Soluble salt self-assembly-assisted synthesis of three-dimensional hierarchical porous carbon networks for supercapacitors

Abstract

Three-dimensional (3D) hierarchical porous carbons (indicated with 3D HPCs) were synthesized via a simple one-pot method using the self-assembly of various water-soluble NaX salts (X: Cl⁻, CO₃²⁻, SiO₃²⁻) as structure-directing templates. By controlling crystallization and assembly of multi-scale salts via a freeze-drying process, 3D porous carbon networks with tailored pore size distribution have been generated by calcining the salts/glucose self-assembly followed by removing the 3D self-assembly of NaX salts via simple water washing. When their applications were evaluated for supercapacitor electrodes as an example, the as-constructed 3D HPCs with large surface area, high electron conductivity, facile electrolyte penetration and robust structure exhibited excellent capacitive performance, namely, high specific capacitance (320 F g⁻¹ at 0.5 A g⁻¹), outstanding high rate capacitance retention (126 F g⁻¹ at 200 A g⁻¹), and superior specific capacitance retention ability (nearly no discharge capacity decay between 1000 and 10 000 continuous charge–discharge cycles at a high current density of 5 A g⁻¹). Based on our soluble salt self-assembly-assisted synthesis concept, it was revealed that salts in seawater are also very suitable for low-cost and scalable synthesis of 3D HPCs with good capacitive performance, which pave the way for advanced utilization of seawater.