The development of appropriate anode material for lithium-ion batteries that can support operation under low ambient temperatures is necessary. Here, bromine-free and bromine-doped porous nitrogen-doped carbon materials were tested as anodes in lithium-ion batteries at the operation temperatures from 25 to -20 degrees C. The nitrogen-doped carbon material was synthesized from acetonitrile and calcium glutarate and demonstrated high reversible capacity of 907 mAhg-1 at current density of 0.1 Ag-1 and 462 mAhg-1 at 2 Ag-1. The content of 2 at % of bromine (Br) in forms of covalently bonded Br atoms and adsorbed Brn-molecules was achieved by interaction of material with Br2 vapor. The brominated material showed increased capacity of 1101 mAhg-1 at 0.1 Ag-1 and 612 mAhg-1 at 2 Ag-1 due to additional lithium capture by bromine-containing functional groups. Lowering the operation temperature from 25 to -20 degrees C resulted in 59 % capacity retention for the initial sample and 51 % for the brominated analogue of their capacity at 2 Ag-1. The high capacity retention was explained by fast kinetics of adsorption reaction of lithium with carbon electrodes due to nitrogen-and bromine-based functional groups, and high mesoporosity.

Filling cavities in single-walled carbon nanotubes (SWCNTs) opens up additional opportunities for modifying their surface physicochemical properties. Here, we use a vaporization-condensation method to encapsulate individual phosphorus and sulfur and their mixtures and study the effect of filler composition on the gas sensor properties of SWCNTs with respect to nitrogen dioxide exposure. The introduction of a filler leads to significant improvement in the sensor's response to low concentrations of nitrogen dioxide in the air by enhancing charge transfer, reducing the number of adsorption sites inside the bundles/nanotubes, and lowering the adsorption energy. Sensors based on filled SWCNTs exhibit a calculated detection limit of 2-7 ppb NO2 at a response time of less than 1 min, long-term stability of more than one year, and exceptional selectivity to NO2.

The synergistic combination of sp2-and sp3-hybridized carbons has multiple applications. Among various structural parameters, the texture of the interface layer in sp2-sp3 composites is perhaps one of the most important factor affecting their functional properties. In the present study, we investigated the early stages of graphitization of a synthetic diamond during high-vacuum annealing at 1250 degrees C. This was achieved using high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and angle-resolved near-edge Xray absorption fine structure spectroscopy in combination with density functional theory modeling. Our results showed that the texture of the graphitized layer can be controlled by the symmetry of the annealed diamond crystal face and by defect engineering. Specifically, arches merging with the diamond layer were formed on the (100) face, while nanographites were formed on the (111) face. In the latter case, the graphene sheets had a predominantly vertical orientation to the crystal face and could grew parallel in the etch pits. The stages of the structural evolution of diamond graphitization are discussed, including the rearrangement of the diamond surface, the detachment of carbon atoms, the formation of an amorphous sp2 carbon layer, and its subsequent condensation into nanographite covalently bonded to the diamond surface.

Hybrid materials consisting of molybdenum disulfide (MoS2) and graphitic-like carbon have great potential for practical application as anodes in high-performance sodium-ion batteries. In this work, to reveal the effect of carbon coating on the interaction of sodium with the MoS2 layers located vertically relative to the substrate, model experiments were carried out using synchrotron-radiation-induced X-ray photoelectron spectroscopy (XPS). Sodium vapor obtained by heating a sodium source was simultaneously deposited in vacuum on the surfaces of MoS2, pyrolytic carbon, and a hybrid sample obtained by transferring a pyrolytic carbon film onto the MoS2 film. According to XPS data, sodium easily penetrates into the space between the vertical layers of the uncoated film, and its interaction with MoS2 leads to the transformation of the original hexagonal structure into a distorted tetragonal one. Under the experimental conditions, sodium is unable to diffuse through the carbon film consisting of horizontally oriented graphene domains and is almost completely removed by annealing the sample at 773 K in ultrahigh vacuum. The presence of the underlying MoS2 film facilitates the diffusion of sodium through the graphitic coating, but not all of the deposited sodium reaches MoS2. As a result, the sodium-induced rearrangement of the carbon-coated MoS2 is less than that of the free MoS2 film, and annealing of the sodiated sample restores its structure. The obtained results demonstrate the important role of the graphitic coating in the development of viable MoS2-based electrodes for energy storage systems.

