Fast Microwave Synthesis of Hierarchical Porous Carbons from Waste Palm Boosted by Activated Carbons for Supercapacitors.

The synthesis of biomass-derived porous carbons (PCs) for supercapacitors by conventional two-steps method (chemical activation after carbonization) is complicated and time-consuming. In this study, we present a one-step microwave activation strategy to prepare hierarchically PCs from waste palm boosted by activated carbons (ACs). ACs with various specific surface areas (14, 642, and 1344 m²·g-1) were used for the first time to fast absorb microwave energy for converting waste palm into hierarchically PCs, that is, PC1, PC2, and PC3, respectively. The morphological and structural characterizations of PCs were studied. Also, the electrochemical performances of supercapacitors based on PCs as electrodes were further investigated. The results showed that the PC (PC1) boosted by AC with the lowest specific surface area possessed a porous structure (containing micro-, meso-, and macro- pores) with the largest specific surface area (1573 m²·g-1) and the highest micropore volume (0.573 cm³·g-1), as well as the suitable mesoporosity (29.69%). The as-prepared PC1 supercapacitor even in a gel electrolyte (PVA/LiCl) exhibited a high specific capacitance of 226.0 F·g-1 at 0.5 A·g-1 and presented excellent charge-discharge performance with an energy density of 72.3 Wh·kg-1 at a power density of 1.4 kW·kg-1 and 50.0 Wh·kg-1 at 28.8 kW·kg-1. Moreover, this promising method exhibited a simple, rapid, and cost-effective preparation of carbon materials from renewable biomass for energy storage applications.