Carbon Atoms In Graphite Research Articles

Hydroxymethylfurfural adsorption modulating charge separation characteristics of carbon-rich carbon nitrides for simultaneous photocatalytic hydrogen evolution and 2,5-diformylfuran production

Carbon-rich melon-based carbon nitrides (CNs), in which the sp2 N atoms and the terminal C–NH2 within the heptazine rings are partially replaced by the graphitic carbon atoms and C–H terminals, respectively, are synthesized through the condensation of 2,4,6-triaminopyrimidine-added supramolecular complexes comprising melamine and cyanuric acid. Optical characterizations reveal that increasing the C/N ratio in CNs improves their light-harvesting and charge-separation capabilities. Nevertheless, the photocatalytic activities of carbon nitrides reach an optimal level at an appropriate C/N ratio for simultaneous H2 evolution and 2,5-diformylfuran (DFF) production from 5-(hydroxymethyl)furfural (HMF) aqueous solution. Hydrogen evolution from water and DFF production by selective HMF oxidation are driven by photogenerated electrons and holes, respectively. Density functional theory calculations suggest that the adsorption of HMF on carbon-CN dramatically influences the molecular orbital contributions to the lowest singlet excited state, altering its charge separation character and, consequently, the photocatalytic activity. The improvement of charge separation in the optimized CN by HMF adsorption is further confirmed by experimental measurements.

Using Activated Biochar from Caryocar brasiliense Pequi Almonds for Removing Methylene Blue Dye in an Aqueous Solution

Water pollution remains a global problem that urges researchers to develop new technologies aimed at environmental restoration. Here, this study aimed at obtaining an activated biochar from pequi almonds for dye removal. Before and after adsorption, the materials underwent characterization using techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Raman spectroscopy, and thermogravimetric analysis (TG). The biochar from the pequi almond was called BA, and the activated biochar from the pequi almond was called ABA. The influence of the pH, contact time, and adsorbate concentration on adsorption was investigated using the dye methylene blue. The morphological assessment revealed higher cracks and pores in the ABA than in the BA. The TG showed that the BA lost approximately 19% more mass than the ABA, indicating that activation occurred. The activation contributed to the decrease in the degree of disorder in the BA because of the increased number of graphitic carbon atoms (ordered) in the ABA, as observed via Raman. The adsorption kinetics followed a pseudo-second-order model, while the adsorption isotherms followed the Langmuir model. The BA adsorption capacity was 500.00 mg g−1, constituting a robust solution for dye removal from aqueous environments. Therefore, this implies the success of the process.

The influence of Compton electrons on the rearrangement of carbon atoms in graphite: new evidence from the analysis of 2D Raman band

The influence of Compton electrons on the rearrangement of carbon atoms in graphite: new evidence from the analysis of 2D Raman band

Defective Potassium Poly(Heptazine Imide) Preventing Spin Delocalization and Hole Transfer Deactivation for Efficient Solar Energy Conversion and Storage.

Anti-site defective potassium poly(heptazine imide) (KPHI) with the central nitrogen atoms partially replaced by graphitic carbon atoms in the flawed heptazine rings is prepared by direct ionothermal treatment of the rationally designed supramolecular complex in KSCN salt molten. Compared to the KPHIs without the anti-site defect, the anti-site defective KPHI demonstrates significantly improved photocatalytic and dark photocatalytic performances for H2 evolution reaction (HER). In the presence of the hole scavenger, the anti-site defective KPHI exhibits superior photocatalytic stability for HER lasting 20h, whereas the deactivation is observed from the ordinary KHPIs after 3h HER. Moreover, the H2 yield in the dark by the stored photoelectrons in the anti-site defective KPHI increases by more than an order of magnitude. Density functional theory calculations reveal that the anti-site defective unit in KPHI not only prevents spin delocalization but also inhibits the deactivation of hole transfer, which are beneficial to photoelectron storage and photocatalytic activity. The findings in this study provide insight into the photophysical and catalytic properties of KPHI, which conclude a strategy to improve the performances for solar energy conversion and storage by incorporating intrinsic anti-site defects in KPHI.

