Phenol dissociation on pristine and defective graphene

Phenol (C6H5O‒H) dissociation on both pristine and defective graphene sheets in terms of associated enthalpic requirements of the reaction channels was investigated. Here, we considered three common types of defective graphene, namely, Stone-Wales, monovacancy and divacancy configurations. Theoretical results demonstrate that, graphene with monovacancy creates C atoms with dangling bond (unpaired valence electron), which remains particularly useful for spontaneous dissociation of phenol into phenoxy (C6H5O) and hydrogen (H) atom. The reactions studied herein appear barrierless with reaction exothermicity as high as 2.2 eV. Our study offers fundamental insights into another potential application of defective graphene sheets

Phenol Dissociation on Pristine and Defective Graphene

Phenol (C6H5O‒H) dissociation on both pristine and defective graphene sheets in terms of associated enthalpic requirements of the reaction channels was investigated. Here, we considered three common types of defective graphene, namely, Stone-Wales, monovacancy and divacancy configurations. Theoretical results demonstrate that, graphene with monovacancy creates C atoms with dangling bond (unpaired valence electron), which remains particularly useful for spontaneous dissociation of phenol into phenoxy (C6H5O) and hydrogen (H) atom. The reactions studied herein appear barrierless with reaction exothermicity as high as 2.2 eV. Our study offers fundamental insights into another potential application of defective graphene sheets

Microwave exfoliated graphene-based materials for flexible solid-state supercapacitor

Herein, we report the simultaneous exfoliation and reduction of graphene oxide (GO) and graphene nanoplatelets (GNPs) by rapid microwave irradiation, to overcome the hurdles of their low electrical conductivity and tendency to restack, and realize their full potential as supercapacitor electrode materials. After microwave treatment, the ID/IG value of the microwaved GO (MW-GO) increased by 0.11, whereas the I2D/IG value of the microwaved GNPs (MW-GNPs) decreased by 0.48, revealing that the graphene-based materials were reduced and exfoliated as observed in the Raman spectra. Morphological studies revealed a porous structure of MW-GO and loose stacked layers of MW-GNPs, which showed the exfoliation of the graphene-based materials. A supercapacitor device was constructed using a mixture of MW-GO, MW-GNPs, and polypyrrole and yielded a specific capacitance value of 137.2 F g−1 with a cycling stability of 89.8% after 1000 charge/discharge cycles. The electrochemical performance of the device remains unchanged when bent continuously at 180° because the cyclic voltammetry and galvanostatic charge/discharge curves remained the same after 50 bending repetitions. Therefore, the simultaneous reduction and exfoliation of these graphene-based materials by rapid microwaves provides a promising route for the scalable and cost-effective preparation of supercapacitor electrode materials

Functionalized graphene oxide-reinforced electrospun carbon nanofibers as ultrathin supercapacitor electrode

Graphene oxide has been used widely as a starting precursor for applications that cater to the needs of tunable graphene. However, the hydrophilic characteristic limits their application, especially in a hydrophobic condition. Herein, a novel non-covalent surface modification approach towards graphene oxide was conducted via a UV-induced photo-polymerization technique that involves two major routes; a UV-sensitive initiator embedded via pi-pi interactions on the graphene planar rings, and the polymerization of hydrophobic polymeric chains along the surface. The functionalized graphene oxide successfully achieved the desired hydrophobicity as it displayed the characteristic of being readily dissolved in organic solvent. Upon its addition into a polymeric solution and subjected to an electrospinning process, non-woven random nanofibers embedded with graphene oxide sheets were obtained. The prepared polymeric nanofibers were subjected to two-step thermal treatments that eventually converted the polymeric chains into a carbon-rich conductive structure. A unique morphology was observed upon the addition of the functionalized graphene oxide, whereby the sheets were embedded and intercalated within the carbon nanofibers and formed a continuous structure. This reinforcement effectively enhanced the electrochemical performance of the carbon nanofibers by recording a specific capacitance of up to 140.10. F/g at the current density of 1. A/g, which was approximately three folds more than that of pristine nanofibers. It also retained the capacitance up to 96.2% after 1000 vigorous charge/discharge cycles. This functionalization technique opens up a new pathway in tuning the solubility nature of graphene oxide towards the synthesis of a graphene oxide-reinforced polymeric structure

Electrospun graphene nanoplatelets-reinforced carbon nanofibers as potential supercapacitor electrode

The combination of graphene nanoplatelets and carbon nanofibers were successfully fabricated by utilizing a one-step solution based on the electrospinning technique. A distinctive morphology was observed in which the platelets were suspended between the fibrous structure that significantly improved the specific capacitance of the nanofiber to 86.11 F g−1, twice the increment from its original structure. Furthermore, all of the graphene nanoplatelets-reinforced samples recorded an optimal performance of over 90% capacitive retention after 1000 continuous charge/discharge cycles, regardless of the GnP concentration. These findings indirectly reflect the potential of CNF as the electrode material in the fabrication of high performance supercapacitor devices