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A phosphorus and nitrogen co-doped carbon material (PNDC) was synthesized from aminated tannin and polyphosphoric acid by a rapid and highly efficient microwave synthetic technique. X-ray photoelectron spectroscopy study was useful in the identification of nitrogen and phosphorous environments in a sp 2 hybridized carbon lattice. The PNDC was found to be a porous material with a surface area of 433 m 2 g −1 . PNDC sample exhibited excellent thermal stability and the Raman spectroscopic studies were used for analyzing defects in the sp 2 hybridized carbon lattice. This material has promising electrochemical applications, especially for catalyzing oxygen reduction reaction in fuel cells and for charge storage in supercapacitors. The oxygen reduction capability of PNDC was investigated in 0.1 M KOH solution, and rotating disk and ring disk electrode studies were performed to identify the mechanism of oxygen reduction. The capacitative behavior of the PNDC was investigated in 6 M KOH and specific capacitance was determined to be 161 F g −1 due to the electric double layer charge storage phenomenon. [ABSTRACT FROM AUTHOR]

Abstract: Silicon-doped self-sintering carbons have been prepared by co-pyrolysis of an aromatic petroleum residue with silicon containing compounds (triphenylsilane or diphenylsilane) at 440°C and a pressure of 1.0MPa, with varying silicon content and soak time. Analysis of the solid pyrolysis products indicates that silicon inhibits mesophase formation and slightly accelerates the formation of material insoluble in 1-methyl-2-pyrrolidone (constituted by the heaviest molecules of the solid), especially when using the less substituted silane. The pyrolysis products have been extracted with toluene to obtain self-sintering carbon powders. The thermomechanical analysis of the self-sintering powders indicates that thermofusibility is restricted by the presence of silicon. By selecting the appropriate pyrolysis conditions it is possible to obtain heat-treated samples (2100°C) with density and mechanical properties superior to the undoped ones, reaching values of 130MPa of bending strength and 21GPa of Young modulus. [Copyright &y& Elsevier]

Abstract: The co-pyrolysis of a petroleum residue with two different sources of titanium (tetrabutyl-ortotitanate (TBO) or titanium carbide nano-powder) was carried out to obtain mesophase pitches containing TiO2 or TiC nanoparticles. Co-pyrolysis is an appropriate technique to achieve a good dispersion and low particle size. In the case of TBO, TiO2 nanoparticles (5–20nm) are observed, which are forming aggregates, the largest of them being 1–2μm. In the case of TiC nano-particles, they are more difficult to disperse and larger aggregates are formed, although the final material is rather homogenous. The chemistry of pyrolysis for the production of doped and undoped mesophase pitches has been followed by means of solvent insolubility, XRD, XPS, FTIR and elemental analysis. They show evidences of promotion of the formation of mesophase in the presence of the titanium-containing particles, especially in the presence of TiO2. The final materials can be of great value as precursors to produce high density titanium doped graphites for nuclear and space applications. [Copyright &y& Elsevier]

Abstract: First-principle calculations using quantum-mechanical density functional theory are carried out to study nitrogen incorporation in amorphous carbon, in which the structural models from liquid quench containing 64 atoms are introduced. The properties simulated for N incorporated amorphous carbon are in agreement with the available experimental results. The topological and electronic properties for nitrogen incorporation structures with various densities are investigated, and it is found that the bonding configuration of nitrogen atoms strongly depends on the density and the nitrogen concentration in the network. The simulations provide a qualitative support for a low nitrogen doping efficiency observed in the experiment since no true doping (N atoms substitutionally occupy C sites, leading to a donor level below conduction band mobility edge E c ) exists in any cases studied. For the tetrahedral amorphous carbon (at density of 2.9 g/cm3) with a low concentration of nitrogen (1.6 at% and 3.2 at%), the incorporated N atoms are found to adopt the auto-compensated sites or to be in threefold coordination. In particular, a new threefold C defect is found, which is introduced by nitrogen auto-compensation. Nitrogen incorporated amorphous carbon (2.0 g/cm3) leads to the formation of a graphite-like structure with twofold nitrogen coordination. [Copyright &y& Elsevier]

Abstract: The combination of PM3 semi-empirical method for geometry optimization, and ab initio DFT (density functional theory) for energy calculation, is used to study the configurations of hydrogen molecules at 0K within the vacuum of C60 fullerene and carbon nanocapsules. The obtained structural information including the molecular arrangement and structural state of the clusters of H2 are mainly determined by two kinds of repulsive energies, namely that between the H2 molecules and the wall of the spheroidal or capsule like carbon structure, and that between interacting H2 molecules. It is further established that the repulsive energy among the H2 molecules is not purely a function of the number of encapsulated H2, and there is a tradeoff between the two kinds of repulsive energies. [Copyright &y& Elsevier]

