Patent Application
20170260055
The present disclosure relates to the field of industrial methods of preparing graphenes and a new multi-step process for preparing graphene with controlled characteristics by thermal exfoliation/reduction of graphite oxide.
Graphene and graphene-based materials have attracted a great deal of interest due to their fascinating properties and potential applications (Park S, Ruoff, R S. Nat Nanotechnol 2009; 4: 217-24). The exfoliation of graphite oxide to yield graphene oxide followed by a reduction process offers a simple method to obtain graphene (Marcano D C, Kosynkin D V, Berlin J M, Sinitskii A, Sun Z, Slesarev A, et al. ACS Nano 2010; 4: 4806-14; and Gao X, Jang J, Nagase S. J Phys Chem C 2010; 114: 832-42). This method has the advantage of being readily scalable and also has the ability to produce graphene materials with a tuneable amount of oxygen, depending on the characteristics of the parent graphite (Botas C, Álvarez P, Blanco C, Santamaría R, Granda M, Ares P, et al. Carbon 2012; 50: 275-82) and of the experimental conditions of both oxidation and reduction (Stankovich S, Dikin D A, Piner R D, Kohlhaas K A, Kleinhammes A, Jia Y, et al. Carbon 2007; 45: 1558-65). Other important properties, such as specific surface, cannot however be tuned. Several processes have been considered for the reduction of graphene oxide. These include: i) chemical reduction with different reagents, hydrazine being the most common (Menéndez, R. et al. RSC Adv., 2012, 2, 9643-9650); ii) thermal reduction which can be microwave assisted or performed in different atmospheres (argon, vacuum, hydrogen, hydrogen/argon) (Kaniyoor, A, Baby T T, Arockiadoss T, Rajalakshmi N, Ramaprabhu S., J Phys Chem C 2011; 115: 17660-9); iii) electrochemical reduction (Sundaram R S, Gomez-Navarro C, Balasubramanian K, Burghard M, Kern K., Adv Mater 2008; 20: 3050-3) and iv) a combination of different methods, such as chemical reduction/thermal annealing or thermal reduction/hydrogenation.
In the case of the thermal reduction it should be taken into account that the process is a thermal decomposition of the graphene oxide in which the bound oxygen is liberated in form CO and CO2, that are oxidation products of carbon, and the remaining carbon is reduced. The thermal exfoliation/reduction of graphite oxide is an interesting alternative to chemical reduction for the preparation of graphene materials because of: i) its simplicity, since the exfoliation of the graphite oxide to produce graphene oxide and its thermal reduction to graphene occurs all in one step; ii) its sustainability, since it avoids the use of environmentally unfriendly chemicals; and iii) its scalability. However, the efficiency with which graphene single sheets can be prepared by the thermal expansion of graphite oxide and the quality of the graphene sheets is dependent on the degree of oxidation of the graphite and the conditions of the thermal treatment. One of the requirements is to build up enough pressure during heat treatment stages (McAllister M J, Li J L, Adamson D H, Schniepp H C, Abdala A A, Liu J, et al., Chem Mater 2007; 19: 4396-404).
There are several methods described in the literature to produce the thermal treatment of graphite oxides. Most of them are focused on the control of the reduction degree of the graphenes obtained, main objective of the treatment. However, for certain applications, it is not only a requirement to obtain a reduction degree (essential property) but also to control other properties for this specific graphene reduced up to the desired temperature. This is the case of the surface area, essential property in applications such as energy storage devices (e.g. batteries, capacitors), or the solubility properties, which must be enhanced for catalytic applications.
Most of the treatments described in the literature focus on the thermal heating of the graphene sample in a single step up to the desired temperature. Most of the examples also suggest (or even analyze) that by modifying the final temperature of the single-stage treatment the reduction degree of the obtained graphene can be controlled. This documents are however silent about other important properties (e.g. BET surface area or processability issues). This is the case of the Rapid heating (on a hot plate) to a temperature of 400° C. in a single step, which has been used to obtain bulk quantities of single functionalized graphene sheets from a flake graphite oxide, and which showed problems of processability (Potts, J, et al. Composites science and technology 74 (2013) 166-172). Menéndez, R. et al., in Carbon 52 (2013) 476-485 describe the thermal exfoliation/reduction of oxide graphite at temperatures of 127° C., 300° C., 400° C., 600° C., 700° C., 800° C. and 1000° C. using a slow heating rate of 5° C./min with the objective of minimizing distortion of the sheets. The authors have also observed that high heating rates of 30° C./min produced more wrinkled sheets and the exfoliation was lower. In general terms, low BET surface were reported for this methodology. A further example is the thermal flash heating up to 1050° C. in a sealed tube (McAllister, M. J. et al., chem. Mater. 2007, 19, 4396-4404), in which graphene with high BET surface area are obtained. No mention about solubility issues is however mentioned.