Effect of carbon on the interaction of lithium with highly stable nitrogen molecule requires study for practical use in energy storage and electrochemical nitrogen reduction. In this work, we consider the interaction of lithium with nitrogen molecules embedded in defective multilayer graphene using synchrotron X-ray spectroscopy. Multilayer graphene synthesized by chemical vapor deposition was bombarded with 1 keV nitrogen ions to create lattice defects and insert similar to 10 at.% nitrogen, and then used for lithium vapor deposition. All modifications of the graphene sample were carried out under ultra-high vacuum conditions and accompanied by measurements of X-ray photoelectron and near-edge X-ray absorption fine structure spectra. Analysis of the spectra revealed the formation of intercalated N-2 molecules as a result of bombardment of graphene and their covalent interaction with deposited lithium. According to density functional theory calculations, the valence orbitals of N-2 and Li hybridize with the pi-orbitals of graphene, which increases the bonding between the intercalants. This finding provides new insights into the processes occurring in N-2-intercalated graphene-based electrode materials during lithiation and can be used to develop efficient lithium-based electrochemical energy storage systems and electrochemical approaches for N-2 reduction reaction.

MoS2 coatings were formed on surface-oxidized silicon, chemical vapor deposition (CVD)-grown graphene, and reduced fluorinated graphene (rFG) from ammonium tetrathiomolybdate. The samples were annealed under ultra-high vacuum conditions at a temperature of 1000 degrees C. Analysis of X-ray photoelectron and X-ray absorption spectra revealed a bonding between MoS2 and the supporting material that was particularly strong for CVD-graphene. Uniform covering of the flat CVD-graphene surface with MoS2 nanoparticles and numerous contacts between them promoted the removal of sulfur and the formation of exposed molybdenum edges. A cracked MoS2 coating consisting of dense domains was formed on the wrinkled rFG surface. The study of samples as NO2 gas sensors revealed the best performance of MoS2/CVD-graphene. The sensor detected NO2 in air below 50 ppb at room temperature, had good response and recovery, operated in humid air, and demonstrated excellent NO2 selectivity. The other two sensors gave signals at elevated temperatures. The advantage of MoS2/CVD-graphene is due to improved electron transport in the hybrid, accessibility of small MoS2 nanoparticles to the analyte, and passivation of high-energy molybdenum sites by oxygen, which improves NO2 desorption. [Graphics]

Lithium- and sodium-ion batteries (LIBs and SIBs) suffer from the significant degradation of electrochemical performance at low temperatures. This work presents promising hybrid anodes synthesized by the rapid thermolysis of ammonium tetrathiomolybdate and graphene oxide (GO) at 600 and 700 °C. Transmission electron microscopy revealed the formation of MoS2 crystallites oriented along or perpendicular to the surface of reduced GO (rGO) layers. X-ray photoelectron spectroscopy found the covalent C-S bonds connecting components in the MoS2/rGO hybrids. The MoS2/rGO_600 hybrid showed higher specific capacities in LIBs of 1370 mAh/g, 835 mAh/g, and 711 mAh/g at a current density of 0.1 A/g and temperatures of 25 °C, 0 °C, and -20 °C, respectively, due to the presence of excess sulfur in the sample. Increasing the current density to 2 A/g retained 78 and 34% of the capacity at 25 °C and -20 °C. In SIBs, the MoS2/rGO_700 hybrid showed more promising results, achieving 550 mAh/g at 0.1 A/g and 400 mAh/g at 2 A/g, while lowering the temperature to -20 °C retained 48 and 17% of the capacity. Such good SIB performance is attributed to the enrichment of the sample with vertically oriented MoS2 layers covalently bonded to the rGO surface.

