Real-Time, in Situ Monitoring of the Oxidation of Graphite: Lessons Learned

Morimoto, Naoki; Suzuki, Hideyuki; Takeuchi, Yasuo; Kawaguchi, Shogo; Kunisu, Masahiro; Bielawski, Christopher W.; Nishina, Yuta

doi:10.1021/acs.chemmater.6b04807

Cited by 79 publications

(63 citation statements)

References 44 publications

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“…It requires strong oxidation agents and concentrated acids for a prior intercalation of graphite and a consecutive surface functionalization of the graphene layers, which are confined in graphite starting material . However, under these harsh reaction conditions, over‐oxidation is very likely leading to the rupture of the graphene lattice via formation of CO 2 ,. The loss of carbon atoms from the lattice represents an in‐plane lattice defect that cannot be repaired and must therefore be considered as permanent .…”

Section: Synthesis Of Graphene Oxidementioning

confidence: 99%

Defects in Graphene Oxide as Structural Motifs

2018

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Graphene oxide possesses defects of various kinds. The structure of graphene oxide is reviewed with focus on defects in the σ‐framework of the hexagonal lattice. We clearly distinguish between on‐plane functionalization defects and in‐plane lattice defects. Moreover, vacancy defects and hole defects are discriminated. In this context, Raman spectroscopy is introduced as a sensitive method for detecting and quantifying defects. Moreover, the visualization of in‐plane lattice defects by transmission electron microscopy (TEM) at atomic resolution is introduced. Understanding the type and density of defects in graphene oxide bears the potential for advancing the field of research while considering the specific types of defects as structural motifs.

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Section: Synthesis Of Graphene Oxidementioning

confidence: 99%

Defects in Graphene Oxide as Structural Motifs

2018

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“…Nishina et al 29 reported that KMnO 4 and H 2 SO 4 alone are sufficient to convert graphite to GO and NaNO 3 is not necessary to facilitate oxidation. Similarly, Tour et al 30 eliminated the utility of NaNO 3 by the introduction of H 3 PO 4 as a co-acid to H 2 SO 4 (1:9, v/v) in KMnO 4 (six equivalents)-mediated oxidation of graphite.…”

Section: Introductionmentioning

confidence: 99%

Control of Functionalities in GO: Effect of Bronsted Acids as Supported by Ab Initio Simulations and Experiments

et al. 2019

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Graphene oxide (GO) is an attractive precursor for graphene, provided by the well-known wet-chemical oxidative process. The intercalation of acid in graphite is considered as a crucial step, and its subsequent oxidation holds special relevance in synthesis. So far, the above chemistry is dominated by usage of H 2 SO 4 . Recently, H 3 PO 4 appeared as a suitable intercalant for graphite. However, its role is not well understood in the formation of GO, especially when present as a co-acid with H 2 SO 4 . Additionally, a relatively lower toxicity of H 3 PO 4 as compared to H 2 SO 4 , elimination of toxic NaNO 3 usage, and a facile purification protocol are encouraging in terms of low-cost production of GO with a reduced environmental impact. Here, we report the systematic synthesis and characterization of GOs prepared with the variation in the ratio of H 2 SO 4 and H 3 PO 4 . Ab initio simulations revealed that intercalation is primarily affected because of the usage of a mixture of co-acids. Interestingly, the ratio of the acids dictated the nature of the functionalities, extent of the defects, and morphology of the GOs, accounting for a pronounced effect on thermal stability, contact angle, zeta potential, and hydrodynamic size. The oxidation mechanism showed a predominance of H 2 SO 4 content, whereas H 3 PO 4 is found to mainly govern the intercalation of graphite, thereby affecting the acid-based intercalation–oxidation chemistry of graphite. The as-prepared GO suspension exhibited a high adsorption capacity for methylene blue dye removal in water, suggesting its potential as an adsorbent material in water treatment. The utility of the two acids affects the acid-based intercalation–oxidation chemistry of graphite and simultaneously may open up new opportunities for synthesized GOs, on tenets of green chemistry, in a wide arena of applications.

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“…This phenomenon indicates that the amount of sulfate group in GO firstly increases and then decreases under the harsh oxidation conditions. It has been reported that the sulfate group in GO is called organosulfate and is formed by hydrolysis of manganese esters in H 2 SO 4 during the oxidation process . They are predominantly covalently bound between two layers of carbon skeleton, as shown in Scheme (top right corner).…”

Section: Resultsmentioning

confidence: 99%

“…It has been reported that the sulfate group in GO is called organosulfate and is formed by hydrolysis of manganese esters in H 2 SO 4 during the oxidation process. 59 They are predominantly covalently bound between two layers of carbon skeleton, as shown in Scheme 1 (top right corner). In the subsequent hydrolysis step, it is cleaved to hydroxyl sulfate and then transformed to vicinal diols.…”

Section: Ftir Analysismentioning

confidence: 99%

Design of graphene oxide by a one‐pot synthetic route for catalytic conversion of furfural alcohol to ethyl levulinate

Shao

Jing

et al. 2019

J of Chemical Tech & Biotech

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Background Graphene oxide (GO) has abundant oxygen‐containing functionalities such as hydroxyl groups and carboxyl groups with distinct acidities. This feature makes GO a potential solid acid catalyst for the acid‐catalyzed reactions such as the production of ethyl levulinate (EL), a platform chemical, from the acid‐treatment of furfuryl alcohol (FA). The structure and functionalities of GO are closely related to its catalytic performance, and thus it is necessary to establish the relationship between the chemical structure and the catalytic properties of GO. To achieve this aim, in this work, the GO catalysts were designed by a facile one‐pot synthetic route with no subsequent modification. By controlling the parameters of oxidation process in preparation, multiple functional groups were immobilized onto graphitic substrate, significantly impacting the catalytic activity of GO in the conversion of FA to EL in an ethanol (EtOH) medium. Results The results showed that, the oxidation process significantly influenced the distribution of oxygen‐containing functionalities on the surface of GO. The amount of the oxygen‐containing functionalities can be adjusted by the oxidation parameters such as oxidizing agent equivalent, reaction time and temperature, while the organosulfate can only be remained at a moderate oxidation temperature. The existence of the synergistic effect between the oxygen‐containing functionalities and the organosulfate functionalities promoted the catalytic activity of GO for the acid‐catalyzed conversion of FA to EL. Conclusions This work provides a new strategy of design and development of functional graphene‐based catalysts for the acid‐catalyzed reactions, and lays foundation of the practicability of GO in biomass conversion. © 2019 Society of Chemical Industry

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Real-Time, in Situ Monitoring of the Oxidation of Graphite: Lessons Learned

Cited by 79 publications

References 44 publications

Defects in Graphene Oxide as Structural Motifs

Defects in Graphene Oxide as Structural Motifs

Control of Functionalities in GO: Effect of Bronsted Acids as Supported by Ab Initio Simulations and Experiments

Design of graphene oxide by a one‐pot synthetic route for catalytic conversion of furfural alcohol to ethyl levulinate

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