Hierarchically porous carbon materials synthesized from sustainable tannic acid with sodium citrate via ice-templating and carbonization for high-performance supercapacitors

Porous carbons are mainly used as electrode materials for commercial supercapacitors because of their large specific surface area, high electrical conductivity, and long-life span. However, highly porous carbons with interconnected multi-modal pore structures are still being pursued to further improve the electrochemical performance. In this study, porous carbon materials (PCMs) with well-interconnected multi-modal pore structures, large specific surface area, and large pore volume were prepared from tannic acid as an eco-friendly and sustainable carbon precursor and sodium citrate as a harmless activation agent via ice-templating and carbonization without an additional activation. The physicochemical characterization of the obtained PCMs revealed that the pore properties and morphology were strongly influenced by the amount of sodium citrate used. The PCMs prepared at a higher amount of sodium citrate showed interconnected hierarchical pore structures with a high specific surface area of 1326.12 m2/g and a total pore volume of 1.19 cm3/g. In a 3-electrode system, the PCM-based electrodes delivered a good supercapacitive performance, including a high specific capacitance of 278 F/g at 1 A/g and a high rate capability of 30% even at 50 A/g. In a 2-electrode system, the symmetric device displayed a high power density of 10.0 kW/kg, a high energy density of 7.05 Wh/kg, and an outstanding charge/discharge cycling stability of 100% after 10,000 cycles. These results suggest that the tannic acid-derived PCMs can be a promising active material for high-performance eco-friendly supercapacitors.