Two-Step Preparation of Hierarchical Porous Carbon Materials Derived from Tannin for Use as an Electrode Material for Supercapacitors

Abstract

The development and utilization of biomass and agroforestry processing byproducts for high-value applications have been an important topic in the field of renewable materials research. Based on this, a two-step microwave hydrothermal pre-carbonization and KOH activation method was proposed to synthesize tannin-based activated carbons with a high specific surface area, hierarchical pore structure, and good electrochemical performance. The microstructure, texture properties, and physicochemical characteristics were investigated. The results show that the prepared tannin-based activated carbons presented a hierarchical pore structure (micro- and mesopores) with a specific surface area as high as 997.46 m3 g−1. The electrochemical analysis shows that the tannin-based activated carbons have good wettability and charge transfer rates. Under the three-electrode system with 6 M KOH as the electrolyte, the active material TAC600-4 had a maximum specific capacitance of 171 F g−1 at 0.5 A g−1. As the current density increases to 10 A g−1, the specific capacitance can still be maintained at 149 F g−1, indicating a good rate capability. Therefore, the specific surface area and pore size of tannin-based activated carbons can be effectively adjusted by the alkali/carbon ratio, making it a promising supercapacitor electrode material and providing a new method for the high-value development of tannins in the field of electrochemical energy storage.