Graphitization Of Amorphous Carbon Research Articles

Biocatalyst for carbon veil anode in microbial fuel cells: The effect of precursor and catalyst loading on overall performance

Biocatalysts in anodes have been crucial in improving microbial fuel cell (MFC) performance. Biocatalysts derived from biomass such as coconut wood sawdust (SD-B) and pepper processing residue (PS-B), were used to improve the electrocatalytic properties of Carbon Veil (CV) electrodes. The amorphous graphitic carbon biocatalyst with a mesoporous structure was found to have a surface area of 889.31 m2/g for SD-B and 763.56 m2/g for PS-B. Surface functional groups such as -OH which imparts hydrophilicity and -C=O and COOH which promotes bacterial compatibility have been revealed to be present in both catalysts. Catalyst loading played a major role and at an optimal loading of 2 mg/cm2, the electrodes exhibited maximum electrocatalytic activity in the case of both biocatalysts. The voltammetric capacitances of SD-B and PS-B modified electrodes were 191.6 mF/cm2 and 106.6 mF/cm2 demonstrating their pseudocapacitive behaviour too. The performance of MFC with SD-B revealed a maximum power density of 10.1 W/m3 (Open Circuit Voltage (OCV) of 850 mV), followed by PS-B at 6.89 W/m3 (OCV of 825 mV) whereas the plain CV was at 0.168 W/m3 (OCV of 760 mV). Anode polarization studies indicated reduced slopes for biocatalyst-modified anodes, signifying improved electrode kinetics, particularly notable in the SD-B modified MFC where the cathode became the limiting electrode. Coulombic efficiencies of the biocatalyst-modified MFCs increased to 54.50%, (SD-B 2 mg/cm2) and 37.78% (PS-B 2 mg/cm2) respectively from 12.74% as noticed in the case of unmodified MFC. This study emphasizes the potential of biocatalysts as a simple and low-cost means of enhancing the anode properties – porosity, conductivity, hydrophilicity, and biocompatibility.

3D lithiophilic collector coated by amorphous g-C3N4 enabling Ultra-Stable cycling Li metal batteries

Lithium metal batteries (LMB) are thought of the most promising candidates for the next generation of high energy density batteries, but the problems of interface instability and uncontrollable dendrite growth are key constraints to the commercial application. Herein, we constructed an amorphous graphitic carbon nitride (g-C3N4) “outerwear” modified lithiophilic 3D Au/CoO nanoarray matrix (CACM) as a multifunctional dual-layer host, achieving dendrite-free and cycling stabilized Li metal anode. The density functional theory (DFT) calculations show that the reaction between CACM and Li atoms has a strong binding energy and a large amount of charge transfer. The lithiophilic 3D host induces Li metal uniform deposition with a low nucleation barrier within the 3D skeleton. The amorphous g-C3N4 “outerwear” can effectively avoid direct contact between the electrolyte and Li and reduce the irreversible side reaction. Meanwhile, the g-C3N4 layer has abundant Li ion transport channels, which facilitated fast Li+ transfer and modulate the ion concentration over the anode surface. Thus, the half-cell equipped with the CACM electrode has ultra-high cyclic stability, maintaining a CE value of 99.6 % over 230 cycles at 1 mA cm−2 with 1 mAh cm−2. The symmetric-cell can maintain a low overpotential stable run 1300 cycles at 10 mA cm−2. Similarly, the full cell also showed outstanding long-term cycle stability (capacity maintained at 96.3 % after 400 cycles at 1C) and superior rate capability. The in-situ visualization cell test and ex-situ SEM also demonstrated that the multifunctional host inhibits volume expansion and the dendritic growth of Li.

Metal dependence of spontaneous graphitization growth at room temperature

The low-temperature graphene growth is a crucial step toward more efficient, cost-effective, productive, cheap, and sustainable energy systems. In this work, we report the effect of transition metal nanoparticles (TMNPs) Ag, Pd, and Cu on the graphitization of amorphous carbon (a-C) deposited onto SiO2 substrates using a one-step magnetron sputtering technique at room temperature (RT). Transmission electron microscopy (TEM), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) were used to examine the structures of TMNP-C films. The a-C around the metallic NPs spontaneously formed a disordered graphitic structure. Moreover, the 2D peak was detected in Raman spectra, and XPS analyses revealed the sp2 graphitization for the Ag-C, Pd-C, and Cu-C films deposited on the SiO2 substrates. These studies suggest that these metals’ graphitization activity is in the sequence of Pd > Cu > Ag. The highest catalytic activity of Pd NPs in graphitization at low temperatures was due to the highest carbon solubility and nano-sized particles. Thus, the control of the particle size of the catalyst to enhance the carbon solubility and decrease the melting point will open up a new strategy to grow high-quality graphene at low- temperatures.