In any case, the use of a single step does not allow tuning the properties of the graphenes obtained; once the final temperature is fixed, it leads to a fixed properties (C/O ratio, BET surface area, processability issues), without the possibility of controlling them separately.
In an attempt to prepare graphenes with controlled characteristics Zhang et al. (Zhang Y et al. Carbon 54, 2013, 143-148) make use of a sequential thermal treatment consisting of an initial stage of low thermal temperature exfoliation at 700° C. using a fast heating ramp (with a heating rate 100° C./min) followed by a second thermal treatment where the reduced graphene oxide sheets are annealed at 1500° C. and 40 MPa uniaxial pressures for 5 min in vacuum. The obtained graphenes show a low amount of residual oxygen (no D peak was detected in the Raman spectrum). This graphene is unappropriate for batteries and other devices, were the presence of a certain amount of oxygenated functional groups is beneficial and, additionally, were a larger surface area of the reduced samples and an adequate processability (suspension properties in certain solvents) are also a requirement.
US 2011/0157772 is directed to a process for preparing modified graphene by including spacers in its structure. It discloses a process wherein a graphitic material (fibers) is heated in a pre-heated furnace at temperature of 600° C. for 30 seconds, and subsequently at 1,100° C. for 20 minutes.
Angela D. Lueking et al. in Carbon, 2005 (vol. 109), pages 12710-12717 discloses process which comprises rapidly heating graphite oxide at 700° C. for two minutes, and then heating at 1,000° C. for 36 h.
Zhang Chen et al in Carbon, 2013 (vol. 62), pages 11-24 discusses among other things processes to exfoliate graphite oxide at low temperature under high vacuum.
There is thus a need to provide alternative and improved graphenic materials.
The present inventors have now surprisingly found that it is possible to prepare thermally reduced graphene in a controlled manner by way of a new synthetic process. The resulting graphene presents not only a controlled residual oxygenated functional groups portion (direct consequence of the final temperature selected in the treatment) but also a controlled surface area, which relates also with its volume.
Even further, the graphenes obtained by the process of the disclosure show a surprisingly high capacity to be dispersed in solvents, and thus have an excellent processability.
Among other properties, the obtained graphenes also show very good reconstruction of the carbon structure with temperature, which makes them very appropriate for diverse applications, like in batteries.
Thus, in one aspect the disclosure relates to a new multi-step process for the preparation of graphene which comprises the following steps:
In another aspect the disclosure relates to the graphene obtained by this multi-step process.
Throughout the present disclosure, graphenes are labeled according to the nomenclature Y-GO-X-T, wherein Y is either SS (single step) or MS (multistep), GO indicates Graphite Oxide. X indicates the origin of the graphite, wherein S indicates “synthetic”, C indicates “commercial”, CC indicates “combustion coke” and P is “petroleum coke”. T indicates the temperature at which graphene is obtained. For single step graphenes (SS), only one temperature is indicated, and for multi-step processes (MS) a first temperature is indicated corresponding to the first heating temperature, followed by “/” and the second heating temperature.
According to a particular embodiment, the process for the preparation of graphene further comprises a cooling step a′), between steps a) and b). In another particular embodiment, the process for the preparation of graphene of the present disclosure comprises:
a) flash thermal treatment of a graphite oxide at a temperature comprised between 90° C. and up to 700° C. sufficient to produce exfoliation and under inert atmosphere;
b) cooling the material obtained in the previous step at a temperature below 40° C.; and
c) heating the material obtained in the previous step above 700° C. and up 3000° C. under inert atmosphere at a heating rate between 2° C./min and 10° C./min.
The step of cooling the graphene oxide b) is carried out to a temperature below the temperature reached in the previous step a). The cooling temperature may vary always being less than disclosure 90° C. Typically, cooling can be done down to ambient temperature. In the present disclosure ambient temperature refers to a temperature typically below 40° C., for example between 10° C. and 30° C.
The term “flash thermal treatment” throughout the present disclosure is understood as a treatment wherein the sample is put in contact with a system preheated to the temperature indicated. For example, if treated in an oven, the flash thermal treatment according to the present disclosure comprises heating the entire oven volume to the temperature indicated and then introducing the sample so that is suddenly presented with such temperature.
