Graphite Lattice Research Articles

Preparation of needle coke from low-temperature coal tar pitch based on modification, component separation and component blending

Needle coke is widely used in the production of ultra-high power electrodes, special carbon materials, carbon fibers, and their composites. How to prepare needle coke with excellent performance through directional adjusting of raw material components is a hot research topic. In this paper, coal tar pitch (CTP) was extracted from low-temperature coal tar (Low-coal tar). To further increase the content of quinoline-soluble, CTP was modified by formaldehyde via chemical polymerization. By adjusting the blending ratio of hexane-insoluble toluene-soluble (HI-TS) and toluene-insoluble tetrahydrofuran-soluble (TI-AS) obtained by modified coal tar pitch (HCTP) separation adopting solvent extraction, a series of green needle coke and needle coke were prepared. The physicochemical structures were analyzed using FTIR, TG, Py-GC/MS, XRD, PM, and SEM, and the electrochemical properties were evaluated and analyzed. The results show that the Lc and La of green needle coke and needle coke firstly increase and then decrease with the decrease of TI-AS content, while the ID/IG demonstrated the opposite tendency. When the content of TI-AS is 16.67%, it is favorable to improve the micro-morphology of needle coke and increase the content of the ideal graphite lattice (from 24.47% to 31.88%) and needle coke yield (44.03%). In this paper, the composition distribution of CTP was adjusted, and the effect of the blending ratio of HI-TS and TI-AS on the structure of green needle coke and needle coke was investigated, improving the added value of Low-coal tar and providing data reference for the directional regulation of needle coke.

Adsorption behavior of graphite‐like walnut shell biochar modified with ammonia for ciprofloxacin in aqueous solution

AbstractBACKGROUNDGraphite‐like biochar of NWSC600K was prepared at 900 °C using walnut shell as the raw material and aqueous ammonia (NH3·H2O) as an activator, and characterized using transmission and scanning eletron microscopy (TEM, SEM), X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Raman spectroscopy and Fourier transform infrared (FTIR). The study investigated the adsorption performance and mechanism of NWSC600K for ciprofloxacin (CIP).RESULTSThe results showed that extremely tiny pores were found on the surface of NWSC600K, which increased its specific surface area to 823.91 m2 g−1, whereas the average pore size of NWSC600K decreased to 3.23 nm. The results of TEM, XRD and Raman spectroscopy detected well‐arranged lattice stripes as well as characteristic peaks corresponding to the graphite lattice appearing on the surface of NWSC600K. Moreover, the ID/IG value for NWSC600K was 1.429. The FTIR results showed that functional groups including the amino group were formed on NWSC600K.CONCLUSIONThe adsorption capacity of NWSC600K for CIP was 158.14 mg g−1 and the corresponding removal rate was 97.5% at pH 7. The pH value impact on the removal efficiency of CIP greatly, and the removal rate of CIP decreased linearly with increasing pH. The coexisting ions also would inhibit the adsorption of CIP on NWSC600K. Results obtained from kinetic and isotherm models, thermodynamics and characterization analyses suggested that pore‐filling, π–π stacking, hydrogen bonding, hydrophobicity and electrostatic interaction existed during the adsorption process. The adsorption was a nonspontaneous exothermic reaction. © 2024 Society of Chemical Industry (SCI).

Reverse degree-based topological indices study of molecular structure in triangular ϒ-graphyne and triangular ϒ-graphyne chain

Topological indices are mathematical descriptors of the structure of a molecule that can be used to predict its properties. They are derived from the graph theory, which describes the topology of a molecule and its connectivity. The main objective is mathematical modeling and topological properties of ϒ-graphyne. Current research focuses on two structures made from hexagonal honeycomb graphite lattices named triangular ϒ-graphyne and triangular ϒ-graphyne chains. The authors have simultaneously computed the first and second Reverse Zagreb indices, reverse hyper-Zagreb indices, and their polynomials. This research also derives mathematical closed-form formulas for some of its fundamental degree-based molecular descriptors. Researchers have been trying to synthesize a novel carbon form called Graphyne. For over a decade but with no success. Recently, some researchers have made a breakthrough in generating Carbons elusive allotrope and solved a long-standing problem in carbon materials. This wonder material is created to rival the conductivity of graphene but with control. These results opened new ways of research in the fields of semiconductors, electronics and optics. Furthermore, graphical and tabular results will help to investigate the structure-property relationships in γ-graphyne.

