writer：S. Hwang, J. Zhou, T. Tang, K. Goossens, C. W. Bielawski, J. Geng
keywords：SURFACE-AREA, PERFORMANCE, GRAPHENE, ELECTRODES, SHELL, CAPACITANCE, NANOTUBES, GRAPHITE, NETWORKS, OXIDE
source：期刊
specific source：Energy Fuels
Issue time：2021年
Due to their high surface areas and large pore volumes, porous carbons (PCs) are valuable materials for use as electrodes in energy storage and conversion devices. Biomass is an ideal precursor for the preparation of PCs in part because it is sustainable and eco-friendly. Herein, new methodology for converting agarose, a naturally occurring type of biomass that forms robust hydrogels, into PCs with tunable pore structures and high electrochemical performance is described. The synthetic process is straightforward and entails heating a gel that is composed of agarose and potassium oxalate (K₂C₂O₄). Since the salt transforms into gaseous byproducts at elevated temperatures, the decomposition process was harnessed to create activated, open pores as the hydrogel underwent carbonization. For example, a PC with a surface area of 1754.9 m(2) g^-1 and a pore volume of 2.643 cm(3) g^-1 was obtained by heating a mixture of agarose and K₂C₂O₄ in a 1:3 weight ratio at 700 degrees C. The material was subsequently used as the electrode material in a supercapacitor and found to display a specific capacitance of 166.0 F g^-1 at 0.125 A g^-1. Varying the quantity of added K₂C₂O₄ resulted in predictable changes in porosity and thus offered a means to tune the textural properties and the electrochemical performance of the PCs. For example, changing the feed ratio of agarose to K₂C₂O₄ to 1:6 afforded a PC that exhibited a high persistent specific capacitance (64.1 F g^-1 at 5 A g^-1 after 10,000 cycles) and a high-power density (20 kW kg^-1 at 10 A g^-1).