According to a particular embodiment, the flash thermal treatment is carried out at a temperature greater than 90° C., preferably greater than 120° C. Exfoliation does not usually take place in a linear fashion with temperature, but there is typically a critical temperature (“explosion temperature”) at which the gases formed by the decomposition of graphite oxide are released suddenly resulting in most of the exfoliation of the material. Different graphite oxides have different explosion temperatures which can be determined by the skilled person. As the temperature of the flash thermal treatment increases with respect to that of the explosion temperature, a graphene with higher BET values is usually obtained. Thus, the process of the disclosure can lead at will to graphenes with high BET values and low reduction, as well as to graphenes with low BET values and high reduction, while providing at the same time excellent stability of dispersions thereof and processability. In another particular embodiment the flash thermal treatment is carried out at a temperature greater than 300° C., more particularly greater than 450° C. In a particular embodiment the flash thermal treatment is carried out at 460° C. In a further particular embodiment, the temperature in step a) is set between 100 and 700° C., particularly, between 300 and 600° C. In a further particular embodiment, the temperature in step a) is set between 100 and 250° C.
According to a particular embodiment, flash thermal treatment can take place in an especially designed reactor as the one illustrated in
This reactor allows carrying out step a) of the process of the disclosure, the exfoliation of graphite oxide into graphene oxide, in a semicontinous mode.
According to an embodiment, said reactor comprises an inlet (1) suitable for the addition of grafite oxide, said inlet (1) being separated from a preheated volume (2), which comprises an oven (3) connected to a discharge valve (4), by an inlet valve (8), and wherein said heated volume (2) is connected to a gas inlet (6) and a gas outlet (7), and in contact with heating means (5), said discharge valve (4) being connected to discharge means (9) [not shown] where the exfoliated material is recovered, and optionally allowed to cool. The reactor is under inert atmosphere in order in order to avoid undesired fire.
The graphene oxide is introduced in the inlet (1) of the reactor and through the inlet valve (8) reaching the preheated volume (2) where the flash thermal exfoliation takes place. The inventors have observed that in order to achieve an adequate exfoliation, it is important to introduce the graphite oxide in a preheated area, so that the graphite oxide is suddenly submitted to a temperature of up to 700° C. Also the relation between the mass (grams) of graphene oxide introduced in the reactor and the volume (cm3) of the preheated volume (2) can be advantageously controlled. The preheated volume (2) is preheated by conventional means in the oven (3). The nature of said heating means is not critical and typically involves an electric heating system. After the exfoliation, the graphene oxide is discharged through a discharge valve (4) ready to be submitted to steps b) and c). Residence times in the reactor are typically between about 2 and about 10 minutes depending on the applied temperature, in particular about 5 min.
According to a particular embodiment, step c) is carried out at a temperature comprised between 800° C. and 2,800° C., more particularly between 900° C. and 2500° C., even more particularly between 1000° C. and 2000° C. In a further embodiment the temperature of step c) is carried out at a temperature comprised between 400° C. and 1200° C., more particularly between 450° C. and 1050° C., more particularly between 500° C. and 1000° C. and even more particularly between 600° C. and 1000° C. This step can be carried out in a graphite oven with heating rates that vary between 1 and 15° C./min, more particularly between 2 and 10° C./min, for example 3° C./min, 4° C./min, 5° C./min, 6° C./min or 7° C./min.
The process of the disclosure is carried under inert atmosphere which may be achieved by introducing any inert gas like N2, Ne, Ar, etc. In a particular embodiment step a) is carried out under a N2 atmosphere, with flows between 50 and 300 mL/min, and step c) is carried out in an Ar atmosphere with flows between 2 and 4 L/min.
According to a particular embodiment, the ratio between the preheated volume and the graphite oxide added is comprised between 20-100 cm3/g. Such particular ranges provide the mass of graphite oxide inside the preheated volume of enough space to guarantee optimum exfoliation of the graphite oxide, minimizing the risk of an excessive stacking of the resulting graphene oxide.