Modifying Polymer-Based Hard Carbons for Enhanced Understanding of Sodium Storage Properties

Numerous theories on the storage of sodium in hard carbons can be found in the literature. In particular, understanding the contributions of (heteroatom) doping, porosity and graphitic layers is of great importance. Much of the current literature on hard carbons uses different biomaterials as precursors in order to improve the sustainability of the synthesis. However, large differences in the composition of the starting materials and the presence of foreign atoms make a systematic investigation of the storage process extremely difficult.Therefore, a hard carbon material based on furan resins was used in this work to obtain a well-defined starting material that can be modified systematically. This allows a detailed investigation of the effects caused by those modifications. Modifications can be achieved by directly adding various template materials to the polymerization process. Both doping with heteroatoms by adding template chemicals such as boric acid and the introduction of graphitic layers by adding high-purity graphite during polymerization were investigated.Addition of boron and phosphorus heteroatoms led to an increase in reversible capacity up to 240 mAh g-1 from 150 mAh g-1 for carbonization temperatures as low as 650°C. Formation of a potential plateau was observed for boron doping, which is usually found at higher carbonization temperature surpassing 1000°C. Utilizing Raman and XRD spectroscopy, crystallite size was found to be decreasing with phosphorus doping, while boron doping led to an increase. This increase could be a possible explanation for the observed capacity plateau.The addition of high-purity carbon samples, such as KS6L graphite or graphene, allowed for a targeted introduction of single- and multi-layer graphitic domains without alteration of additional properties. Increasing graphite content up to 5 wt-% during polymerization resulted in enhanced electrochemical characteristics, including increased sodium intercalation into the lattice and shift of the sloping proportion to lower potentials. Further increase up to 10 wt-% led to a vanishing of the plateau potential and a lowering of the reversible capacity. The results indicate that the interlayer spacings has now decreased below a threshold, which prohibits the sodium from intercalation between the graphitic layers. Additionally, doping Hard Carbons with graphene revealed a capacity decrease at content ratios as low as 2 wt-%, emphasizing the significance of both the stacking and interlayer spacing of the graphitic lattice, as well as the chemical composition, for efficient sodium storage.In summary the results presented provide an enhanced understanding into the sodium storage properties of Hard Carbons, which help improve the design of synthesis processes for more cost-efficient and high-performance carbon materials. Figure 1

Induced charges in a Thomas–Fermi metal: insights from molecular simulations

We study the charge induced in a Thomas–Fermi metal by an ion in vacuum, using an atomistic description employed in constant-potential molecular dynamics simulations, and compare the results with the predictions from continuum electrostatics. Specifically, we investigate the effects of the Thomas–Fermi screening length l TF and the position d of the ion with respect to the surface on the induced charge distribution in a graphite electrode. The continuum predictions capture most of the features observed with the atomistic description (except the oscillations due to the atomic sites of the graphite lattice), provided that d and l TF are larger than the inter-atomic distances within the electrode. At large radial distance from the ion, the finite l TF case can be well approximated by the solution for a perfect metal using an effective distance d + l TF . This requires a careful definition of the effective interface between the metal and vacuum for the continuum description. Our atomistic results support in particular an early analytical prediction (Vorotyntsev and Kornyshev, Sov. J. Exp. Theor. Phys. 51, 509 (Mar., 1980)) for a single charge at the interface between a Thomas–Fermi metal and a polarisable medium, which remains to be tested in atomistic simulations with an explicit solvent.

Impacts of Fuel Stage Ratio on the Morphological and Nanostructural Characteristics of Soot Emissions from a Twin Annular Premixing Swirler Combustor.

