|Place of Conferral||北京|
|Keyword||功能碳材料 碳纤维 氮掺杂多孔碳 超级电容器 染料吸附|
碳纤维和氮掺杂多孔碳因具有优良的性质而广泛应用于制备纤维增强复合材料、传感、催化、储能、环境修复等领域。传统制备碳材料的原料都是以化石资源为主，但随着化石能源的大量消耗，不仅出现了资源短缺现状，环境还受到了一定程度的破坏。因此，开展以可再生的、廉价的、绿色环保的生物质为原料制备碳材料的方法具有重要的意义。本论文以棉花短绒为原料，开展了以下3个方面的研究工作。1. 以棉花短绒为原料，经提纯，氨基化等步骤制备出易溶于氢氧化钠溶液的纤维素氨基甲酸酯，并以此为纺丝原料，经过溶解、纺丝制备纤维素基纤维。再经过浸渍、预氧化、碳化等工艺制备出碳纤维。主要考察了不同的碳化温度对试样碳化得率以及碳纤维力学性能的影响。结果表明，以磷酸氢二铵为浸渍剂能有效的提高试样的碳化得率。制备的碳纤维表面光滑，断面呈现致密的实芯结构。在未经热拉伸和热处理情况下，900 °C碳化的试样抗拉强度达到了0.72 Gpa，碳化得率为36.4%。2. 以纤维素氨基甲酸酯为原料，尿素为氮源，氢氧化钠为溶剂及活化剂。纤维素氨基甲酸酯经溶解在氢氧化钠/尿素溶液中，干燥成型后进行煅烧制备出氮掺杂多孔碳，该材料孔隙结构可调，具有超高的比表面积，比表面积达到3700 m2/ g。同时，考察了不同的碳化温度对试样得率、元素组成、形貌、孔结构的影响。实验结果表明，通过调节煅烧温度可以控制试样的孔结构和形貌。碳化温度越高，试样的碳得率，氮、氧含量越低；同时，试样的孔隙率大幅增加，比表面积、孔容、孔径也随之增加。碳化的试样为多级孔隙结构，其中在900 °C碳化的试样呈现出三维内交联孔隙结构，比表面积达到3700 m2/ g，孔容为3.60 cm3/g，氮含量达到7.7%，氧含量为7.8%。3. 以制备出的氮掺杂多孔碳为研究对象，对其潜在的应用性能进行了评价，首先，将其制备成超级电容器，考察了其电化学性能。其次，以该材料为吸附剂，考察了它对亚甲基蓝染料的吸附性能。实验结果表明：所制备的氮掺杂多孔碳具有优异的电化学性能和染料吸附性能。在三电极体系中，6 M KOH电解液中具有339 F/g (电流密度为0.5 A/g) 的高的比电容容量，并且在电流密度为20 A/g时比电容容量为246 F/g，表明其具有优异的倍率特性（保留率为初始的73%）。此外，循环5000次后比电容容量仍可保持初始容量的95%。此外，在1 M H2SO4电解液中具有282 F/g（电流密度为0.5 A/g）的比电容容量。在双电极体系中进行测量时，在6 M KOH电解液中具有289 F/g（电流密度为0.5 A/g）的比电容容量，同时具有优异的倍率特性（电流密度为20A/g时电容容量保留率为初始的72%），并且电流密度为2A/g下，经5000此循环后比电容容量能够保持在初始容量的92%。对亚甲基蓝吸附性能实验结显示，所制备的氮掺杂多孔碳对其具有优异的吸附性能，其中900 °C碳化制备的氮掺杂多孔碳对亚甲基蓝的吸附量最大，吸附容量达到1551 mg/g。
Carbon fibers and nitrogen-doped porous carbon are used in a broad variety of applications in composites, sensor, catalysts, energy storage, and environment protection due to their unique property and high performance. Traditional methods for the preparation of carbon based materials are based on fossil fuels, however, with the rapidly consumption of oil and gas, not only the fossil fuels shortage is becoming more obvious, the environmental pollution poses another big challenge. Therefore, it is urgent and practically important to develop a process preparing carbon materials based on renewable, low-cost, and green biomass resources. In this work, carbon based materials were prepared with cotton linter as starting material. The main contents of the work and major conclusions are as follows: 1. The soluble cellulose carbamate (CC) was prepared through purification and amination with cotton linter as raw material. Then the CC based fiber was synthesized after dissolving and spinning processes with CC as starting material. The carbon fiber was fabricated via impregnation, oxidation, and carbonization procedures. The yield and mechanical properties of carbon fibers at different carbonization temperature were investigated. The results showed that the yield of carbon fiber can be effective improved with the diammonium hydrogen phosphate (DAP) as impregnation. The as-prepared carbon fiber had a relatively smooth surface and approximately round compact morphology in cross-section. Without hot-stretching and post-thermal treatments steps, the as-prepared carbon fibers carbonizing at 900 °C reach tensile strength around 0.72 GPa with the carbon yield up to 36.4%.2. Nitrogen-doped porous carbons with tunable pore structures and ultrahigh specific surface area were designed and prepared from sustainable biomass precursor CC via simultaneous carbonization and activation with CC, urea, and NaOH as precursor, nitrogen source, and solvent and activation agent, respectively. The yield, element composites, morphology, and pore structure of samples at different carbonization temperatures were investigated. The results showed that the HNPCs were structure-tunable in terms of pore structure and morphology by adjusting the calcination temperatures. With the increase of the carbonization temperature, the yield, nitrogen, and oxygen content of samples were decreased, while the porosity, specific surface area, pore volume, and pore diameter were increased. The as-synthesized sample carbonizing at 900 °C not only resulted in three-dimensional and interconnected pore structure, but also exhibited ultrahigh specific surface area (3700 m2/g), high pore volume (3.60 cm3/g), and high level of nitrogen-doping (7.7%).3. The performance of supercapacitor and adsorption for organic dye methylene blue (MB) were explored with the nitrogen-doped porous carbon materials as electrode and adsorbent, respectively. The results showed the N-doped porous carbon had excellent electrochemical properties and dye adsorption performance. For the application of supercapacitor, the electrode made of N-doped porous carbon at 900 °C (HNPCs-900) had high specific capacitance of 339 F/g and 282 F/g at the current density of 0.5 A/g in three-electrode system with 6 M KOH and 1M H2SO4 as electrolyte, respectively. Furthermore, the outstanding rate capacity (~73% retention at current density of 20 A/g) and excellent cycle stability (~95% retention after 5000 galvanostatic charge-discharge cycles at current density of 5 A/g) in KOH electrolyte were achieved. In two-electrode system, the electrode made of HNPCs-900 exhibited high specific capacitance of 289 F/g at 0.5 A/g and excellent rate capacity (~72% retention at current density of 20 A/g) as well as good cycling stability (~92% retention at 2 A/g) after 5000 cycles. Furthermore, the HNPCs-900 showed an unprecedented adsorption capacity for organic dye methylene blue (1551 mg/g).
|周鑫. 功能型生物质基碳材料的设计、制备与应用[D]. 北京. 中国科学院大学,2017.|
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