In principle, any graphite oxide can be used as starting material in the process of the disclosure. According to a preferred embodiment, the graphite oxide is prepared from graphite by oxidation. Oxidation can be carried out by any of the well-known methods in the art like the Hummer's method (Hummers W S, Offeman R E. Preparation of graphitic oxide. Journal of the American Chemical Society 1958; 80: 1339-40) or a modified Hummer's method. It can be also prepared by other methodologies such as Brodie method (Brodie B C. Sur le poids atomique du graphite. Annales de chimie et de physique 1860; 59: 466-72), Staudenmaier method (L. Staudenmaier, Ber. Dtsch. Chem. Ges., 1898, 31, 1481), mild oxidation of graphite with different reactant (H2O2, etc.) (US patent application 20090028777). In a preferred embodiment, the graphite oxide is prepared by the Hummer's method or any modified Hummer's method, as illustrated in the Examples.
In turn, the graphite can be natural or synthetic graphite. In a particular embodiment the graphite used as starting material is commercial graphite, petrochemical graphite or semisynthetic graphite. The synthetic graphite can be obtained for example by graphitization of carbochemical, petrochemical or synthetic graphitizable carbonaceous precursors, such as coke, pitch or polymerized aromatic compounds. According to a preferred embodiment, graphite is obtained from coke by graphitization.
The graphene of the disclosure has been characterized by different methods as follows:
Elemental Analysis:
The carbon, hydrogen, sulphur and nitrogen contents of the samples were determined with a LECO-CHNS-932 microanalyzer. The oxygen content was obtained directly using a LECO-VTF-900 furnace coupled to the micro-analyzer. The proximate analysis was carried out following the ASTM D3174-04 Standard Test Method. All of the analyses were made using 1 mg of sample ground and sieved to <0.2 mm. The results were quoted as a mean of values from four determinations. In all cases, the standard deviation was found to be <0.5% of the absolute value. The results vary within certain ranges depending on facts like the type of graphite oxide used, the type of graphite, the reaction conditions for preparing the graphite oxide, and the thermal treatment temperatures.
Surface BET: The textural characteristics of the different samples were analyzed using N2 adsorption at 77 K. These analyses were performed in an ASAP 2020 Micromeritics equipment. The measurements were carried out following the ASTM standard D-6556 with a modification: before the experiments, the samples were outgassed at 350° C. for 10 h under vacuum (pressure below 10−3 Pa), using around 100 mg of sample in each experiment. The apparent surface area was determined from the N2-adsorption isotherm using the BET equation. The increased surface area of the graphene obtained by the process of the disclosure has been determined to be at least 100 m2/g, preferably 200 m2/g, more preferably 300 m2/g, even more preferably 400 m2/g and most preferably 500 m2/g.
Stability of dispersion of the graphenes in solvent: stability of dispersions of the different graphenes was evaluated by dispersing 10 mg of the graphene in 10 mL of DMSO at room temperature and 1 atm. After introducing in the ultrasound for 15 min, the suspension was left at room temperature and the presence of precipitate qualitatively evaluated. The corresponding graphene was considered to form stable dispersions if after 5 minutes no appreciable precipitation was observed.
Volume of the sample obtained: For comparative purposes of the volume occupied for a certain amount of graphene, digital images of the volume occupied for 22.5 grams of the obtained graphenes are shown in
The graphene of the disclosure presents among other characteristics, a controlled surface area, mainly as a factor of the temperature of initial flash pyrolysis step, while the subsequent step in ramp to the final temperature required to obtain the reduction desired does increase the surface area but not substantially. As a consequence of the control of the surface area, parameters as the volume occupying the sample or the possibility to disperse the sample in certain solvents are also established. These parameters (and their control) are crucial for diverse applications, like in batteries.
Even further, the graphenes obtainable by the process of the disclosure can form very stable dispersions in solvents, and therefore provide improved processability compared to other graphenes described in the literature. This is a very important feature for the preparation of pastes of graphene and to form homogeneous mixtures with other components, such as polymers, in order to provide materials with improved properties, a technology area currently of key interest.
For example, such processability can provide improved mixtures with spinels and other fillers in order to prepare improved and more homogeneous materials destined to store energy (e.g. batteries, supercondensers).The following examples are non-limiting and are merely representative of various aspects of the disclosure.
The present disclosure will be better understood from the following examples and more specifically by comparing the characterization of the samples produced by the preferred (but not limiting) embodiments of the multi-step procedure developed herein (examples 1, 3, 6, 7 and 8) and those resulted in the characterization of the same set of samples by thermally treatment at up to the same final temperature but by means of standard procedures described in the state of the art and reproduced herein (examples 2, 4, 5 and 9).
MS-GO-300/1000 was prepared by using as starting material a graphite oxide (GO-C) prepared from a commercial graphite using the modified Hummers' method described below.
