Abstract:

Lignin based porous carbon have been widely studied as the electrode materials for supercapacitors device owing to its low-cost, renewable and simple preparation process. In this paper, lignin nanoparticles (LNP) isolated from wheat straw biomass was used as the carbon precursor, pretreated by activation with ZnCO₃, and then prepared to LNP based hierarchical porous carbon (LPC) through slow pyrolysis at different temperatures (600—800℃). Furthermore, in-situ growth of δ-MnO₂ was loaded onto the surfaces of LPC by the lights of solution reaction method. The resultant MnO₂/LPC nanocomposite with three-dimensional (3D) nano-lamellar structure was successfully synthesized. The micromorphology, chemical composition, and electrochemical performances of MnO₂/LPC were characterized by means of SEM, XRD, FTIR and electrochemical tests. The study results suggested that the behaviors of MnO₂in-situ growing on LPC were significantly affected by the pyrolysis temperature of LPC preparation. As the pyrolysis temperature of LPC increased from 600℃ to 800℃, the pattern of δ-MnO₂ nanocrystals evolved from the clustered particles to 3D cross-linked porous lamellar nanostructure. In addition, the as-prepared MnO₂/LPC electrode had shown excellent electrochemical performances. The specific capacitance of MnO₂/LPC at 800℃ could reach 145F/g at 1A/g, yet maintained 110F/g as the current density increasing to 5A/g, indicating that it had also a better rate performance (75.9%). Meanwhile, the symmetric supercapacitor assembled from this composite material had a high specific capacitance of 87F/g and energy density of 3.03W·h/kg in the two electrode system.

Key words: lignin nanoparticles, porous carbon, manganese dioxide(MnO₂), electrochemical

摘要：

由于生物质具有来源广泛、成本低廉、可再生等优点，近年来生物质基多孔炭作为电极材料在超级电容器方面的应用被广泛研究。本文以麦草生物质分离得到的纳米木质素（lignin nanoparticles, LNP）为炭前体，经碳酸锌活化预处理后在不同热解温度（600~800℃）下制备LNP基分级多孔炭（LPC）。并通过溶液反应法将δ-MnO₂纳米晶原位负载于LPC上，成功合成具有三维（3D）纳米片状结构的炭基复合材料（MnO₂/LPC）。借助扫描电子显微镜、X射线衍射仪和傅里叶变换红外光谱仪等手段耦合电化学性能测试技术，对MnO₂/LPC的微观形貌、结构组成及电化学性能等进行表征。研究结果显示，LNP衍生LPC的热解温度对δ-MnO₂原位生长行为有着重要影响。当LPC的热解温度从600℃升高到800℃时，原位生长的MnO₂从纳米簇状颗粒逐渐演变成3D交联的多孔纳米片层结构。此外，以MnO₂/LPC制备的工作电极表现出优异的电化学性能。当电流密度为1A/g时，在800℃下的MnO₂/LPC具有最高的质量比电容（145F/g）；当电流密度增大至5A/g时，其比电容量仍保持为110F/g，并具有良好的倍率性能（75.9%）；同时，该复合材料组装成的对称超级电容器在二电极体系下具有较高的比电容（87F/g）和能量密度（3.03W·h/kg）。

关键词: 纳米木质素, 多孔炭, 二氧化锰, 电化学