Facile preparation of hierarchical porous carbons for supercapacitors by direct carbonization of potassium humate

A simple, cost-effective, and environmentally friendly strategy for the preparation of porous carbons for supercapacitors via direct carbonization of potassium humate is presented. The porous carbons obtained from leonardite potassium humate (denoted as LPC) and biotechnology potassium humate (denoted as BPC) showed macro-meso-micro hierarchical porous structure, moderate surface area (668 m2 g−1 for LPC and 604 m2 g−1 for BPC) and were enriched in oxygen-containing functional groups on the surface. These porous carbons applied as electrode materials for supercapacitors exhibited an excellent capacitive behavior in basic, acid, and neutral aqueous electrolytes. The respective specific capacitances for LPC and BPC were 223 and 200 F g−1 at current density of 50 mA g−1, and 175 and 151 F g−1 at current density of 2.5 A g−1 in a 3 M KOH electrolyte. Moreover, the porous carbons had high area specific capacitance (up to 33.4 μF cm−2), superior cycling performance, and low resistance. This work demonstrates a promising preparation route for large-scale production of hierarchical porous carbons for high-performance supercapacitors.