Preparation of Graphite Oxide
This method makes use of the Hummers' reagents with additional amounts of NaNO3 and KMnO4. Concentrated H2SO4 (360 mL) was added to a mixture of graphite (7.5 g) and NaNO3 (7.5 g), and the mixture was cooled down to 0° C. by means of an ice bath. KMnO4 (45 g) was added slowly in small doses to keep the reaction temperature below 20° C. The solution was heated up to 35° C. and stirred for 3 h, at which point 3% H2O2 (1.5 L) was slowly added, giving rise to a pronounced exothermal effect up to 98° C. The reaction mixture was stirred for 30 min and, finally, the mixture was centrifuged (3700 rpm for 30 min), the supernatant being decanted away. The remaining solid material was then washed with 600 mL of water and centrifuged again, this process being repeated until the pH was neutral.
Preparation of MS-GO-C-300/1000
In a first step of flash thermal treatment, 0.3 g of GO-C were introduced in an oven having a volume of 25 cm3 previously heated at 300° C. under an atmosphere of N2 (100 mL min−1). The sample was then allowed to cool to room temperature. In a second step of thermal treatment the sample previously obtained was introduced in an oven and heated up to 1000° C. under an atmosphere of Ar (3 L min−1) at a heating rate of 5° C. min−1 to 700° C., the sample being kept at this temperature for 1 h. The sample so obtained was labeled as MS-GO-C-300/1000.
Characterization of MS-GO-C-300/1000
The obtained sample exhibits a fluffy appearance (
Preparation of SS-GO-C-1000
SS-GO-C-1000 was prepared by using as starting material the graphite oxide (GO-C) prepared in example 1. GO was thermally treated in an oven and heated up to 1000° C. under an atmosphere of Ar (3 L min−1) at a heating rate of 5° C./min, the sample being kept at this temperature for 1 h. The sample was labeled as SS-GO-C-1000.
Characterization of SS-GO-C-1000
SS-GO-C-1000 exhibits an appearance completely different form MS-GO-C-300/1000 (
The suspension of the sample in DMSO is not as homogeneous as MS-GO-C-300/1000 and it precipitates even after 5 min (
The C/O ratio, calculated by elemental analysis (Table 1) is 69, in the range of the expected for thermally treated samples at 1000° C. This value is a bit larger that for the sample obtained by a multiple-step.
The above results demonstrate the validity of the hypothesis that a multi-step procedure up to the same final temperature led to a reduced graphene with modified characteristics. Particularly a more stable suspension is obtained and the sample exhibit and enhanced SBET surface area. The reduction of the sample, although a bit larger in the case of the multi-step procedure, is in the range expected.
Preparation of MS-GO-P-460/700
MS-GO-P-460/700 was prepared by using as starting material a graphite oxide (GO-P) prepared by oxidation, using the Hummers method described in example 1, of a graphite, which itself was obtained by graphitization at 2800° C. of a petroleum coke. In a first step of flash thermal treatment, 0.3 g of GO-P were introduced in an oven having a volume of 25 cm3 previously heated at 460° C. under an atmosphere of N2 (100 mL min−1). The sample was then cooled to room temperature. In a second step of thermal treatment the sample previously obtained was introduced in an oven and heated up to 700° C. under an atmosphere of Ar (3 L min−1) at a heating rate of 5° C. min−1, the sample being kept at this temperature for 1 h. The sample so obtained was labeled as MS-GO-P-460/700
Characterization of MS-GO-P-460/700
The obtained sample exhibits a fluffy appearance (
Preparation of SS-GO-P-700
SS-GO-P-700 was prepared by using as starting material the graphite oxide (GO-P) prepared in example 3. GO-P was thermally treated in an oven and heated up to 700° C. under an atmosphere of Ar (3 L min−1) at a heating rate of 5° C. min−1, the sample being kept at this temperature for 1 h. The sample was labeled as SS-GO-P-700.
Characterization of SS-GO-P-700
SS-GO-P-700 (
From the results showed in examples 3 and 4 it can be seen that the process of the disclosure leads to a reduced graphene forming more stable suspensions and having larger SBET surface area.
We also demonstrate that the initial temperature of the initial thermal treatment can be modified to certain point to control de SBET surface area obtained.
Preparation of PseudoMS-GO-P-460Ramp/700
pseudoMS-GO-P-460ramp/700 was prepared by using as starting material the graphite oxide (GO-P) prepared in example 3. GO-P was thermally treated in an oven and heated up to 460° C. under an atmosphere of Ar (3 L min−1) at a heating rate of 5° C. min−1. The sample was then cooled to room temperature. In a second step of thermal treatment the sample previously obtained was introduced in an oven and heated up to 700° C. under an atmosphere of N2 (3 L/min) at a heating rate of 5° C./min, the sample being kept at this temperature for 1 h.