Investigating the effect of graphite pretreatment and contribution of the oxidizer in the synthesis of graphite oxide by hummers approach

Graphite oxide (GrO), the precursor of graphene oxide (GO) has been prepared by pre-treating graphite in a mixture of nitric and sulfuric acid, followed by chemical oxidation by a modified Hummers approach. The effect of pretreatment, KMnO4, and sulfuric acid on the chemical oxidation reaction was observed by characterizing GrO specimens on the bulk scale. KMnO4 oxidizes the carbon atoms by withdrawing electrons, instead of penetrating between the stacked carbon layers and directly interacting with the carbon atoms. Sulfuric acid and water molecules penetrate the interlayers of carbon planes and form the functionalities by nucleophilic attack on the charged carbon atoms. The pretreatment of graphite induces a small number of moieties, distributed evenly across the entire domain, serving as the primary reaction site of chemical oxidation. The inclusion of a small amount of functionalities marginally increases the lattice spacing and mildly intercalates the stacked carbon layers, facilitating the diffusion of acid and water molecules in the later step. The prepared GrO possesses only 24% graphitic carbon atoms and 11-layer of carbon stacking, confirming significant oxidation and intercalation.

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.”

Infrared Spectroscopy of Ultraviolet-Irradiated Carbon Nanotubes

The possibility of using the UV irradiation for a functionalization of carbon nanotubes with different degrees of structural perfection is considered. In investigations, the method of infrared spectroscopy is used. A change in the number of functional groups under the short-term UV irradiation of specimens with multiwall carbon nanotubes is estimated by a change in the relative intensity of the IR spectral bands corresponding to vibrations of the functional groups in comparison with the relative intensity of the band corresponding to vibrations of the carbon atoms in graphite.

Preparation of Mo2C–carbon nanomaterials for hydrogen evolution reaction

Highly active, stable and low-cost noble metal-free electrocatalysts are essential for production of hydrogen. However, preparation of such catalysts is still highly challenging so far. In this work, the Mo2C–carbon nanomaterials have been prepared by controlled thermal technique. By controlling concentration of the reactants in the experimental condition, the Mo2C–carbon nanomaterials have been fabricated, which leads to decreases in contact resistance b/w Mo2C–carbon nanomaterials and graphitic carbon atoms. As a result, the Mo2C–carbon nanomaterial electrode shows remarkable activity for hydrogen evolution reactions with a small onset overpotential of 95 mV, a Tafel slope of 62 mV dec−1, an high exchange current density of 0.32 mA cm−2, good stability during long-term 1000 cycles and exhibits long-term durability for several days. This study opens a new method for the preparation of highly active non-noble electrode for production of hydrogen from water splitting.

Enhancement of Electrical Property of Thermally-Annealed Nano Carbon Based Polymer Composite By High Frequency Induction Heating

It has been said that CNT and Graphene have especially excellent electrical, thermally and mechanical property. Also it has been expected as fillers for polymer composite instead of conventional carbon fiber. Recently large amount of research has been done about Nanocarbon, so we can get easily a lot of kind of Nanocarbon. There is not the universal standard for Nanocarbon materials especially CNT and Graphene. Therefore, it causes a large problem for prediction of property of composites that their qualities and size are not uniform because property and structure of CNTs are changed by production method. CNTs has different names and property depending on the number of layers such as Single-wall carbon nanotube (SWCNT) and Multi-wall carbon nanotube (MWCNT). So the purpose in this study is to clarify the effect of Nano carbon materials quality on the properties of polymer based Nanocarbon composite and to develop polymer matrix Nanocarbon composite which have excellent properties. We improve the quality by heating the Nanocarbon materials in the inert atmosphere by high frequency induction heating. Also we compared filler properties of Nanocarbon composite polymer. First, the sample of CNT and Graphite was set into a carbon crucible and heated in the inert atmosphere for 10 to 30 minutes by high frequency induction heating. Thereafter, the qualities of the annealed samples were analyzed by Raman spectroscopy. In Raman spectroscopy can analyze crystal integrity, diameter and other. In the Raman scattering spectrum of CNT appear characteristic waveforms. Specifically, it are appeared near 1590 cm⁻¹ called G band and near 1350 cm⁻¹ called D band. Since the G band is derived from the in-plane stretching motion of the 6-membered ring structure of carbon atoms in graphite and the D band is derived from its defect structure, the crystal integrity (G / D ratio) is determined by the ratio of the peaks of the G band and the D band . In general, the larger the G / D ratio is, the higher the crystalline perfection is. For example, when graphene is thermally annealed at 1500 ° C for 15 minutes, the Full Width at Half Maximum (FWHM) is larger than that of without thermally annealing. It showed that impurities in graphite were removed by thermal annealing. But, there was not large change in G/D ratio. Second, the shapes of samples were analyzed for example diameter and length by using a scanning electron microscope. In SEM observation, the shape and size of Nanocarbon was mainly observed. TEM mainly observed the diameter, size and layers of CNT. Next, the nanocarbon samples were mechanical mixing with the polymer. This matrix used polypropylene (PP).The mixer used was of an elliptical blade. The temperature was 200 to 250 ° C. for 30 to 60 minutes, and the rotation speed was 80 to 100 rpm. Finally, the volume resistivity of the prepared composite material was measured using a resistivity meter. In general, the volume resistivity of PP is about 10 ^ 16 to 10 ^ 17 Ωcm, and the boundary through which electricity passes is said to be 10 ^ 6 Ωcm. Also, we think that annealed high quality Nanocarbon property in comparison with no thermal annealed Nanocarbon. So, we will be able to improve property of Nanocarbon composite.

