Preparation And Electrochemical Performance Of Lignin-derived Mesoporous Carbon And Its Composites

Porous carbons have many advantageous properties with respect to their utility in electrochemical energy field, which requires constrained space such as electrode material of supercapacitor or solid-state hydrogen storage. The attractive properties of porous carbons include their abundance, chemical and thermal stability, feasible processability and so on. Mesoporous carbons(MPCs), which have been explored more than other carbon classes, have been traditionally used as catalyst supports or adsorbents, but lately they are increasingly empolyed or finding potential applications in the fabrication of aforementioned materials.Lignin is a kind of important support materials in plants, who keep xylem hard to bearing the weight of the whole plant. Because of lignin’s high reserves next to cellulose in the world, it is a sort of environmentally benign and renewable natural resource. This article presents the preparation and characterization of liginin-devived MPCs, emphasizing on the use of low-cost and facilitate carbon precursor and tethering porous morphology. And in consideration of its hierarchical porosity, the lignin-derived MPC can be the matrix material of supercapacitor that improves an excellent electron conduction and rate performance. The main contents of this dissertation are summarized below:(1) Mesoporous carbons(MPCs). MPCs were synthesized by using the liginsulfonate, obtained from the pollution of paper industry, as carbon sources, glutaraldehyde/paraformaldehyde as cross-linking agents and polyvinylpyrrolidone(PVP) as a dispersing agent. The precursors for MPCs, appeared bister solids, were synthesized by hydrothermal and solvothermal methods. KOH or ZnCl2 were used as pore-enlarging agents. After that, the crude products were calcinated and charred in a horizontal tube furnace. The as-synthesized MPCs have high specific surface areas, large pore volumes and narrow pore size distributions and almost porewalls of the MPCs have been graphitized, which endorse MPCs as leading candidates in application of electrochemical materials. Additionally, the fabricated capaciters showed a high specific capacitance in a constant current charge and discharge test and displayed a good retention for more than 1000 cycles in a cycling test. Furthermore, because of the mesoporous structure that will not limit the ion motion within the pores, the activated carbon showed a good rate capability.(2) MPCs /NiO composites. The MPCs/NiO composites were synthesized via the sol-gel process using Ni(NO3)2·6H2O as a nickel source and the MPCs as matrix. In order to load the Ni+ on the MPCs, the mixture were refluxed in alkaline conditions. The MPCs/NiO composites were finally synthesized by drying in vacuum and calcining in a horizontal tube furnace. Specific surface area and pore volume of the MPCs/NiO composites all decreased due to NiO’s filling of the carbon pore. The fabricated battery showed a dood specific capacitance in a constant current charge and discharge test and displayed a nice retention for more than 1000 cycles in a cycling test. NiO’s pseudocapacitance and MPCs’ s good structure make the MPCs/NiO composites good electrochemical properties.