In situ preparation of two-dimensional mortise and tenon structure g-C3N4/MoO3 photocatalyst for the reduction of aqueous Cr(VI)

In situ solid-state synthesis was employed to prepare the [Formula: see text] (CM) heterojunctions with a two-dimensional mortise and tenon structure. The prepared products were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy, suggesting that amorphous graphitic carbon was obtained. The photocatalytic performance of the prepared photocatalysts was evaluated in aqueous Cr(VI) reduction reactions under visible-light ([Formula: see text] > 420 nm) irradiation. The results of the experiments showed that the photocatalytic activity of CM is influenced by the composition of heterojunctions. The optimum photocatalytic activity for the photocatalytic reduction of Cr(VI) was found in the compound CM-25, which contains a 25% [Formula: see text] concentration. The Cr(VI) reduction rate on CM-25 was four times that of [Formula: see text] and 14.5 times that of [Formula: see text], the photocatalytic activity of CM-25 only dropped by 7.7% in four cycles. Scavenger investigations and EPR tests indicated that the major photogenerated radicals in the reduction of Cr(VI) were superoxide negative radicals (•[Formula: see text]) and hydroxyl radicals (•[Formula: see text]OH). CM-25 was discovered to be an S-scheme heterojunction that effectively suppressed photogenerated charge carrier recombination and retained photogenerated holes (in the valence band of [Formula: see text]) and electrons (in the conduction band of [Formula: see text]) with higher redox capabilities. CM-25 has potential applications in the photocatalytic reduction of Cr(VI) in wastewater.

Green Synthesis of Surface Modified Biochar for Simultaneous Removal of Steroidal Hormones and Heavy Metals from Wastewater: Optimisation by Central Composite Design

The modification of pristine biochar derived from the waste of sweet prickly pear using the green modification method to produce nano-sized biochar (nanobiochar) for the removal of steroidal hormones and heavy metals from water and wastewater is reported in this study. Based on the characterisation results using FTIR, Raman spectroscopy, and XPS, the material had (COOH), (C=O), and (OH) functional groups typical of graphitic amorphous carbon. The SEM-EDS and XRD results showed that the material was mesoporous and amorphous in nature. The BET analysis results revealed that the surface area significantly increased from 220.1 m2/g to 354.6 m2/g after the modification of the pristine biochar. Based on the TGA-DSC results, the material was thermally stable up to 550 °C. A complete factorial experimental design using Minitab 21 Statistical Software (version 18.1) was employed to optimise the experimental adsorption conditions. The F-values and p-values for the lack-of-fit of the model showed the acceptability and significance of the ANOVA model. The Freundlich adsorption isotherm was found to provide a better fit for the steroid adsorption data than the Langmuir adsorption isotherm, with moderate values of R2 ≥ 0.92 for Langmuir and R2 ≥ 0.95 for Freundlich, as well as maximum adsorption capacities of 14.53 mg/g, 10.58 mg/g, 12.50 mg/g, 5.73 mg/g, 5.63 mg/g, and 9.75 mg/g obtained for estriol, α-oestradiol, β-oestradiol, testosterone, progesterone, and bisphenol A. Freundlich R2 values were lower than Langmuir R2 values for metal adsorption, with maximum adsorption capacities of 8.58 mg/g, 4.15 mg/g, and 6.95 mg/g obtained for nickel, cadmium, and lead, respectively. The maximum percentage of removal for effluents and influents was between 84–89% and 78–86% for steroid hormones and heavy metals, respectively. The highest removal percentage between 90–95% was obtained for spiked ultrapure water for both steroid hormones and heavy metals. The material exhibited a removal percentage up to 60% after the first four cycles.