Soot particles emitted from aircraft engines constitute a major anthropogenic source of pollution in the vicinity of airports and at cruising altitudes. This emission poses a significant threat to human health and may alter the global climate. Understanding the characteristics of soot particles, particularly those generated from Twin Annular Premixing Swirler (TAPS) combustors, a mainstream combustor in civil aviation engines, is crucial for aviation environmental protection. In this study, a comprehensive characterization of soot particles emitted from TAPS combustors was conducted using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The morphology and nanostructure of soot particles were examined across three distinct fuel stage ratios (FSR), at 10%, 15%, and 20%. The SEM analysis of soot particle morphology revealed that coated particles constitute over 90% of the total particle sample, with coating content increasing proportionally to the fuel stage ratio. The results obtained from HRTEM indicated that average primary particle sizes increase with the fuel stage ratio. The results of HRTEM and Raman spectroscopy suggest that the nanostructure of soot particles becomes more ordered and graphitized with an increasing fuel stage ratio, resulting in lower oxidation activity. Specifically, soot fringe length increased with the fuel stage ratio, while soot fringe tortuosity and separation distance decreased. In addition, there is a prevalent occurrence of defects in the graphitic lattice structure of soot particles, suggesting a high degree of elemental carbon disorder.

Wood-Derived Graphite: A Sustainable and Cost-Effective Material for the Wide Range of Industrial Applications

The study explored the graphitization of wood through two distinct methods: a high-temperature approach at 2400 °C and a low-temperature technique at 1400 °C using a catalyst. The graphitization properties were assessed by conducting thermal experiments at various temperatures (1100 °C, 1400 °C, 1800 °C, 2000 °C, and 2400 °C), both with and without a catalyst. The development of graphite lattices was quantitatively analyzed using an array of techniques: X-ray diffractometer (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and Fourier transform infrared spectroscopy (FTIR). The XRD analysis highlighted temperature-dependent changes in lattice parameters (d002, La, and Lc), while Raman spectroscopy tracked alterations in the D to G peak ratio (D/G) with temperature. An increase in temperature is correlated with a rise in the number of graphene layers and the degree of graphitization. Notably, the process of graphite lattice formation varied across the experimental temperature spectrum. The use of a catalyst resulted in a reduced d002 spacing, signifying an enhanced degree of graphitization. Moreover, the catalyst promoted a consistent and smooth graphitization process throughout the heating stages. In contrast, graphitization without a catalyst occurred at higher temperatures, specifically between 1800 °C and 2000 °C, with the d002 value stabilizing around 0.338 nm. The catalyst proved instrumental in transforming the initial structure into well-ordered graphite at lower temperatures. This investigation underscores the potential and benefits of employing a catalyst to generate high-quality graphite from wood at reduced temperatures, paving the way for sustainable and economically viable applications of this material.

Nitrogen-doped carbonaceous electrode modified by biological metal-organic framework for vanadium redox flow batteries

The biological metal-organic framework (Bio-MOF) is utilized to modify the carbonaceous electrode for the vanadium redox flow batteries. The microwave solvothermal method prepared the cobalt-based Bio-MOF on a graphite felt (GF) surface. Then, the nitrogen-doping graphite and porous structure formation were completed simultaneously during the carbonization process. Finally, electrochemical activation was conducted to remove cobalt metal from the GF electrode and raise the concentration of oxygen-containing functional group active sites. By in-situ Raman spectroscopy, the increase of disordered graphitic lattices could be observed by raising the potential from 0.6 V to 1.6 V. The microwave solvothermal method and electrochemical activation can effectively shorten the treatment time compared with the traditional solvothermal method and acidic etching processes. Among the carbonization parameters for Bio-MOF-covered GFs, maintaining the temperature at 900 °C for 2 h under an argon atmosphere is the most suitable. The annealed sample after electrochemical activation (BMDGF-900EA) displays 73.7 % energy efficiency at 120 mA cm−2 and possesses a 90 % retention rate of efficiency after 250 cycles at 180 mA cm−2. The superior performance results from more catalytic active sites, hydrophilic surface features, and larger specific surface area prove that this modification method derived from Bio-MOF indeed provides a novel and potential way to improve the VRFB performance.