Characterization of PseudoMS-GO-P-460Ramp/700
pseudoMS-GO-P-460ramp/700 (
It can thus be seen that the multi-step procedure of the disclosure comprising an initial flash pyrolysis step) leads to graphenes with improved characteristics.
Preparation of MS-GO-P-300/700
MS-GO-P-300/700 was prepared by using as starting material the graphite oxide (GO-P) prepared in example 3. In a first step of flash thermal treatment, 0.3 g of GO-P were introduced in an oven having a volume of 25 cm3 previously heated at 300° C. under an atmosphere of N2 (100 mL min−1). The sample was then cooled to room temperature. In a second step of thermal treatment the sample previously obtained was introduced in an oven and heated up to 700° C. under an atmosphere of Ar (3 L min−1) at a heating rate of 5° C. min−1, the sample being kept at this temperature for 1 h. The sample so obtained was labeled as MS-GO-P-300/700.
Characterization of MS-GO-P-300/700
The obtained sample exhibits a fluffy appearance (
Preparation of MS-GO-P-400/700
MS-GO-P-400/700 was prepared by using as starting material the graphite oxide (GO-P) prepared in example 3. In a first step of flash thermal treatment, 0.3 g of GO-P were introduced in an oven having a volume of 25 cm3 previously heated at 400° C. under an atmosphere of N2 (100 mL min−1). The sample was then cooled to room temperature. In a second step of thermal treatment the sample previously obtained was introduced in an oven and heated up to 700° C. under an atmosphere of Ar (3 L min−1) at a heating rate of 5° C. min−1, the sample being kept at this temperature for 1 h. The sample so obtained was labeled as MS-GO-P-400/700
Characterization of MS-GO-P-400/700
The obtained sample exhibits a fluffy appearance (
Preparation of MS-GO-S-300/1000
MS-GO-S-300/1000 was prepared by using as starting material a graphite oxide (GO-S) prepared from a synthetic graphite, using the Hummers method described in example 1. In a first step of flash thermal treatment, 0.3 g of GO-S was introduced in an oven having a volume of 25 cm3 previously heated at 300° C. under an atmosphere of N2 (100 mL min−1). The sample was then cooled to room temperature. In a second step of thermal treatment the sample previously obtained was introduced in an oven and heated up to 1000° C. under an atmosphere of Ar (3 L min−1) at a heating rate of 5° C. min−1, the sample being kept at this temperature for 1 h. The sample so obtained was labeled as MS-GO-S-300/1000
Characterization of MS-GO-S-300/1000
The obtained sample exhibits a fluffy appearance (
Preparation of SS-GO-S-1000
SS-GO-S-1000 was prepared by using as starting material the graphite oxide (GO-S) prepared in example 8. GO-S was thermally treated in an oven and heated to 1000° C. under an atmosphere of Ar (3 L min−1) at a heating rate of 5° C. min−1, the sample being kept at this temperature for 1 h. The sample was labelled as SS-GO-S-1000.
Characterization of SS-GO-S-1000
SS-GO-S-1000 (
Preparation of MS-GO-S-400/1000
MS-GO-S-400/1000 was prepared by using as starting material a graphite oxide (GO-S) prepared from a synthetic graphite, using the Hummers method described in example 1. In a first step of flash thermal treatment, 0.3 g of GO-S was introduced in an oven having a volume of 25 cm3 previously heated at 400° C. under an atmosphere of N2 (100 mL min−1). The sample was then cooled to room temperature. In a second step of thermal treatment the sample previously obtained was introduced in an oven and heated up to 1000° C. under an atmosphere of Ar (3 L min−1) at a heating rate of 5° C. min−1, the sample being kept at this temperature for 1 h. The sample so obtained was labeled as MS-GO-S-400/1000
Characterization of MS-GO-S-400/1000
The obtained sample exhibits a fluffy appearance. The suspension of MS-GO-S-400/1000 in DMSO is homogeneous and stable after 5 min. The C/O ratio calculated for this sample is 129 (Table 1), similar to other samples heated at this temperature. The SBET surface area calculated for this sample was ≈355 m2g−1 (Table 1).
| Number | Date | Country | Kind |
|---|---|---|---|
| 14382352.4 | Sep 2014 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/071367 | 9/17/2015 | WO | 00 |