Carbon Microspheres with Cr(VI) Adsorption Performance were Prepared by In-situ Hydrothermal Carbonization Method

Biochar material is a renewable adsorbent widely used for treating contaminated wastewater. The hydrothermal carbon (HTC) were prepared from low polymeric sugars and low concentration glucose under hydrothermal carbonization reactions without using dispersants. The composition and structure of the biochar produced were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Raman spectroscopy (Raman), and N2 adsorption-desorption, indicating that amorphous graphitic carbon was obtained. Experimental results from the static adsorption of Cr(VI)-contaminated wastewater showed that HTCP-2 exhibited the highest adsorption capacity for Cr(VI), with a maximum adsorption capacity of 22.62 mg.g−1.The adsorption Cr(VI), MB, and RhB by the synthesized biochar all conformed to the pseudo-second-order kinetic model and Freundlich isotherm, suggesting a multilayer chemical adsorption process. Additionally, the synthesized HTC surface is enriched with a significant amount of oxygen-rich functional groups, which also has good adsorption performance for cationic dyes. Furthermore, the test results of fluorescence, photocurrent, and impedance indicate that HTCP-2 possesses the ability to generate and separate photoinduced charge carriers. This implied that HTCP-2 can be used for the preparation of adsorption photocatalysts, which effectively remove environmental pollutants through the synergistic effect of adsorption-photocatalysis. This study provides a research foundation for advancing water treatment technologies. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Tribo-induced catalytically active oxide surfaces enabling the formation of the durable and high-performance carbon-based tribofilms

Carbon-containing tribofilms have attracted significant interest in the lubrication research despite a scarcity of information on their high-temperature performance under severe boundary conditions. In this study, high-temperature lubrication of the carbon tribofilm produced from cyclopropane carboxylic acid (CPCa) and NiAl-layered double hydroxide (LDH) nanoparticles was evaluated. NiAl-LDH nanoparticles significantly enhanced the friction stability and antiwear performance of CPCa by over 90% at 50°C and 100°C, comparable to the benchmark zinc dialkyldithiophosphates (ZDDPs). The highly graphitic amorphous carbon tribofilms and the fine-grain intermediate tribolayer constructed by the thermal decomposition products of NiAl-LDH contributed to such excellent lubrication performance. This study paves a pathway in developing functional anti-wear additives for the durable and high-performance carbon-containing tribofilms at high temperatures.

Effect of hydrogen plasma treatment of nanodiamond on the tribological properties of polytetrafluoroethylene-based nanocomposite coating

ABSTRACT Carbon atom recombination and etching of the surface of nanodiamond (ND) by hydrogen plasma and their effects on the dispersion and the tribological properties of a polytetrafluoroethylene (PTFE) nanocomposite coating were investigated. The surface-modified ND samples subjected to plasma treatment were characterized using FESEM, HRTEM, Raman spectroscopy, FT-IR spectroscopy and XPS. The results showed that the plasma treatment facilitates etching and recombination of the ND surface and modifies the crystallinity of the graphitic amorphous carbon. The tribological properties of the PTFE-based nanocomposite coatings prepared with the modified ND depended on the content of sp 3 -bonded carbon on the surface and the crystallinity of the ND. Hydrogen plasma treatment caused a significant improvement in the dispersion and tribological properties of the PTFE/ND nanocomposite coating due to surface modification of the ND.

Ultra-light-weight microwave X-band EMI shielding or RAM material made from sustainable pyrolysed cork templates.

Cork is a renewable and sustainable material, highly porous and lightweight. We valorised waste cork and recycled wine stoppers to make pyrolysed/carbonised solid cork, for use as economic and sustainable microwave (MW) absorbers at the microwave X-band (8-12 GHz), without binder or additives. Although cork is already a very lightweight material (0.16 g cm-3), the pyrolysed cork is five-times less dense at 0.031 g cm-3, was amorphous graphitic carbon, and had an excellent shielding effectiveness (SET) of -18 to -38 dB, depending on thickness, with attenuation of the electromagnetic energy through internal reflection within the cellular cork structure. Furthermore, this ultra-light-weight material has an extremely high MW specific shielding effectiveness or efficiency (SSE), between -640 to -1235 dB g-1 cm3 over the entire X-band range, depending on thickness (3.0-8.6 mm), one of the highest reported for any pure carbon material, this upper value being more than twice that of any previously reported graphite-based foams.

