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掺氮、还原石墨烯量子点的一步温和制备及其环境催化应用研究
王珏华
学位类型硕士
导师张懿 ; 赵赫  
2017-07
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业环境工程
关键词还原石墨烯量子点 掺氮 无金属芬顿 一步制备 环境催化
摘要

以氧化石墨烯(GO)为原料,通过一步还原制备得到掺氮、还原性的石墨烯量子点(Nitrogen-doped reduced graphene oxide quantum dots, N-rGQDs),其具有良好的荧光性能、化学稳定性及生物兼容性,目前已被广泛应用于生物成像、光催化、能量转换等领域。然而,N-rGQDs的制备通常采用较复杂、高能耗的两步法,且N-rGQDs表面结构可控性差。因此,本文提出了一种温和、一步制备N-rGQDs的绿色制备方法,且在制备过程中同时实现尺寸、结构可控;制备得到的量子点具有良好的环境催化应用前景,本文对其在环境催化领域的催化性能和机理进行了探讨和分析,取得了以下创新性成果:1)在常温常压下,利用无金属芬顿切割制得N-rGQDs,N-rGQDs切割制备过程进行的跟踪、分析和监控结果显示,发现氧化石墨烯量子点的氧化损伤有一定修复,其含有的C-O键和C=O键降低了 21%,并成功实现了对芳环氮(Nar)、叔胺氮[Ar-N-(CH3)2]以及氨基氮(C-NH2)三种主要含氮结构的有效控制。因N-rGQDs具有优异的催化性能,本文将其应用在了臭氧催化体系,并通过计算化学手段对催化机理进行了分析探讨,得出N-rGQDs的三种N结构中Nar为主要活性位点,Ar-N-(CH3)2为辅助活性位点,为定向调控和制备高效催化剂提供了思路。2)设计、制备并最终获得了一种光催化活性较强的多孔C3N4/N-rGQDs复合光催化剂,并考察了N-rGQDs结构、负载量对催化性能的影响。复合光催化剂的光催化性能对照组提升1.8倍,从不同N-rGQDs结构、N-rGQDs负载量等角度探讨了催化机理,发现N-rGQDs中的Nar结构最有利于促进催化活性,通过优化条件,N-rGQDs的最佳负载量为gN-rGQDs/g多孔C3N4 = 3.4×10-5。3)选取最优结构的N-rGQDs及负载条件,制备得到N-rGQDs与不同结构C3N4复合的光催化材料,并主要从材料物理形貌特点和化学键改变情况两个角度考察不同C3N4结构对光催化性能的影响。发现C3N4的物理结构对复合催化剂的催化活性有较大的影响,选取体相 C3N4/ N-rGQD5、多孔 C3N4/ N-rGQD5以及纳米片层 C3N4/ N-rGQD5三种材料作为催化剂时,目标污染物的去除率依次为53.8%,98.0%和99.0%,同时这三种材料的反应速率常数依次为 3.49×10-3 mg/(L.min)、1.80×10-2 mg/(L.min)以及2.27×10-2 mg/(L.min)。由此可见,具有多孔和纳米片层结构的复合材料催化活性较高,这是由于具有多孔和纳米片层结构的C3N4基底比表面积较大,有利于促进材料的复合效率。此外,伴随着C3N4结构的改变,对复合材料化学键结构的影响不明显,进一步说明C3N4的物理结构对催化剂的反应活性有重要影响。

其他摘要

Graphene quantum dots (GQDs) are monodisperse graphite particles below 10 nm in diameter. With strong fluorescence, chemical inertness, biocompatibility and low toxicity, GQDs exhibit promising applications in bioimaging, photocatalysis, energy conversion, optoelectronics and sensing. One of the greatest challenges for GQDs fabrication originates from the strong chemical inertness and stability of GO; hence, the synthetic methods are generally complex, high energy consumption and operated under severe conditions. Moreover, the surfaces of GQDs obtained via mentioned methods are prone to involve oxygenous functional groups. However, GODs with low degree of oxidative erosion, the reduced GQDs (rGQDs), tend to exhibit high catalytic activities and higher quantum yields. Hence, we obtained N-rGQDs in one-step under room temperature and pressure using H2O2 and HA as metal-free Fenton regents. The one-step cutting, reduction and N-doping process for N-rGQDs fabrication was explored via manipulating the proportion of regents. Furthermore, N-rGQDs were applied in the environmental catalytic degradation systems. Innovative and promising results had been obtained as follows:1) N-rGQDs were obtained via the metal-free Fenton method. It was feasible to produce size controlled and structure controlled N-rGQDs through adjusting the proportion of metal-free Fenton agents. N-rGQDs manifested promising application in environmental catalysis, thus it were used as catalyst in oxidation system. During GO cutting process, 21% of C-O and C=O groups decline. Simultaneously, N atoms were incorporated into inter conjugated structure or cutting edges of N-rGQDs. With the proportion of HA increasing, the content of aromatic N (Nar) and tertiary amines N [Ar-N-(CH3)2] increased then decreased. With the theoretical study based on DFT, the mechanism was explored, Nar probably played key roles during the reaction, Ar-N-(CH3)2 also made contribution to the reaction. It was feasible to fabricated catalyst with high activities.2) Porous C3N4/N-rGQDs was fabricated, which manifested relatively high catalytic activity compared with bulk C3N4/N-rGQDs. The removal rate constants of pollutants increased 1.6-1.8 times. With the aim to design catalysts with high catalytic activities, the mechanism was explored in each system. The optimum ratio was gN-rGQDs/g多孔C3N4 = 3.4×10-5.3) With the aim to further figure out the correlation between the catalytic activity and the structure of C3N4 in composite catalyst, bulk C3N4/N-rGQDs, porous C3N4/N-rGQDs and nanosheet C3N4/N-rGQDs were fabricated. The result indicated that the structure of C3N4 had great effect on catalytic activity, while the structure of the chemical bond had little effect on catalytic activity. The catalyst with porous structure or nanosheet structure tended to manifested high catalytic activity, which was probably due to the large surface area and exposed active sites.

语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/24216
专题研究所(批量导入)
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王珏华. 掺氮、还原石墨烯量子点的一步温和制备及其环境催化应用研究[D]. 北京. 中国科学院研究生院,2017.
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