Template-activated bifunctional soluble salt ZnCl2 assisted synthesis of coal-based hierarchical porous carbon for high-performance supercapacitors.

A series of coal-based hierarchical porous carbons with adjustable pores were successfully prepared with the assistance of the soluble salt Zinc chloride (ZnCl 2). During the carbonization process, ZnCl 2 , with a low melting point (238 °C), "in situ occupied" and "occupied" within the coal solids to generate interconnected pores, which acted as a template. Simultaneously, the activation of ZnCl 2 reduced the oxygen content of products and further improves their electrical conductivity. Optimization of the mass of the salt and the carbonization temperature resulted in targeted product with a suitable specific surface area (1581 m2 g−1) and unique pores (V meso /V total = 45%), which exhibited a high specific capacitance (470.7 F g−1 at 0.5 A g−1) in 6 M KOH electrolyte. The symmetrical supercapacitor of targeted product has favorable rate performance (256.7 F g−1 at 0.5 A g−1, 84.8% capacity retention at 30 A g−1) and excellent cycling performance (after 10000 cycles, the specific capacitance increases to 115% of the initial capacity at 10 A g−1). In the EMIMBF 4 electrolyte system, the energy density is 95.31 Wh kg−1 at 213.13 W kg−1. Therefore, this work provides an effective method to improve the green and efficient use of coal. [Display omitted] • The salt template method is used to synthesize the coal-based hierarchical porous carbons(CPCs) for the first time. •ZnCl 2 plays a dual function of template - activation in the carbonization process. •The materials obtained an interconnected hierarchical porous structure derived from the melting properties of ZnCl 2. •The material exhibits high specific capacitance (470.7 F g−1 at 0.5 A g−1) and excellent cycling performance. [ABSTRACT FROM AUTHOR]