Mechanochemical remediation of the chlorinated compounds contaminated soil depending on the minerals inside-the most reasonable approach

This study explored a possible destruction of hexachlorobenzene (HCB) as example of persistent organic pollutants (POPs) as well as the dechlorination mechanism by directly using minerals in the soil, such as antigorite, talc and olivine. Compared with a stable quartz phase of SiO2, all three Mg silicate minerals demonstrated certain degrading capacity for HCB with different efficiency order as: antigorite > talc > olivine > SiO2 at 2 h of milling time. Interestingly, olivine exhibited a better performance than antigorite at 4 h of milling time, giving destruction percentage of 92.7% over 89.0% even at high concentrated HCB up to 5% added. Raman and ESR characterizations of the ball milled sample with olivine indicated the formation of amorphous carbon and graphitic carbon, and the occurrence of free radicals was observed to play an important role in dechlorination and carbonization of HCB. The first identified effectiveness of directly using Mg silicate minerals, allowed no addition of active chemicals during the ball milling, therefore avoided the concern over extrinsic contaminations on the soil. Olivine was further utilized to deal with actual contaminated soil and showed unique advantages on application prospects.

Theoretical Study of Two‐Dimensional ZrO2/g‐C3N4 Sandwich Structure Loaded Noble‐Metal Rh Single‐Atom Catalysts

AbstractHydrogen production by photocatalysis will be an important means of obtaining hydrogen energy in the future. In this paper, a novel single‐atom catalysts structure was designed to improve the conversion efficiency of the reaction. A novel single‐atom catalysts was designed by using two‐dimensional crystalline and amorphous ZrO2 and Graphitic Carbon Nitride g‐C3N4 to form a sandwich single‐atom structure. Rh single‐atoms load was carried on the interlayer ZrO2 surface. The electronic structure and catalytic performance of the catalyst were calculated and analyzed by density functional theory. It has been shown that the electron concentration induced by the unsaturated coordination bond on the surface of the amorphous state has an excellent effect on the photocatalytic hydrogen evolution reaction. The local surface plasmon resonance effect of noble metal reduces the work function of catalyst and improves the electron transition ability. This paper proves that amorphous interlayer photocatalyst has a wide research prospect. It provides new ideas for the design of new catalysts and green energy in the future.

Enhancement of the mechanical and thermal transport properties of carbon nanotube yarns by boundary structure modulation

Carbon nanotubes (CNTs) exhibit extremely high nanoscopic thermal/electrical transport and mechanical properties. However, the macroscopic properties of assembled CNTs are significantly lower than those of CNTs because of the boundary structure between the CNTs. Therefore, it is crucial to understand the relationship between the nanoscopic boundary structure in CNTs and the macroscopic properties of the assembled CNTs. Previous studies have shown that the nanoscopic phonon transport and macroscopic thermal transport in CNTs are improved by Joule annealing because of the improved boundary Van-der-Waals interactions between CNTs via the graphitization of amorphous carbon. In this study, we investigate the mechanical strength and thermal/electrical transport properties of CNT yarns with and without Joule annealing at various temperatures, analyzing the phenomena occurring at the boundaries of CNTs. The obtained experimental and theoretical results connect the nanoscopic boundary interaction of CNTs in CNT yarns and the macroscopic mechanical and transport properties of CNT yarns.

Application of araçá fruit husks (Psidium cattleianum) in the preparation of activated carbon with FeCl3 for atrazine herbicide adsorption

The residual husks of the edible fruits of Psidium cattleianum were carbonized with FeCl3 as an activating agent and used as an adsorbent to remove the toxic herbicide. After the carbonization step, changes in the material’s structure were found. Activated carbon showed characteristics of microporous materials with a pore volume of 0.280 cm3 g−1 and surface area of 431 m2 g−1. Micrographs revealed the emergence of new cavities with a uniform and circular shape. The FTIR spectra showed the disappearance of some bands, remaining bands belonging to functional groups containing carbon, oxygen, and hydrogen. The XRD patterns confirmed the amorphous structure of the material even after the carbonization step, composed of amorphous graphitic carbon. EDS analysis showed that the carbon percentage increased and the oxygen decreased after the carbonization. The experiments were performed at neutral pH using 1 g L−1 of adsorbent. In equilibrium isotherms, the temperature played a considerable role in the adsorption capacity, increasing from 26.39 mg g−1 to 35.67 mg g−1 when the temperature varied from 298 to 328 K. The Liu isotherms were the ones that best fit the isotherm data. The changes in the adsorption enthalpy were endothermic (ΔH° 129.5 kJ mol−1). The general order kinetic model was the most adequate for kinetic data, presenting the lowest values of the Bayesian Information Criterion. Thus, activated carbon developed from the residues of the “araça” fruit showed promise in removing atrazine from aqueous solutions, with the great advantage of its high efficiency under neutral pH solutions and mild temperatures.

