candidate for the high-value utilization of coal tar and the low-cost preparation of electrode materials.