Controlled synthesis of graphite oxide: Formation process, oxidation kinetics, and optimized conditions
Controlled synthesis of graphite oxide: Formation process, oxidation kinetics, and optimized conditions
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DOI：
10.1016/j.ces.2017.10.028
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发表时间：
2018-02-02
影响因子：
4.7
通讯作者：
Bao, Ningzhong
中科院分区：
文献类型：
--
作者：
Li, Chang;Shi, Yexun;Bao, Ningzhong
氧化石墨（GO）是研究最广泛的材料之一，由于其独特的性能，已被测试用于许多应用。然而，石墨氧化的复杂转移和反应速率的定量描述仍然不可用，这实质上阻碍了高质量GO和其他石墨烯相关材料的大规模生产。本文采用改进的Hummers法从鳞片石墨（FG）中制备GO。在整个氧化过程中，监测时间依赖性互补结构域（即起始GO结构域和剩余FG结构域）的尺寸和颜色演变。FG在酸性氧化介质中的氧化过程可以解释为受相界控制的收缩区过程。采用R2数学模型，系统地研究了反应温度、硫酸浓度、氧化剂对氧化反应的影响，得到了反应速率常数（k）和动力学参数（Ea，lnA）。使用动力学结果，氧化过程和从FG到GO的转化率因此变得可控。利用XRD、TGA和XPS研究了中间产物和最终GO产物，以揭示氧化机理。FG的氧化程度和产品表面主要官能团的含量因此可以被优化。研究结果对于理解石墨氧化的基本机理，实现氧化程度可控、含氧官能团比例可调的高质量GO的工业化生产具有重要意义。(C)2017爱思唯尔有限公司版权所有
Graphite oxide (GO) is one of the most extensively studied materials and has been tested for numerous applications due to its unique properties. Nevertheless, a quantitative description of complicated transfer and reaction rates of the oxidation of graphite is still not available, which essentially hinders large-scale production of high-quality GO and other graphene related materials. In this work, GO is prepared from flake graphite (FG) by a modified Hummers method. Size and color evolutions of time-dependent complementary domains, i.e. the starting GO domain and the remaining FG domain, are monitored during the entire oxidation process. The oxidation of FG in acidic oxidizing medium can be interpreted as a contracting area process controlled by phase boundary. Reaction rate constant (k) and kinetic parameters (Ea, lnA) are obtained after a systematic investigation of the influence of reaction temperature, concentration of sulfuric acid, and oxidizing agent on the oxidation, with the aid of R2 mathematical model. Using the kinetic results, the oxidation process and the conversion rate from FG to GO thus become controllable. Both intermediate products and final GO products are studied using XRD, TGA, and XPS to reveal the oxidation mechanism. The degree of oxidation of FG and the content of major functional groups on the surface of products can thus be optimized. Our research results are valuable to understanding fundamental mechanism of graphite oxidation and to achieving industrial production of high-quality GO with controllable degree of oxidation and tunable proportion of oxygen-containing functional groups for a variety of applications. (C) 2017 Elsevier Ltd. All rights reserved.