Fluorination of nuclear graphite IG-110 in molten 2LiF-BeF2 (FLiBe) salt at 700 ºC

It is important for the development of advanced nuclear reactors to understand if the exposure to molten fluoride salts changes physical properties of graphite and its ability to absorb tritium. This paper demonstrated that the interaction between high purity nuclear grade graphite IG-110 and molten salt mixture 2LiF-BeF2 (FLiBe) at 700 °C for twelve hours in argon envirnoment resulted in graphite fluorination and changes in graphite microstructure. XPS C1s spectra analysis shows an increase in F functionalization (from 3.5% to 9.0–19.3%), an increase in the sp3/sp2 ratio (from 0.1496 to 0.1798), and F1s spectrum analysis confirms appearance of CF bonds. Raman spectra show an increase in ID/IG ratio from 0.35 to 0.69 and an appearance of peak shoulders characteristic of CF bond formation. GDMS depth analysis from the surface to 5 μm depth shows a higher depth penetration of F compared to that of Li and Be, indicative of surface salt reduction and bulk graphite fluorination. FLiBe reduction by graphite fluorination is not thermodynamically favorable, but certain carbon sites in the graphite are more reactive than the majority of carbon atoms in graphite. We argue that graphite fluorination occurred at these reactive sites, leading to the reduction of salt at the graphite surface. XRD and Raman confirmed microstructural changes. This indicates that the fluorination process may introduce new active sites as existing active sites are consumed, which could be advantageous for tritium chemisorption from FLiBe.

Hexagonal rotator order of bound ionic surfactants and temperature triggered dispersion of carbon nanotubes

Oxidized Carbon Nanotubes (CNT) form stable adducts with ammonium ions exhibiting long alkyl chains. Outer surfaces of CNT adducts are completely covered by hydrocarbon tails, which spontaneously organize in hexagonal rotator order, with 1 hydrocarbon tail per 8 graphitic carbon atoms of the external CNT wall. Order-disorder transitions, which involve loss of packing and of zig-zag planar conformation of the bound hydrocarbon tails, occur by heating at temperatures not far from room temperature and lead to temperature-triggered dispersion in organic media of the CNT adducts. CNT adduct formation is reversible with pH changes, as clearly shown by reversible moving of CNT between apolar and polar immiscible phases.

An improved model for N2 adsorption on graphitic adsorbents and graphitized thermal carbon black—The importance of the anisotropy of graphene

