添加剂辅助水热热解制备尺寸可控纳米孔碳微球

以KCl和HCl为添加剂,以果糖和淀粉为前躯体,通过水热处理和后续热解制备碳微球,探讨添加剂的作用机制。结果表明:碳微球具有纳米孔隙结构和表面含氧官能团。在2种前躯体中,添加剂均能促使具有规则球形的微球尺寸呈不同幅度的增大,平均直径控制在0.53～6.67μm之间。碳微球的形状和尺寸源于水热处理,而热解促使微球的结构由聚合物向玻璃碳转变,同时伴随着超过20%的尺寸收缩和近50%的质量损失。在水热反应过程中,氯化氢主要促进前期的多糖水解动力学以及单糖脱水与分裂动力学,而氯化钾主要加速后期微球的生长动力学。微球的生长涉及2种主要模式:构造单元交联生长和微粒合并生长。

Additive-assisted hydrothermal route to synthesize nanoporous carbon microspheres with controlled particle size

Carbon microspheres were synthesized by the hydrothermal treatment of saccharides (fructose and starch) in the presence of additives (HCl and KCl) and the subsequent pyrolysis, and the role of the additives in the hydrothermal reaction was also investigated. The results show that carbon microspheres with well-developed nanoporous structures and surface oxygen functional groups are obtained. Both of the additives in the saccharide solutions induce the enlargement of the size of the microspheres. The mean diameter of the microspheres can be tailored in a range from 0.53μm to 6.67 μm. The morphology of the microspheres depends on the reaction kinetics during hydrothermal treatment. During pyrolysis, the microstructure of the microspheres is transformed from polymer to glassy carbon, which is accompanied by a mass loss of about 50% and a contraction of over20% in scale. Both of the additives display distinct effects on the stages of the hydrothermal reaction of the saccharide solutions. The HCl mainly accelerates the hydrolysis kinetic of polysaccharide and the dehydration and fragmentation of monosaccharide, while the KCl chiefly enhances the growth kinetic of the microspheres. The growth of the microspheres is performed through two main ways: the reactive oxygen functionalities present in both the surfaces of the microspheres and the building units and the merged fine microspheres.