Effect of oxygen and structural properties on the electrical conductivity of powders of nanostructured carbon materials

Abstract

This work reports a study of the electrical conductivity under compression of nanostructured carbon powders with different physicochemical properties (texture, chemical-surface and morphology): a commercial carbon black (Vulcan XC-72R) and synthesized ordered mesoporous carbon (OMC), carbon nanocoils (CNC) and carbon nanofibers (CNF). The electrical conductivity was determined from the sample resistance under compaction (from 0.5 to 140 MPa) using the four-probe technique. A comparison of intrinsic and grain electrical conductivities (calculated according to the percolation theory and the general effective media approximation) was performed. Additionally, samples were subjected to chemical oxidation or graphitization treatments to evaluate the effect of oxygen content and structural properties on the electrical conductivity. In spite of the physicochemical differences of carbon materials, an exponential decrease of the electrical conductivity with the oxygen amount was stated. Finally, thermal treatment of OMC at 1500 °C led to a surprising increase in its conductivity due to the graphitization of the amorphous carbon structure of the original material and the oxygen removal.

Electrochemical oxidation of ordered mesoporous carbons and the influence of graphitization

“…As-synthesized OMC were subjected to a heat treatment at 1500 ºC for 1 h in a graphite electrical furnace (heating rate 10 ºC min -1 ) under Ar flow [27,51]. This temperature (1500 ºC) has been found to favor the development of a crystalline carbon framework without a significant impact on the mesoporous structure of OMC [27,31,51].…”

“…The atomic composition of OMC was studied by XPS. C1s spectra were deconvoluted in four contributions by Gaussian/Lorentzian fitting [51,52,57]: i) sp 2 graphitic carbon (C=C) and sp 3 hybridized carbon (C-C) were combined in an asymmetric peak at 284.5 ± 0.0 eV [51,52,57], ii) C-O bonds in hydroxyls (C-OH) or epoxides (C-O-C) at 286.7 ± 0.3 eV, iii) C=O bonds in carbonyls (C=O) or carboxyl (O=C-OH) at 288.9 ± 0.2 eV and iv) π-π* shake up satellite contribution at 290.9 ± 0.0 eV ( Figure S1). The atomic compositions, calculated from the survey and the deconvoluted XPS C1s spectra analysis, are summarized in Table 2.…”

Capacitance Enhancement of Hydrothermally Reduced Graphene Oxide Nanofibers

“…Carbon nanofibers (CNFs), composed entirely of graphite stacks of small lateral size in a 1D filament morphology, present a unique structure that combines properties such as electronic conduction, thermal and chemical resistance, low mass density and good specific surface area, which are essential for a wide range of potential applications. In this sense, CNFs have been used for many different applications, such as heterogeneous catalysis, conversion or storage of electrochemical energy, sensors, electronic devices, and structural and conductive composite materials [1][2][3][4][5][6][7]. In the case of electrochemical energy storage, the high electrical conductivity of CNFs in combination with their accessible porosity allows satisfactory charge accumulation but lower than that offered for graphene materials [8,9].…”

“…In the case of electrochemical energy storage, the high electrical conductivity of CNFs in combination with their accessible porosity allows satisfactory charge accumulation but lower than that offered for graphene materials [8,9]. Graphene is the basic structural unit of the most conductive nanocarbon materials including graphite and carbon nanofibers and nanotubes since it exhibits a free movement of π-electrons along with the 2D network of conjugated sp 2 -carbon, allowing it to achieve ultrahigh electrical conductivities (10 5 -10 6 S•m −1 ) [7,10]. Graphene has already been used in all possible electrochemical devices with remarkable results [11], whereas expanded graphite presented a large volumetric capacitance (177 F•cm −3 ) in aqueous acid media [12].…”

Synthesis of Ag nanoparticles/ordered mesoporous carbon as a highly efficient catalyst for the electroreduction of benzyl bromide

“…[21][22][23] The crystallinity and conductivity of carbon materials can be improved by heat treatment or by the use of graphitization catalysts. 24,25 As a mesoporous material (diameter ¼ 2-50 nm), OMC is a good support or container for the deposition of metal nanoparticles, resulting in outstanding mass transfer performance of reactants and products. 26,27 Therefore, OMC has good application prospects as an electrode material in electrosynthesis.…”