Nanolithography of the nanocorral structure of chemisorbed oxygen atoms on the graphitic lattice

Controlled atomic patterning is an attractive tool to fine tune properties of graphitic lattice. Several O-functionalized derivatives of graphitic lattice have been widely studied, e.g., graphene oxide, reduced graphene oxide, and functionalized carbon nanotubes. A controlled patterning of chemisorbed O atom is highly desired to fine tune physical and chemical properties, e.g., bandgap, conductivity, hydrophilicity, reactivity, etc. However, patterning of chemisorbed O on the graphitic lattice at the nanometer scale has not been reported. In this study, using scanning tunneling microscopy (STM), we manipulate chemisorbed O (epoxy) on the graphitic lattice, on demand, on the desired atom, on an atom-by-atom basis. We show that chemisorbed O can be desorbed when an energy exceeding the energy barrier for desorption (∼1.3 eV) is supplied as the bias voltage for imaging. This resulted in pristine, defect-free, and clean graphitic lattice at the site of desorption. Nanometer-scale patterns with resolution of oxygen-free regions surrounded by oxygen-rich regions could be achieved by scanning a pre-defined area. A distinct imaging effects was observed with low and high bias voltage-based scanning which is attributed to the local density of states of the O-functionalized graphitic lattice. Overall, the novel atomic-oxygen nanolithography of graphitic surface opens pathways for studying physicochemical properties of the functional groups in nanometer-scale confinement.

Atomic resolution imaging using a novel, compact and stiff scanning tunnelling microscope in cryogen-free superconducting magnet.

We present the design and performance of a novel scanning tunnelling microscope (STM) operating in a cryogen-free superconducting magnet. Our home-built STM head is compact (51.5mm long and 20mm in diameter) and has a single arm that provides complete openness in the scanning area between the tip and sample. The STM head consists of two piezoelectric tubes (PTs), a piezoelectric scanning tube (PST) mounted on a well-polished zirconia shaft, and a large PT housed in a sapphire tube called the motor tube. The main body of the STM head is made of tantalum. In this design, we fixed the sapphire tube to the frame with screws so that the tube's position can be changed quickly. To analyse the stiffness of the STM head unit, we identified the lowest eigenfrequencies with 3 and 4kHz in the bending modes, 8kHz in a torsional mode, and 9kHz in a longitudinal mode by finite element analysis, and also measured the low drift rates in the X-Y plane and in the Z direction. The high performance of the home-built STM was demonstrated by images of the hexagonal graphite lattice at 300 K and in a sweeping magnetic field from 0 T to 9 T. Our results confirm the high stability, vibration resistance, insensitivity to high magnetic fields and the application potential of our newly developed STM for the investigation of low-frequency systems with high static support stiffness in physics, chemistry, material and biological sciences.

Contrasting graphitization differences between vitrinite and inertinite based on high-temperature and high-pressure experiments

It has been recognized that vitrinite and inertinite exhibit different evolutionary characteristics during coalification processs, but the study of their evolutionary differences after entering the graphitization process is limited. To investigate the graphitization differences, this study conducted high-temperature high-pressure (HT-HP) experiments under different temperature and pressure conditions. The precursor used in the HT-HP experiments was concentrated inertinite-rich samples and vitrinite-rich samples obtained through manual selection, and the parent coal is low volatile bituminous coal (Rmax (%) = 1.7). X-ray diffraction (XRD), Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM) were employed to compare and analyze the graphite lattice evolution of the maceral. The experimental results indicated the following: (1) During the construction of the three-dimensional graphite lattice, vitrinite and inertinite exhibited differences in response to temperature and pressure conditions. Inertinite had a higher graphitization threshold compared to vitrinite, and once reached or exceeded, inertinite underwent rapid graphitization seen by the significant decrease of the interlayer spacing d002; (2) In terms of defect healing, under the same stress conditions, vitrinite was more sensitive to temperature compared to inertinite as observed by the Raman parameters R2 and R3; (3) By comparing the development of graphite structure under different temperature and pressure conditions, we found that both efficient graphitization process and development of the graphite structure require a synergistic combination of temperature and pressure, where an excessive or insufficient pressure can inhibit graphitization and even dismantle and damage the formed graphite structure.