Controlling high-temperature graphitization of diamond surfaces is important for many applications, which require the formation of thin conductive electrodes on dielectric substrates. Transition metal catalysts can facilitate the graphitization process, which depends on the diamond face orientation. In the present work, the role of a nickel coating on the electronic structure and chemical state of graphite layers formed on the surface of a polycrystalline diamond (PCD) film with mixed grain orientation was studied. A synthetic single-crystal diamond (SCD) with a polished (110) face was examined for comparison. The samples were coated with a thin nickel film deposited by thermal evaporation. The graphitization of diamond with and without a nickel coating as a result of high-vacuum annealing at a temperature of about 1100 °C was studied in situ using synchrotron-based X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) methods. XPS data revealed the formation of a thin graphite-like film with low-ordered atomic structure on the surface of the nickel-coated PCD film. The chemical state of sp2-hybridized carbon atoms was found to be insensitive to the face orientation of the diamond micro-sized crystallites; however, the layer defectiveness increased in areas with fine-dispersed crystallites. According to NEXAFS and Raman spectroscopy data, the most ordered atomic structure of graphitic layers was obtained by annealing nickel-coated SCD. The angular dependence of NEXAFS C K-edge spectra of nickel-coated (110) face after annealing discovered the vertical orientation of sp2-hybridized carbon layers relative to the diamond surface. The observed behavior suggests that sp2 carbon layers were formed on the diamond surface due to its saturation by released carbon atoms as a result of etching by nickel.

Nitrogen-doped carbon attracts researchers as a catalyst support due to its ability to provide high dispersion of deposited metal, which can show improved properties in various catalytic reactions as compared to the metal on nitrogen-free carbon supports. Here, we developed a procedure for modification of a porous carbon material by fluorination with bromine trifluoride vapor at room temperature followed by heating in gaseous ammonia to produce a nitrogen-doped carbon support for nickel catalyst. The obtained support has a specific surface area of 1030 m(2)/g and a total nitrogen content of 4.8 at.%, with half of it in the form of pyridinic nitrogen, which is necessary for stabilization of nickel atoms. These characteristics of the support allow a simple impregnation method to achieve a content of nickel single-atom sites up to 4.9 wt.%. Increasing the metal content to 7.4 wt.% leads to the formation of nickel particles with an average size of less than 1 nm. The catalysts were tested in the decomposition reaction of gaseous formic acid and showed high (>99 %) and stable selectivity toward hydrogen production.

The Kα and Kβ X-ray emission spectra of sulfur and phosphorus encapsulated within single-walled carbon nanotubes are measured using a laboratory X-ray spectrometer for the first time. The obtained spectra are compared with those of their bulk counterparts, namely, plastic sulfur and red phosphorus. Models of sulfur and phosphorus chains are constructed both in their free state and when encapsulated in nanotubes. Quantum chemical calculations are performed to analyze the distribution of the 3p electron density in the valence band. A strong correlation is observed between the positions of the theoretical bands and the shapes of the experimental Kβ spectra. By comparing the spectra of free and encapsulated sulfur and phosphorus, we analyze their electronic interactions with the walls of carbon nanotubes. This analysis identifies specific features in the electronic structure of the models that contribute to the observed doping behavior in the nanotubes.

Tungsten disulfide (WS2) is attractive for the development of chemiresistive sensors due to its favorable band gap, as well as its mechanical strength and chemical stability. In this work, we elaborate a procedure for the synthesis of thin films consisting of vertically and/or horizontally oriented WS2 nanoparticles by sulfurizing nanometer-thick tungsten layers deposited on oxidized silicon substrates using magnetron sputtering. According to X-ray photoelectron spectroscopy and Raman scattering data, WS2 films grown in an H2-containing atmosphere at 1000 °C are almost free of tungsten oxide. The WS2 film’s thickness is controlled by varying the tungsten sputtering duration from 10 to 90 s. The highest response to nitrogen dioxide (NO2) at room temperature was demonstrated by the film obtained using a tungsten layer sputtered for 30 s. The increased sensitivity is attributed to the high surface-to-volume ratio provided by the horizontal and vertical orientation of the small WS2 nanoparticles. Based on density functional calculations, we conclude that the small in-plane size of WS2 provides many high-energy sites for NO2 adsorption, which leads to greater charge transfer in the sensor. The detection limit of NO2 calculated for the best sensor (WS2-30s) is 15 ppb at room temperature and 8 ppb at 125 °C. The sensor can operate in a humid environment and is significantly less sensitive to NH3 and a mixture of H2, CO, and CO2 gases.