Computer simulations of N2 adsorption on graphite frequently use the 10-4-3 equation with Steele’s molecular parameters to describe the dispersive-repulsive interaction between a molecule and graphite. This model assumes that graphite is a uniformly homogeneous continuum solid, and its derivation implies the following assumptions: (1) the solid is built from stacked, equally spaced graphene layers, (2) there is an infinite number of layers, and (3) the carbon atom molecular parameters are invariant for all layers (collision diameter of 0.34 nm and reduced well depth of interaction energy of 28 K). Despite the fact that this model can give an acceptable description of experimental data for this system, there are experimental observations that simulation results fail to account for. First, the isotherm does not exhibit a step in the sub-monolayer coverage region at 77 K, which is attributed to a transition from the supercritical state of the adsorbate to the commensurate state, and therefore fails to reproduce the cusp and heat spike in the experimental isosteric heat curve versus loading at close to monolayer coverage. Second, the simulation results overpredict the experimental data in the multilayer region. These discrepancies suggest that (1) the absence of lateral corrugation in the 10-4-3 potential misses the commensurate to incommensurate transition and (2) the long-range solid-fluid potential, experienced by the second and higher layers onwards, is too strong. Here we examine a revised graphite potential model that incorporates three features absent from the 10-4-3 model: (1) an energetic corrugation of the potential arising from the discrete atom structure of the adsorbent, (2) the unequal spacing of the graphene layers due to the anisotropic force field acting on graphene layers at the surface, and (3) the different polarizabilities of carbon atoms in graphite, parallel and normal to the graphene surface. These features are corroborated by a number of experimental measurements and quantum-mechanical calculations: (1) the Low-Energy Electron Diffraction (LEED) and Surface-Extended X-ray Absorption Fine Structure (SEXAFS) experiments show that the first adsorbate layer is smaller than predicted by the 10-4-3 model with the traditional molecular parameters suggested by Steele, and (2) the potential well depth for atoms in graphene is stronger than for C-atoms in graphite. The simulation results using this revised graphite model give an improved description of the fine features of adsorption of N2 on graphite: the sub-step in the first layer of the isotherm, the spike in the isosteric heat curve versus loading, and the coverage at higher loadings.

On the effect of carbon content for achieving a high performing Na3V2(PO4)3/C nanocomposite as cathode for sodium-ion batteries

An in-situ generated carbon matrix has demonstrated to be essential to provide electrical conducting properties to Na3V2(PO4)3 as cathode materials for sodium-ion cells. Na3V2(PO4)3/C nanocomposites are synthesized by varying their eventual carbon content in order to determine the influence in the electrochemical behavior. X-ray diffraction patterns evidence the crystallinity and purity of Na3V2(PO4)3, while Raman spectroscopy reveals the disordered character of the carbon phase. The determination of the chemical state of the carbonaceous phase unveils that an increase of the carbon content involves a decrease of carboxyl groups and a slight increase of graphitic carbon atoms, in agreement with the Raman results. The electrochemical characterization of these composites in sodium half cells reveals that carbon contents close to 7% are preferred to provide cycling stability, while the best rate performance is achieved for the sample with carbon content close to 11%. A full sodium-ion cell delivers an energy density of 320Whkg−1 at 2C.

Density functional theory investigation of oxygen interaction with boron-doped graphite

Boron inserted as impurity by substitution of carbon atoms in graphite is known to change (improve or deteriorate) oxidation resistance of nuclear graphite, but the reason for both catalytic and inhibiting oxidation is still uncertain. As a first step, this work is more specially devoted to the adsorption and diffusion of oxygen atoms on the surface and related to the problem of oxygen retention on the pure and boron-containing graphite surfaces. Adsorption energies and energy barriers associated to the diffusion for molecular oxygen recombination are calculated in the density functional theory framework. The existence of boron modifies the electronic structure of the surface, which results in an increase of the adsorption energy for O. However, low boron loading makes it easier for the recombination into molecular oxygen. For high boron concentration, it induces a better O retention capability in graphite because the presence of B-B bonds decreases recombination of the adsorbed oxygen atoms. A possible explanation for both catalytic and inhibiting effects of boron in graphite is proposed.

Synthesis of Carbon Nanofibers from Carbon Foam Composites via Oxyacetylene Torch Ablation

Carbon nanofibers were in-situ synthesized on porous carbon composites via a simple and economic technique of oxyacetylene torch ablation without catalyst assistance. The resultant nanofibers with good crystallinity in the (002) plane were polycrystalline graphite, which grew in the ablation center region. They were generally tens of nanometers in diameter, several microns in length, and grew at different orientations, exhibiting flower-like nanofiber clusters covered with amorphous carbon film. The formation mechanism may be governed by exfoliation of graphite layers, or attachment of graphitic carbon atoms to silicon monoxide for growth during the cooling process.

