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Partial DOS of the unit cells C24F12 hex, C24F12Br2 No. 1 and No. 2 with the chain-like and molecular arrangement of embedded Br2, respectively.
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The prospects of the complementary use of X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) have been demonstrated by the examples of highly oriented pyrolytic graphite, half-fluorinated graphite C2F, and half-fluorinated graphite C2F intercalated with Br C2FBr0.15. It has been shown that the photoelectron energy losses in...
Citations
Recently, Ti3C2 MXene with facile physicochemical properties is a fascinating candidate material for energy storage applications. Herein, solvothermal method was employed to fabricate the novel d-Ti3C2/MoO3@IL by incorporation of imidazolium based ionic liquid to MoO3 nanorods (MoO3@IL); which was intimately anchored onto the surface of d-Ti3C2 MXene. Additionally, this d-Ti3C2 MXene acts as a promising conductive substrate not only to maintain structural stability, but maintains the electrophilicity of electroactive centers as well. Similarly, MoO3@IL improves electrical conductivity due to ionic liquid, and improves reaction kinetics by supplying effective channel for charge transport system with improved pseudocapacitance. Owing to the intimate interaction, the d-Ti3C2/MoO3@IL electrode exhibited exceptional electrochemical performances with specific capacitance of 1680 F g–1 at 1 A g–1, outstanding rate performance, and excellent cyclic stability. Moreover, the symmetric supercapacitor (SSC) device from d-Ti3C2/MoO3@IL demonstrated excellent energy densities of 41 Wh kg–1 and 9.6 Wh kg–1 at power densities of 990 W kg–1 and 3456 W kg–1 respectively. We have employed this novel hybrid electrode material for SSC device application for the first time. The results proved that d-Ti3C2/MoO3@IL is an advanced electrode material, and this scheme provides the valuable method to fabricate MXene and ionic liquid based electrodes with superior electrochemical performance for supercapacitors.
The interlayer space of 2D materials can be a slit reactor where transformations not typical for the gas phase occur. We report redox reactions involving acetonitrile and nitrogen oxide guests in galleries of fluorinated graphite. Fluorinated graphite intercalation compounds with acetonitrile are treated with dinitrogen tetraoxide and the synthesis products are studied by a set of experimental methods. Data analysis reveals that N2O4 dissociates in fluorinated graphite matrices to form nitrogen-containing species NO3, NO2, NO, and N2. The interaction of NO3 with acetonitrile yields HNO3, which predominates as a guest in the synthesis products independently of the fluorination degree of the matrix. This reaction is accompanied by the removal of fluorine atoms weakly bonded to the graphite layers, leading to partial defluorination of the matrices. Our work demonstrates the possibility of using fluorinated graphite as a test nanoreactor whose dimension can be controlled by fluorination of the layers.
The possibility to obtain novel data by standard electron spectroscopy and quantum chemical techniques is exemplified by C2FBr0.15 intercalate and silver foil. The features of extended X-ray photoelectron spectra are interpreted by electronic transitions in the valence band of similar unit cells. The analysis of experimental and calculated spectra reveals two states of intercalated Br2: molecular and chain-like. The interaction of Ag with NO2 at 300–520 K is limited by the formation of an oxidized state in the near-surface layer with a thickness of ∼6 A, with the metallic state of silver dominating in the Ag3d И Ag MNN spectra. Geometric parameters, states of atoms, and the character of bonds between them are consistent with the previously obtained results.
Despite decades of study the precise behavior of bromine in graphitic carbons remains unclear. In this report, using Raman spectroscopy , we reveal two types of bromine structure in graphitic carbon materials. Between fluorinated graphene layers with a composition close to C2F, Br2 molecules are intercalated in a form similar to liquid bromine. Bromination of pristine and low-fluorinated graphitic carbons behaves very differently with distinct Br-related Raman spectra. With the guidance of density functional theory (DFT) calculations, all Raman features are assigned to normal vibration modes of specific bromine species over graphene and fluorinated graphene. When intercalated between extended non-fluorinated sp2-hybridized carbon regions, physisorbed Br2 molecules move freely across the non-functionalized region toward the CF border. Multiple Br2 molecules then combine spontaneously into Br3-based chains, whose coupling activates otherwise Raman inactive modes. Significant charge transfer to bromine species occurs in this case. DFT calculated frequencies match precisely the experimental Br-related Raman bands observed in the intercalation carbon compounds. The fluorine-catalyzed bromine chain-formation process shown here is general and should also operate with edges and other defect species.