Creating holes in single-walled carbon nanotubes and shortening the encapsulated red phosphorus chains improves lithium accommodation in the nanomaterial.

This article presents the first experiments on filling single-walled carbon nanotubes (SWCNTs) with the phosphorus sulfides P4S3 and P4S10 using the ampoule method. Transmission electron microscopy examination reveals the encapsulation of phosphorus and sulfur species inside the cavities of SWCNTs without the formation of any regular structures. X-ray photoelectron spectroscopy observes different oxidation states of P and S atoms, depending on the P/S ratio in the initial mixture used to fill the nanotubes. The Raman signals associated with the encapsulated species are low in intensity, and the vibrational modes are shifted and broadened as compared to those in crystalline P4S3 and P4S10. The proposed models for the arrangement of sulfur and phosphorus inside SWCNTs suggest the formation of 1D amorphous glassy phosphorus sulfides with stoichiometric ratios close to those of elemental phosphorus and sulfur in the initial mixtures.

Formic acid is a liquid organic hydrogen carrier from which hydrogen can be released together with CO2 by catalytic decomposition. The development of supported Ni catalysts for H-2 production is important. Here, the effects of Ni state/dispersion are considered. For this purpose, three samples were prepared with about 3 wt% Ni deposited on porous N-doped carbon. The first sample contained predominantly Ni nanoparticles (similar to 2 nm), the second contained Ni clusters (<1 nm), and the third - single-atom Ni sites. The catalysts showed close activity in the gas-phase reaction. However, a minimum apparent activation energy of 105 kJ/mol and a maximum selectivity towards H-2 production of 99% were achieved for the single-atom Ni catalyst. The nature of its singleatom sites was established to correspond to Ni-N-4 and Ni-O-4, which showed greater stability under the conditions of the catalytic reaction.

In our study, we annealed polycrystalline diamond films with nanometer-thick iron coatings. Based on analysis of X-ray photoelectron spectroscopy data the presence of two catalytic processes was suggested. One is the continuous absorption of sp3 carbon by iron nanoparticles with subsequent extrusion of the sp2 phase from the formed iron carbide, which leads to the creation of deep tracks into the diamond bulk that are filled with graphite stacks. The other process involves a thin layer of iron carbide on the surface and results in the creation of sp2 layers, which are made up of fused graphene-like patches and are oriented mainly along the surface of the diamond film. For the sample annealed at 800 degrees C for 1 h, the sp2 layers formed exhibit semi-metallic conductivity with quantum corrections caused by disorders. At the same time, no evidence of iron contribution in conductivity of the annealed Fe-coated film was detected, implying that upon transforming the diamond, iron moved quite deep into the bulk. In addition, the formed conductive layer on the diamond surface shows mechanical stability, ensuring the reproducibility of conductivity measurements even after six months of storage in air. The study has revealed the potential for targeted metal-assisted formation of sp2 carbon-based conducting pathways on diamond surfaces for electronic devices.

Edge functionalization of graphene planes with nitrogen improves the electrochemical performance of carbon anode materials in sodium-ion batteries. We propose a route for the synthesis of nitrogen-doped carbon materials with a nitrogen content of 6 at.%, half of which is pyridinic and pyrazole-like nitrogen. By simultaneous thermal decomposition of iron tartrate and acetonitrile vapor at 600 degrees C, nitrogen-doped carbon with embedded nano-particles of iron carbides and iron nitride was synthesized. Heating this composite in air at a temperature of 250 degrees C followed by treatment with hydrochloric acid yields a highly porous carbon material. The oxidation and purification procedures do not affect the total nitrogen content, but result in the formation of pyrazole-like nitrogen at the edges of the graphitic layers. The developed material exhibits an improved capacity of 281-144 mAh g(-1) at current densities of 0.05-1 A g(-1) in sodium-ion battery.