Graphene-like materials supported on sepiolite clay synthesized at relatively low temperature

The preparation of solids with graphitic structure usually requires synthesis procedures using very high temperatures. In this work, a comparative study involving different experimental strategies of synthesis at relatively low temperature was carried out to obtain graphene-like materials supported on microporous sepiolite (SEP) clay. The final objective was the optimization of the development of new clay-graphitic nanostructured materials to achieve porous solids while saving energy and time during the preparation stages. The pyrolysis of sucrose (SUC), used as carbon precursor, was accomplished by microwave (MW) pyrolysis or tube furnace (TF) pyrolysis at 200 or 500 °C followed by a hydrothermal carbonization (HTC) step. The resulting carbon-clay nanoarchitectures were characterized by Raman and Infrared spectroscopy, X-ray diffraction, elemental analysis, electron microscopy, and nitrogen adsorption-desorption isotherms. The MW200 and TF200 treatments caramelized SUC and the post-HTC step was fundamental to obtain porous carbonaceous materials. The TF500 pyrolysis produced predominantly crystalline carbon, while the MW500 pyrolysis formed an amorphous material. Moreover, the high-resolution transmission electron microscopy observations of TF500 sample revealed a crystalline material with a d-spacing of 0.33 nm, matching the graphitic lattice. All the treatment conditions performed at 500 °C i.e., MW or TF followed or not by HTC, resulted in mesoporous carbons with a specific surface area above 200 m2 g−1. The MW pyrolysis saved 100 min of the reaction time in comparison to TF pyrolysis to obtain the carbonaceous porous materials.

Uniformity of Electrodeposited Coatings Onto Additively Manufactured Graphite Lattice Electrodes

The ability to uniformly electrodeposit metallic coatings onto geometrically complex substrates plays a significant role in developing specialized applications from coating detailed RF components to depositing catalytic coatings onto ordered foams electrodes for electrochemical flow reactors. However, there presently lacks guidelines for electrodeposition in porous media due to the problem’s multi-scale complexity. We present a framework for deconvoluting this process through continuum-level modeling and experimental validation of electrodeposited copper onto additively manufactured conductive lattice structures. Through numerical simulations we can predict thickness profiles and validate the model prediction and coating quality through micro-computed tomography. We further devise scaling laws with the aim of facilitating control over deposition uniformities on different lattice architectures and dimensions under fluid flow. In extension, the manufacturing platform for functionalized electrodes is extended to battery applications as use in novel electrode geometries within rechargeable secondary batteries as well as plating thickness evolution in custom redox flow battery cathodes for grid scale energy storage.This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 within the LDRD program 20-ERD-056. LLNL-ABS-847849.

Quantifying defects in carbon nanotubes undergoing prolonged electrochemical cycling with Raman phase map

Electrically conducting graphitic carbon materials are ubiquitous constituents of electrocatalysts and electrochemical energy storage materials. During electrolysis and electrochemical charge-discharge cycles, the carbon matrix is subjected to chemical stress due to drastic changes in the redox environment, the formation of reactive intermediate species and to steric strain caused by intercalation of counter ions. These factors trigger the formation of defects in the graphitic lattice, leading to scattering the charge carriers, thereby reducing the carrier mobility. It is of utmost importance to reliably monitor the graphitic lattice to maintain the integrity of the material and recognize the nature of defects. We have applied statistical Raman measurement technique in conjunction with Raman phase map and Raman ellipse to monitor and quantify the formation of point and line defects in functionalized carbon nanotubes. We also demonstrate how the Raman ellipse in combination with ID/ID′ is a new and powerful analytical tool which can serve to deduce the correct defect generation process in a graphitic lattice exposed to stress during electrochemical cycling. Thus, a deep mechanical insight by “simple” optical spectroscopy can be captured through our proposed Raman phase map analysis.