Sulfur-Doped Graphene Supported Platinum Electrocatalysts for Oxygen Reduction Reaction in PEM Fuel Cells

Polymer electrolyte membrane (PEM) fuel cells have been viewed as promising power source candidates for transport, stationary, and portable applications due to their high efficiency and low emissions. The platinum is the most commonly used catalyst material for the oxygen reduction reaction (ORR) at the cathode of PEM fuel cells; however, despite ample investigations being done on this type of catalyst, the performance and durability of platinum still need to be improved in order to meet the commercial target. The material on which the catalyst is supported is important for the high dispersion and narrow distribution of Pt nanoparticles, and these characteristics are closely related to electrocatalytic activity of the catalysts. The support materials can influence the catalytic activity by interplaying with catalytic metals, and the durability of the catalyst is also greatly dependent on its supports.Graphene has recently emerged as a highly promising catalyst support material for PEMFC applications owing to its immense surface areas, along with excellent conductivity and electron transfer capabilities that are important criteria pertaining to electro-catalysis. Graphene is theoretically composed of only graphitic carbon atoms which can provide added resilience against carbon corrosion during PEMFC operation, although the relatively inert and hydrophobic nature of its surface does not culminate in facile Pt deposition, requiring functionalization procedures to obtain well dispersed nanoparticles and overcome stability limitations. To this end, nitrogen doped graphene and other graphitic carbons have been extensively developed and investigated for fuel cell catalyst applications, either as stand-alone ORR electrocatalysts in alkaline media as Pt nanoparticle supports under acidic (i.e. PEMFC) conditions. The presence of nitrogen dopants has been reported to exert a “tethering” effect on Pt nanoparticles, providing both beneficial catalyst activity and stability enhancements. While density functional theory simulations exist in the literature investigating the adsorption and binding interactions between Pt and either nitrogen and boron doped graphene or carbon nanotubes (CNTs), there exists an overall lack of fundamental understanding regarding the Pt-heteroatom doped graphene catalyst-support interactions and their associated impact on ORR performance and operational stability. Furthermore, the impact of graphene doped with various other heteroatoms (i.e. sulfur) remains largely unexplored despite their high potential for applications as ORR catalysts or catalyst support materials. Elucidation of these important considerations can be provided by effectively linking fundamental computational simulations with detailed experimental investigations.In the present work, we report the development of sulfur-doped graphene (SG) by thermal shock/quench annealing a mixture of graphene oxide (GO) and phenyl disulfide (PDS). These materials were used as Pt nanoparticle support materials, whereby after Pt deposition onto SG (Pt/SG) by a modified ethylene glycol (EG) method, uniformly sized nanoparticles well dispersed across the entirety of the SG surface were successfully obtained. Improved ORR activity was found for Pt/SG in comparison to Pt supported on un-doped graphene (Pt/G) along with commercial state of the art Pt/C (Figure 1). Furthermore and most notably, we also observed significantly enhanced stability of Pt/SG (Figure 1).On the basis of these observations, we performed ab initio density functional theory calculations to investigate the interactions occurring between SG and Pt and elucidate the root causes of ORR performance and stability enhancements. We found that the strengthened interaction and binding energies between Pt and SG arose, and could exclusively be linked to sulfur incorporation based on comparative investigations with un-doped G. Specifically, sulfur doping led to stronger adsorptive and cohesive binding energies with Pt, leading to the aforementioned catalyst-support tethering effect, along with negatively shifting the d-band center of the Pt atoms. These findings were used to explain the dramatically enhanced stability and improved activity of Pt/SG, respectively, in comparison to both Pt/G and Pt/C. This work represents the first comprehensive report of fundamental ab initio simulations linked to rigorous experimental investigations for sulfur doped graphene, and furthermore Pt/SG is presented for the first time as a highly active ORR catalyst with exemplary stability for PEMFC applications.

Melting of Hexane Monolayers Adsorbed on Graphite: The Role of Domains and Defect Formation

We present the first large-scale molecular dynamics simulations of hexane on graphite that completely reproduce all experimental features of the melting transition. The canonical ensemble simulations required and used the most realistic model of the system: (i) a fully atomistic representation of hexane; (ii) an explicit site-by-site interaction with carbon atoms in graphite; (iii) the CHARMM force field with carefully chosen adjustable parameters of nonbonded interaction, and (iv) numerous >or=100 ns runs, requiring a total computation time of ca. 10 CPU years. The exhaustive studies have allowed us to determine the mechanism of the transition: proliferation of small domains through molecular reorientation within lamellae and without perturbation of the overall adsorbed film structure. At temperatures greater than that of melting, the system exhibits dynamically reorienting domains whose orientations reflect the graphite substrate's symmetry and whose size decrease with increasing temperature.