Metal-organic framework (MOF)-derived carbon composites have been considered as the promising materials for energy storage. However, the construction of MOF-based composites with highly controllable mode via the liquid-liquid synthesis method has a great challenge because of the simultaneous heterogeneous nucleation on substrates and the self-nucleation of individual MOF nanocrystals in the liquid phase. Herein, we report a bidirectional electrostatic generated self-assembly strategy to achieve the precisely controlled coatings of single-layer nanoscale MOFs on a range of substrates, including carbon nanotubes (CNTs), graphene oxide (GO), MXene, layered double hydroxides (LDHs), MOFs, and SiO2. The obtained MOF-based nanostructured carbon composite exhibits the hierarchical porosity (V-meso/V-micro: 2.4), ultrahigh N content of 12.4 at.% and "dual electrical conductive networks." The assembled aqueous zinc-ion hybrid capacitor (ZIC) with the prepared nanocarbon composite as a cathode shows a high specific capacitance of 236 F g(-1) at 0.5 A g(-1), great rate performance of 98 F g(-1) at 100 A g(-1), and especially, an ultralong cycling stability up to 230 000 cycles with the capacitance retention of 90.1%. This work develops a repeatable and general method for the controlled construction of MOF coatings on various functional substrates and further fabricates carbon composites for ZICs with ultrastability.

The development of ultrafast opto-electronic devices made of carbon nanotubes (CNTs) requires a deep understanding of the picosecond-scale charge carrier dynamics triggered by the femtosecond irradiation, along with the influence of doping on the photoconductivity. Among CNT doping techniques, CNT filling produces the most time-stable Fermi-level shift since CNTs protect the filling material from the environment. As a result, filled CNTs are ideal for studying the impact of doping on the charge carrier dynamics. We fabricate films of phosphorous-filled and pristine CNTs and measure their transient photoconductivity by optical pump-terahertz probe technique. We employ the semi-classical transport theory to explain the experiment and extract the relevant dynamic parameters. Our calculations imply that the Fermi-level shift originating from the phosphorus filling makes carrier multiplication efficiency increase up to 1.5 with feather tunability. Results firmly establish filled CNT films as a stable and attractive material for diverse opto-electronic applications.

The development of efficient anodes for sodium-ion batteries requires a deep understanding of the electrochemical processes involved. Herein, X-ray spectroscopy is used to study changes in the electronic structure of MoS2 nanosheets coupled with few-layered graphene at early stages of battery life. Working electrode is combined with a sodium plate and a solution of NaClO4 in ethyl carbonate/dimethyl carbonate in a homemade cell having an X-ray transparent window. X-ray absorption spectra at the S K-edge and Mo L3-edge are recorded using a synchrotron source, X-ray emission S K alpha and Mo L alpha spectra are obtained on a laboratory spectrometer for initial powder and electrode material at different potentials of the cell. Analysis of the spectra shows the occupation of the initially empty orbitals of MoS2 by sodium electrons as a result of the interaction of the components of the sodium-ion half-cell. Ex situ X-ray photoelectron spectroscopy measurements of a fully discharged electrode material reveal partial transformation of hexagonal MoS2 to disordered tetragonal MoS2 coated with a surface electrolyte interphase layer. The obtained results indicate that coupling MoS2 to graphene prevents the breaking of Mo-S bonds when Na+ ions are first introduced, which may promote stable battery performance.

Уважаемые коллеги!Благодарим Вас за проявленный интерес к Четвертой российской конференции «Графен: молекула и 2D кристалл» и желание принять участие в её работе.Конференция проходит в научно-образовательном центре города Новосибирска -Академгородке.Мероприятие посвящено актуальным направлениям исследований и разработок в области углеродных и низкоразмерных материалов.Проведение конференции поможет координации усилий ученых в решении современных проблем материаловедения и привлечению молодых исследователей для решения актуальных научных задач.Оргкомитет выражает особую благодарность НГУ, Центру компетенций НТИ «Моделирование и разработка новых функциональных материалов с заданными свойствами», компаниям «Диаэм», «НТ-МДТ Спектрум Инструментс» и корпорации "Графеновая Долина" за финансовую поддержку и журналам Аналитика, Наноиндустрия и РЭНСИТ за информационную поддержку.Искренне надеемся, что пребывание в Новосибирском Академгородке и в стенах Новосибирского государственного университета оставит множество положительных эмоций и