Evaluation of Layered Graphene Prepared via Hydroxylation of Potassium‐Graphite Intercalation Compounds

Wada, Takuya; Yasutake, Takuya; Nakasuga, Akira; Kinumoto, Taro; Tsumura, Tomoki; Toyoda, Masahiro

doi:10.1155/2014/925253

Cited by 7 publications

(6 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The diffraction peak pairs at 22.0° and 29.6°, 20.2° and 30.6°, to 16.4° and 33.4° were identified in region c‐e , d‐f , and e‐f , respectively, upon discharging. The I c values are determined to be 12.10, 8.78, and 5.40 Ǻ, respectively, based on Equation . The stage indexes n are therefore identified as 3, 2, and 1 (Table S1, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Unraveling the Potassium Storage Mechanism in Graphite Foam

Liu

Yin

Tian

et al. 2019

Advanced Energy Materials

158

121

View full text Add to dashboard Cite

Potassium‐intercalated graphite intercalation compounds (K‐GICs) are of particular physical and chemical interest due to their versatile structures and fascinating properties. Fundamental insights into the K+ storage mechanism, and the complex kinetics/thermodynamics that control the reactions and structural rearrangements allow manipulating K‐GICs with desired functionalities. Here operando studies including in situ Raman mapping and in situ X‐ray diffraction (XRD) characterizations, in combination with density‐functional theory simulations are carried out to correlate the real‐time electrochemical K+ intercalation/deintercalation process with structure/component evolution. The experimental results, together with theoretical calculations, reveal the reversible K‐GICs staging transition: C ↔ stage 5 (KC60) ↔ stage 4 (KC48) ↔ stage 3 (KC36) ↔ stage 2 (KC24/KC16) ↔ stage 1 (KC8). Moreover, the staging transition is clearly visualized and an intermediate phase of stage 2 with the stoichiometric formula of KC16 is identified. The staging transition mechanism involving both intrastage transition from KC24 (stage 2) to KC16 (stage 2) and interstage transition is proposed. The present study promotes better fundamental understanding of K+ storage behavior in graphite, develops a nondestructive technological basis for accurately capture nonuniformity in electrode phase evolution across the length scale of graphite domains, and offers guidance for efficient research in other GICs.

show abstract

Section: Resultsmentioning

confidence: 99%

Unraveling the Potassium Storage Mechanism in Graphite Foam

Liu

Yin

Tian

et al. 2019

Advanced Energy Materials

158

121

View full text Add to dashboard Cite

show abstract

“…The flow rates were as follows: sheath gas-argon 40 dm 3 •min -1 and helium 27 dm 3 •min -1 , plasma gas-argon 15.5 dm 3 •min -1 . Two additional tests with n-decanol were also carried out under atmosphere enriched with 1 % (1 dm 3 •min -1 ) and 5 % (4.75 dm 3 •min -1 ) of oxygen added directly to the plasma gas. The experiments were conducted at the pressure of 70 ± 3 kPa.…”

Section: Plasma Decomposition Of Alcoholsmentioning

confidence: 99%

“…Nowadays, the exfoliation of graphite can be carried out using alkali metals, e.g. potassium [3] or lithium [4]. Moreover, graphite can be also exfoliated in carbon arc discharge under hydrogen atmosphere [5][6].…”

Section: Introductionmentioning

confidence: 99%

Continuous and catalyst free synthesis of graphene sheets in thermal plasma jet

Fronczak

Fazekas

Károly

et al. 2017

Chemical Engineering Journal

View full text Add to dashboard Cite

Herein we present a continuous and catalyst free method for the synthesis of graphene sheets from aliphatic alcohols in a radiofrequency thermal plasma jet. Nine aliphatic linear alcohols (ethanol-decanol) were tested as possible precursors for the massive production of graphene sheets. Moreover, additional tests were also carried out with the inclusion of gaseous oxygen in order to promote the formation of graphene and to eliminate the unwanted carbon byproducts. The obtained materials were investigated by electron microscopy, Raman and infrared spectroscopy. The thermal stability of products was also evaluated using thermogravimetry. The surface chemistry features were analyzed using acid-base titration and X-ray photoelectron and IR spectroscopy. Finally, the adsorption performance of graphene sheets was tested in the removal of 4-chlorophenol from aqueous solutions. The highest content of graphene sheets was found in the product obtained from ethanol with the production rate of ca. 1.5 g/h. The plasma processing of higher alcohols yielded a mixture of graphene sheets and spherical carbon nanoparticles.