Promotional effects of defects on Ni/HAP catalyst for carbon resistance and durability during dry reforming of methane

Excellent carbon resistance and stable operations are essential for the industrialization of catalytic dry reforming of methane (DRM). In this study, a series of Ni/HAP and Ni/HAP-D catalysts are used to investigate their DRM reaction performance, including activity, durability, and resistance to carbon deposition. Combined with H2-TPR and XPS results, Ni in the Ni/HAP prefers to replace the external Ca atoms in hydroxyapatite. The inherently “Ca-deficient” HAP-D support facilitates a more robust anchor positioning for the Ni metal, and a significant fraction of the Ni atoms will be embedded in the inner structure of hydroxyapatite in the form of Ni2+[I] and Ni2+[II]. The catalytic activity of the Ni/HAP-D series of catalysts for CH4 and CO2 is significantly higher than that of the Ni/HAP series of catalysts, demonstrating that the Ni morphology, the combined form between Ni and support plays a crucial role in the DRM reaction. The deactivation rate of the Ni0.5/HAP-D catalyst is only 0.008% h−1 and 0.007% h−1 for CH4 and CO2, respectively, in a 200-h durability test. In the spent Ni0.5/HAP catalyst after 118-h reaction, the presence of NiO crystalline phase is detected, indicating that partial Ni is oxidized by CO2 during the reaction, and amorphous carbon and graphitic carbon are also detected. In contrast, no NiO crystalline phase is detected in the spent Ni/HAP-D catalyst after 200-h reaction, and only trace amounts of graphitic carbon are observed, indicating that the Ni presence pattern of Ni0.5/HAP-D contributes to its stability and resistance to carbon deposition. This work provides insights into the design of supported nickel-based catalysts with both excellent stability and surprisingly resistant to carbon deposits for DRM applications.

Frustrated Lewis Pairs Constructed on 2D Amorphous Carbon Nitride for High‐Selective Photocatalytic CO2 Reduction to CH4

Photocatalytic reduction of CO2 into high value‐added fuels paves a new avenue for alleviating the energy crisis and green‐house effect, yet it is still challenging to achieve a highly active photocatalyst with high selectivity. Herein, for the first time, a facile structural engineering strategy is developed to construct tunable frustrated Lewis pairs (FLPs) on 2D amorphous graphitic carbon nitride (C3N4) via the introduction of boric acid with the assistance of supercritical CO2, wherein the FLPs are composed of B(OH)2 groups (Lewis acid sites) and adjacent NHx (Lewis base sites). Ideally, the synergetic effects of the FLPs on the 2D amorphous C3N4 can help to efficiently adsorb, activate, and reduce CO2 to CH4 with enhanced selectivity of ≈96.0%.

Influence mechanism of Nano-Fe2O3 on amorphous carbon graphitisation in molecular view via ReaxFF MD simulation

ABSTRACT Nano-Fe2O3/C composites are widely used in the electrochemical energy storage field. Preparing nano-Fe2O3/C composites via graphitising the amorphous carbon inserting nano-Fe2O3 particles is potential if the influence mechanism of nano-Fe2O3 on the graphitisation of amorphous carbon is explored in-depth. Here, an amorphous carbon model (a-C model) and a nano-Fe2O3-inserting model (C\\Fe2O3 model) were built via the liquid-quench method, and the reaction of Fe2O3 and C during graphitisation was explored via the reactive force field (ReaxFF) simulation. The results showed that nano-Fe2O3 could inhibit the graphitisation of amorphous carbon, and the mechanism was revealed. The Fe2O3 molecules collided with the aromatic carbon layer because of the thermal motion, which caused the breaking of the carbon layer and the generation of CO2 and Fe. Certain Fe reduced from Fe2O3 destroyed the aromatic carbon layers by the strong affinity between Fe and C atoms and generated intercalation compounds (FeCx). Furthermore, the regularisation and stacking of large carbon layers were impeded. Thus, the graphitisation of amorphous carbon was inhibited.