Acoustic real second-order nodal-loop semimetal and non-Hermitian modulation

The unique features of spinless time-reversal symmetry and tunable ℤ2 gauge fields in artificial systems facilitate the emergence of topological properties in the landscape, such as the recently explored Möbius-twisted phase and real second-order nodal-loop semimetals. However, these properties have predominantly been proposed only in theoretical frameworks. In this study, we present a cunningly designed blueprint for realizing an acoustic real second-order nodal-loop semimetal through the incorporation of projective translation symmetry into a three-dimensional stacked acoustic graphitic lattice. Additionally, we introduce non-Hermitian modulation to the topologically protected propagation of degenerate drumhead surface and hinge states, which depend on the specific on-site gain and loss textures. It should be emphasized that this demonstration can be extended to other classical wave systems, thereby potentially opening up opportunities for the design of functional topological devices.

Pentagon Defects Accelerating Polysulfides Conversion Enabled High‐Performance Sodium–Sulfur Batteries

AbstractPorous carbon materials with high electrical conductivity and superior mechanical strength have been demonstrated to be one of most promising sulfur hosts for room‐temperature sodium–sulfur (RT Na–S) batteries. However, the nonpolar surface of intact graphite lattice displays weak interaction toward the polar polysulfides, thereby resulting in the notorious shuttle effect and poor sulfur conversion kinetics. Herein, pentagon defects are designed into the graphite lattice to break the integrity of π‐conjugation, making the localized electron distribution to simultaneously enhance the polysulfide affinity and accelerate sulfur conversion kinetics. Notably, the as‐synthesized carbon materials as the sulfur host exhibit a high reversible capacity of 1275 mAh g−1 at 0.1 C after 100 cycles and long‐term cycling stability with low‐capacity decay of only 0.035% per cycle at 3 C over 600 cycles. Density functional theory calculations and electrochemical experiments confirm that pentagon defects could efficiently accelerate the chemical interaction between pentagon carbon atoms and polysulfides, and markedly lower the sulfur conversion kinetics in comparison with intact graphene. This research offers a basis for designing intrinsic pentagon defects in carbon materials as efficient catalysts for RT Na–S batteries.

Study the effect of ZnO additive in rGO/ZnO nanocomposites for the investigation of ammonia sensing characteristics

This study reports the synthesis and gas-sensing properties of reduced graphene oxide (rGO), zinc oxide nanoparticles (ZnO NPs), and their nanocomposites (rGO/ZnO NCs). ZnO NPs, rGO, and rGO/ZnO NCs were synthesized using the co-precipitation, modified Hummers method, and the ultrasonic-assisted technique, respectively. The XRD diffraction patterns confirmed the presence of graphitic lattice planes in rGO and the formation of hexagonal ZnO NPs. SEM micrographs revealed the wrinkled sheet-like morphology of rGO and the distribution of ZnO NPs over the rGO surface. The UV–Vis spectroscopy indicated the rGO and ZnO NPs peaks in NC spectrum. FTIR spectroscopy analysis showed the purity of synthesized specimens. Among the samples, ZnO NPs and rGO/ZnO (70/30) NC-based sensors exhibited the best capacitive and resistive response within the 2.5–36 ppm range at 100 Hz, with the later showing quick response/recovery time of 12 s/20 s at 36 ppm. The fabricated sensors also displayed long-term stability and excellent selectivity.

