Probing the Thermal Deoxygenation of Graphene Oxide Using High-Resolution In Situ X-ray-Based Spectroscopies
Probing the Thermal Deoxygenation of Graphene Oxide Using High-Resolution In Situ X-ray-Based Spectroscopies
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DOI：
10.1021/jp203741y
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发表时间：
2011-09-01
影响因子：
3.7
通讯作者：
Hamilton, Jeremy
中科院分区：
文献类型：
--
作者：
Ganguly, Abhijit;Sharma, Surbhi;Hamilton, Jeremy
尽管氧化石墨烯作为石墨烯主体前体的重要性得到了很大的发展，但其详细的电子结构及其在热还原过程中的演化在很大程度上仍不清楚，阻碍了其潜在的应用。我们发现，高分辨率的原位X射线光电子能谱和X射线吸收光谱的结合为监测氧化石墨烯薄膜的脱氧过程和综合评价氧化石墨烯薄膜在热还原过程不同阶段的电子结构提供了有力的手段。结果表明，边平面上的羧基是高度不稳定的，而羰基则更难去除。结果一致地支持在中等热活化度(类似于400℃)下，通过基面环氧化物与相邻羟基反应形成苯酚基团。苯酚基团占优势，在1000℃的温度下仍能存活，首次观察到600℃费米能级附近的态密度(DOS)急剧增加，这表明在热还原的氧化石墨烯中芳香结构逐渐恢复。
Despite the recent developments in graphene oxide due to its importance as a host precursor of graphene, the detailed electronic structure and its evolution during the thermal reduction remain largely unknown, hindering its potential applications. We show that a combination of high-resolution in situ X-ray photoemission and X-ray absorption spectroscopies offer a powerful approach to monitor the deoxygenation process and comprehensively evaluate the electronic structure of graphene oxide thin films at different stages of the thermal reduction process. It is established that the edge plane carboxyl groups are highly unstable, whereas carbonyl groups are more difficult to remove. The results consistently support the formation of phenol groups through reaction of basal plane epoxide groups with adjacent hydroxyl groups at moderate degrees of thermal activation (similar to 400 degrees C). The phenol groups are predominant over carbonyl groups and survive even at a temperature of 1000 degrees C. For the first time, a drastic increase in the density of states (DOS) near the Fermi level at 600 degrees C is observed, suggesting a progressive restoration of aromatic structure in the thermally reduced graphene oxide.