Amorphous B-doped graphitic carbon nitride quantum dots with high photoluminescence quantum yield of near 90% and their sensitive detection of Fe2+/Cd2+

Graphitic carbon nitride quantum dots (CNQDs) are emerging as attractive photoluminescent (PL) materials with excellent application potential in fluorescence imaging and heavy-metal ion detection. However, three limitations, namely, low quantum yields (QYs), self-quenching, and excitation-dependent PL emission behaviors, severely impede the commercial applications of crystalline CNQDs. Here we address these three challenges by synthesizing boron-doped amorphous CNQDs via a hydrothermal process followed by the top-down cutting approach. Structural disorder endows the amorphous boron-doped CNQDs (B-CNQDs) with superior elastic strain performance over a wide range of pH values, thus effectively promoting mass transport and reducing exciton quenching. Boron as a dopant could fine-tune the electronic structure and emission properties of the PL material to achieve excitation-independent emission via the formation of uniform boron states. As a result, the amorphous B-CNQDs show unprecedented fluorescent stability (i.e., no obvious fading after two years) and a high QY of 87.4%; these values indicate that the quantum dots obtained are very promising fluorescent materials. Moreover, the B-CNQDs show bright-blue fluorescence under ultraviolet excitation when applied as ink on commercially available paper and are capable of the selective and sensitive detection of Fe2+ and Cd2+ in the parts-per-billion range. This work presents a novel avenue and scientific insights on amorphous carbon-based fluorescent materials for photoelectrical devices and sensors.

Constructing FeN4/graphitic nitrogen atomic interface for high-efficiency electrochemical CO2 reduction over a broad potential window

Summary Atomically dispersed Fe–N–C catalyst has shown great performance in the CO2-to-CO conversion, yet the high CO selectivity is achieved only within a rather narrow potential range, which cannot well meet the requirements for the following CO dimerization or hydrogenation. Here, we developed a hydrogen-pyrolysis etching strategy to precisely manipulate the uncoordinated N dopants in the Fe–N–C catalyst. This strategy could preferentially eliminate pyridinic and pyrrolic N atoms while leaving graphitic N. The resulting catalyst gave a CO faradaic efficiency (FECO) above 90% over a broad window from −0.3 to −0.8 V (versus RHE) (in particular, FECO > 97% at −0.6 V). In situ ATR-SEIRAS and first-principle calculations further revealed that this strategy can not only suppress the parasitic H2 generation but also promote CO2 activation and protonation with the assistance of co-adsorbed H2O on the “atomic interface” of “FeN4/graphitic N.”

Alumina Support for Cobalt Catalyst in a Methane Dry Reforming Reaction: The Role of Water Content in a Solvent Medium

This study aimed to synthesize alumina from an inorganic aluminum nitrate precursor in various binary solvent systems of ethanol and water using the sol-gel self-assembly (SSA) method, employing a triblock copolymer, pluronic P123, as the pore-directing agent. The resulting materials were implemented as a support for the cobalt (Co) catalyst in a methane dry reforming (MDR) reaction at 1073 K under 1 atm. Regardless of the water percentage used in the support synthesis, the methane dry reforming reaction over Co catalysts on alumina supports showed the negligible change in conversion during the 12 h reaction. Moreover, there was evidence of large quantities of amorphous carbon and graphitic carbon on the spent catalyst surface. However, the low oxidation temperature of these deposited carbons could help maintain the balance between the carbon formation and the carbon elimination processes on the catalyst surface during the reforming reaction, hence prolonging the lifetime of the catalyst. The high conversion of methane (CH4) from 64.6% to 82.8% and carbon dioxide (CO2) from 70.7% to 86.6% for the MDR reaction over the as-prepared alumina-supported Co catalyst demonstrated a significant improvement in catalyst production for the MDR reaction from the viewpoint of large-scale applications.

Coupling between structural properties and charge transport in nano-crystalline and amorphous graphitic carbon films, deposited by electron-beam evaporation

Nano-crystalline and amorphous films of graphitized carbon were deposited by electron-beam evaporation of bulk graphite. Structural properties and the size of graphite nanoclusters (L ≈ 1.2–5 nm) in the films were determined from the analysis of their Raman spectra. Electrical properties of the bulk nano-crystalline graphite reference sample and the deposited graphitic carbon films were measured by means of the Hall effect technique within the temperature range from 290 to 420 K. The electrical conductivity σ and Hall mobility μH of all samples exhibited exponential temperature dependences, indicating on the non-metallic behavior. Electrical properties of the amorphous graphitic carbon thin films, deposited at low substrate temperatures (620 and 750 K) were analyzed in the scope of the hopping charge transport mechanism via localized states. We have shown that the charge transport in the bulk and thin film (920 K) nano-crystalline graphite samples is carried out via the tunneling and thermionic emission over potential barriers at the grain boundaries.This paper contributes towards better understanding of coupling between structural and electrical properties of graphitic carbon thin films.