Fabrication of partially graphitic three-dimensional nitrogen-doped mesoporous carbon using polyaniline nanocomposite through nanotemplating method

A novel nitrogen-doped mesoporous carbon with three-dimensional (3D) body centered Ia 3 ¯ d structure (N-MCK6) has been successfully prepared for the first time by employing KIT-6 mesoporous silica as a hard template with aniline molecule as a carbon precursor. The polymerization of aniline molecules inside the mesochannels of KIT-6 template has been performed by ammonium peroxydisulfate. The obtained material has been unambiguously characterized by powder X-ray diffraction, nitrogen adsorption at −196 °C, high resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and X-ray photoelectron spectroscopy (XPS). XRD analysis revealed that N-MCK6 possesses 3D cubic structure with an enatiomeric pair of independently interpenetrating 3D continuous networks of mesoporous channels that are mutually intertwined and separated by carbon walls. HRTEM images of N-MCK6 display highly ordered mesoporous structure with linear array of mesopores, which are arranged in regular intervals. It has been found that the material is partially graphitic and possesses high surface area, pore volume and uniform pore size distribution. XPS, CHN and EELS analysis confirm that the nitrogen atom can be successfully doped in the carbon nanostructure. XPS results also revealed that the sample mainly possesses graphitic carbon atoms which are bonded to nitrogen in the form of imine and amine groups. This simple method can offer material with a considerable amount of nitrogen in the carbon lattice, which can be applied for many electrical and electronic, and energy storage applications.

Adsorption, diffusion, and recombination of hydrogen on pure and boron-doped graphite surfaces

Boron inserted as impurity by substitution of carbon atoms in graphite is known to modify the reactivity of the surface in interaction with hydrogen. Boron induces a better H retention capability in graphite while it makes easier the recombination into molecular hydrogen under heating in thermal-desorption experimental conditions. It has already been calculated that boron modifies the electronic structure of the surface, which results in an increase of the adsorption energy for H. This result seems in good agreement with the better retention for H in doped graphite, but contradictory with the easier recombination observed. The aim of this work is to dismiss this contradiction by elucidating the modifications induced by boron in the recombination mechanism. We studied the diffusion of H on pure and boron-doped graphite in the density functional theory framework. We determined a diffusionlike mechanism leading to molecular hydrogen formation. Finally, we have shown the fundamental modifications induced by boron on the [0001] graphite surface reactivity. From these calculations it stands out that recombination is the result of desorption on pure graphite and diffusion on B-doped surfaces, while the activation energy for the rate limiting step is half reduced by boron. The results are compared to experimental observations. The connection between the cluster and periodic quantum modes for graphite is also discussed.

Thermally activated electron emission from nano-tips of amorphous diamond and carbon nano-tubes

The sp 2 character of graphite can carry electricity like a metal and the sp 3 character of diamond can emit electrons in vacuum like an insulator. In this research, we have studied two ways of combining the electrical conductance and electron emission properties in carbon materials. In one case, the two characters are mingled atomistically to form a rather uniform mixture of amorphous diamond. Alternatively, graphite basal planes are wrapped around to form nano-tubes that exhibit a slight diamond character. Both amorphous diamond and carbon nano-tubes (CNTs) contain emission tips of nanometer sizes. When they are connected to a negative bias, they can emit electrons in vacuum toward an anode at very low turn-on field. However, when the cathode material is heated up, the responses of electron emission in vacuum are dramatically different between the two types of carbon materials. At a temperature of 300 °C, amorphous diamond can emit 13 times more electrons than it did at room temperature; but CNTs show no response to thermal agitation. The thermally sensitive emission of amorphous diamond indicated that electrons climbed up an energy ladder to reach the vacuum level for efficient emission. The energy ladder contained minute but discrete energy levels that were created by distorting the tetrahedral bonds of carbon atoms to different degrees. On the other hand, the CNTs are substantially graphitic so the energy gap between their conduction band and valence band overlap and are continuous in energy. In this case, electrons could not acquire energy to reach the vacuum energy unless the temperature could be sufficiently high. Hence, it confirms that CNTs emit electrons primarily by enhancing the applied field on nano-tips. This is in contrast to amorphous diamond that emits electrons by combining graphitic carbon atoms and diamond-like carbon atoms of various states.