Experimental study on the catalytic effect of AAEMs on NO reduction during coal combustion in O2/CO2 atmosphere

During oxy-fuel combustion, the NO emission can be inhibited by the strongly reductive atmosphere caused by the high proportion of gasification reaction, which is a unique feature that differs from air combustion. The alkali and alkaline earth metals (AAEMs) contained in coal ash can catalyze gasification reactions, promoting the homogeneous reduction process of NO. Besides, AAEMs also suppress NO emission through catalyzing the NO heterogeneous reduction by char (CNO). Both catalytic effects of AAEMs have been studied at relatively low temperatures (below 1000 °C) in a simple atmosphere (pure CO2). However, the catalytic effect of AAEMs on NO reduction is still unclear during oxy-fuel combustion due to the more complex reaction atmosphere, higher reaction temperatures, and the presence of gasification reactions. In this work, the effect of different factors on the catalytic effect of AAEMs under O2/CO2 atmosphere is investigated. Results show that the order of the catalytic effect of AAEMs on NO reduction is Na > K > Ca > Mg, with the highest NO reduction efficiency of 30 % for Na. The catalytic effect of Na on NO reduction weakened as the temperature increases. When the temperature increased from 1373 K to 1573 K, the NO reduction efficiency (ηNO) of Na decreased from 30 % to 6 %. While the catalytic effect of Na on NO reduction strengthened as the oxygen concentration increases. When the O2 concentrations increased from 10 vol.% to 30 vol.%, the ηNO values of Na increased from 27 % to 35 %. The K-Na binary additive is more effective in reducing NO emissions than K and Na alone, with NO reduction efficiency as high as 46.8 % at a K/ Na is 1:2. Besides, the Raman test results reveal that K contributed to the conversion of amorphous carbon into a regular graphite crystal structure. Na disrupted the graphite structure resulting in more defective points appearing in the graphite lattice. These results are expected to provide a theoretical reference and new insights for the reduction of NO emission during oxy-fuel combustion.

A 2D Nano-architecture (NPSMC@Ir-Ru@rGO) Derived from Graphene Enfolded Polyphosphazene Nanospheres Decorated Ir-Ru Metals (PZS@Ir-Ru@GO) towards Bifunctional Water Splitting.

A leap-forward approach has been successfully devised to synthesize a novel hierarchical binary metal modified heteroatom doped 2D micro-/mesporous carbon-graphene nanostructure (NPSMC@Ir-Ru@rGO) for overall water splitting application. To investigate the role of decorating metals, different electrolcatalysts like NPSMC, NPSMC@rGO, NPSMC@Ir@rGO, and NPSMC@Ru@rGO were also synthesized and structural changes were compared and investigated by physiochemical techniques. All of the samples have shown electrocatalytic activities attributed to the presence of heteroatom (N, P, S) doped micro-/mesoporous carbonaceous matrix, amorphous carbon in the coexistence of graphitic lattice carbons, presence of active metal NPs (Ir and/-or Ru), an even distribution of active sites, and graphene 2D interconnected channels to promote electron transfer ability, respectively. However, the Ir-Ru metal codeped nanocatalyst (NPCMS@Ir-Ru@rGO) is proved to be an excellent electrocatalyst based on the synergistic role of Ir-Ru metals that necessitates the low overpotentials of 181 mV and 318 mV to convey a current density of 10 mA cm-2 towards the electroctalytic application of HER and OER, respectively. Furthermore, exhibiting the corresponding Tafel slopes (132 and 70 mV dec-1 ) in an alkaline medium. This work is anticipated to open up new avenues for the development of promising electrocatalysts based on active metals modified heteroatom doped carbon nanomaterials for energy applications.

Unraveling the Oxidation of a Graphitic Lattice: Structure Determination of Oxygen Clusters.

Unraveling the oxidation of graphitic lattice is of great interest for atomic-scale lattice manipulation. Herein, we build epoxy cluster, atom by atom, using Van der Waals' density-functional theory aided by Clar's aromatic π-sextet rule. We predict the formation of cyclic epoxy trimers and its linear chains propagating along the armchair direction of the lattice to minimize the system's energy. Using low-temperature scanning tunneling microscopy on oxidized graphitic lattice, we identify linear chains as bright features that have a threefold symmetry, and which exclusively run along the armchair direction of the lattice confirming the theoretical predictions.