show abstract

“…The alkali-metal ions, such as K ions, are arranged with a particular stoichiometry on the graphene plane along with the GIC stage, as seen in Figure a (vi and v) when the metal ions are intercalated between the graphite interlayers. − , A gallery image of the K ion in KC 8 is shown in part iv, but when exposed to ambient conditions, the intercalated K ions are partially deintercalated, resulting in a lower stage because KC 8 is unstable in air. Therefore, the change to a lower level, such as KC 24 , changes the arrangement of K into the form shown in Figure a (ii and v). , Additionally, when K metal is intercalated between graphite layers in the form of K ions, electrons are donated from the K side to adjacent C atoms; therefore, the reductive electron-rich C due to the change in the charge density in the intercalated graphene layer is actively involved in the oxidation reaction during hydrolysis in water. According to the charge-density difference of KC 24 obtained by density functional theory (DFT) calculation, the yellow parts in Figures a (vi) and S1 show an increased charge density, and these parts are relatively advantageous for the occurrence of oxidation.…”

Section: Resultsmentioning

confidence: 99%

“…According to the charge-density difference of KC 24 obtained by density functional theory (DFT) calculation, the yellow parts in Figures a (vi) and S1 show an increased charge density, and these parts are relatively advantageous for the occurrence of oxidation. In the meantime, when K-GICs are exfoliated in water, O radicals or hydroxyl ions/radicals are formed when K ions react with water molecules. ,− Therefore, it can be predicted that the attack of O radicals or hydroxyl ions/radicals may occur in the regions where the charge density of the graphene layer is changed. In the case of KC 24 , because the graphene regions charged by K ions have a shape surrounding seven sp 2 C hexagons, selective oxidation is induced in these regions, enabling the formation of monodisperse subdomains of seven sp 2 C hexagons, which have a band gap corresponding to blue-light emission (Figure b).…”

Section: Resultsmentioning

confidence: 99%

Blue Graphene Quantum Dots with High Color Purity by Controlling Subdomain Formation for Light-Emitting Devices

Yoon

Kim

et al. 2020

ACS Appl. Nano Mater.

View full text Add to dashboard Cite

As an alternative to Cd-free quantum dots (QDs), graphene quantum dots (GQDs) have potential because of their various advantages, such as color tunability, nontoxicity, cost effectiveness, and photostability. However, realization of a useful blue emission from GQDs requires a narrower full width at halfmaximum (FWHM) and color purity in Commission Internationale de l'Eclairage (CIE) coordinates for display applications. These emission characteristics are strongly dependent on precise control of the sp 2 C subdomain, considered as the band-gap origin of GQDs. Here, we report a preparation for blue GQDs with improved color purity obtained from KC 24 graphite intercalation compounds. The as-synthesized KC 24 -GQD exhibits high color purity with a photoluminescence FWHM of 70 nm and CIE coordinates of (0.159, 0.082), which can be attributed to the controlled oxidation of graphene by intercalated K ions with an arrangement of KC 24 surrounding seven sp 2 C hexagons favorable for the formation of uniform subdomains. Furthermore, intrinsic emission-dominant fluorescence and phosphorescence from a powdered KC 24 -GQD-dispersed boron oxynitride matrix, as well as from solution-based KC 24 -GQD, prove its applicability to various lightemitting devices.

show abstract

Evaluation of Layered Graphene Prepared via Hydroxylation of Potassium‐Graphite Intercalation Compounds

Cited by 7 publications

References 15 publications

Unraveling the Potassium Storage Mechanism in Graphite Foam

Unraveling the Potassium Storage Mechanism in Graphite Foam

Continuous and catalyst free synthesis of graphene sheets in thermal plasma jet

Blue Graphene Quantum Dots with High Color Purity by Controlling Subdomain Formation for Light-Emitting Devices

Contact Info

Product

Resources

About