Phosphorus-doped amorphous carbon (n-C:P) films were grown by r. f.-power-assisted plasma-enhanced chemical vapor deposition at room temperature using a novel solid red phosphorus target. The influence of phosphorus doping on material properties of n-C:P based on the results of simultaneous characterization are reported. Moreover, the solar cell properties such as series resistance, short circuit current density, open circuit current voltage, fill factor and conversion efficiency along with the spectral response are reported for the fabricated carbon-based n-C:P/p-Si heterojunction solar cell that was measured by standard measurement technique. The cells performances have been given in the dark I–V rectifying curve and I–V working curve under illumination when exposed to AM 1.5 illumination condition (100mW/cm2, 25°C). The maximum of open-circuit voltage (Voc) and short-circuit current density (Jsc) for the cells are observed to be approximately 236 V and 7.34,mAcm2 respectively for the n-C:P/p-Si cell grown at lower r. f. power of 100 W. The highest energy conversion efficiency (η) and fill factor (FF) were found to be approximately 0.84% and 49%, respectively. We have observed that the rectifying nature of the heterojunction structures is due to the nature of n-C:P films. [ABSTRACT FROM AUTHOR]

Carbon materials of boron content ranging from 0.6 to 4 wt.% were synthesized by co-pyrolysis of QI-free coal–tar pitch with the borane–pyridine complex. The growing amount of boron introduced into the carbonaceous material is associated with an increase in nitrogen content and a progressive degradation of structural and textural ordering. The structural variations of the boron-doped materials on heat treatment up to 2500 °C were monitored using X-ray diffraction and X-ray photoelectron spectroscopy. The intrinsic boron acts effectively as a catalyst of graphitization above 2100 °C. The carbonaceous material with boron content of about 1.5 wt% shows the highest degree of structural ordering after thermal treatment. A high amount of oxygen was found in the graphitized boronated carbons, proving that the incorporated boron induces a strong chemisorption activity of the material when exposed to air. For a series of cokes calcined at 1000 °C, the most striking effect of increasing the boron content is an increase of irreversible capacity Xirr from 0.2 to 0.7. The reversible capacity (Xrev) amounts to about 1, with a slight tendency to decrease with the boron content. Upon increasing the temperature up to 2500 °C, Xirr decreases to about 0.1 in the graphitic carbons, while Xrev reaches a minimum of 0.4–0.5 at 1700 °C and next increases to a value close to 1 at 2500 °C. In the boron doped graphite, Xirr has a slight tendency to increase with the boron content, due to the simultaneous presence of nitrogen in these materials and their strong affinity for oxygen from the atmosphere. [Copyright &y& Elsevier]

Catalytic graphitization of carbon laminations was carried out using mesocarbon microbeads as the matrix precursor. Aqueous tape casting was used to prepare the carbon laminations, which were doped separately with Ti, ZrO2 and B4C powders. After sintering at 1400 °C in a vacuum, these dopants were found to enhance the degree of graphitization and improve the properties of the laminations. Ti was the most effective catalyst of the three dopants. The effects of binary dopants on the graphitization process and properties of the resulting laminations were also tested, but the catalytic effect of binary dopants was found to be less than that shown by single additives. [Copyright &y& Elsevier]

On the design of efficient and affordable electrocatalysts for water reduction half reaction, this paper fabricates molybdenum carbide nanoparticles uniformly loaded in highly porous N-doped carbon matrix derived from polyaniline-molybdate monolith with the use of graphitic carbon nitride (g-C 3 N 4 ) as template. The obtained molybdenum carbide-carbon hybrid catalysts (MoC@NCS) exhibit extraordinarily electrochemical hydrogen evolution activity with a small overpotential of 89 and 81 mV to deliver a current density of 10 mA cm -2 in alkaline (1.0 M KOH) and acidic (0.5 M H 2 SO 4 ) medium, respectively, even comparable to noble-metal Pt/C benchmark. Specially, MoC@NCS also shows excellent long-term durability in alkaline or acidic electrolyte. Furthermore, the obtained carbon matrix (NCS) featuring high content of N dopants and hierarchically porous architecture exhibits high catalytic efficiency for oxygen evolution reaction in alkaline electrolyte. For a further step, the obtained NCS coupled with the MoC@NCS, working as anodic and cathodic electrodes, in a two-electrode alkaline electrolyzer for overall water splitting, which can obtain a current density of 10 mA cm -2 at 1.69 V, along with robust operation durability. The synergistic effect of the porous carbon matrix of high nitrogen content and the molybdenum carbide nanoparticles of uniform distribution, together with hierarchically porous structure, should be responsible for the outstanding electrocatalytic HER performance. This work presents an easy and cost-effective strategy to prepare molybdenum-based materials with controlled size for electrocatalytic hydrogen evolution.

In spite of being technologically feasible, electrochemical water reduction to facilitate hydrogen production is confronted with issues mainly due to the lack of affordable and efficient catalysts for the water reduction half reaction. Reported herein is the fabrication of metal phosphides nanocrystals uniformly loaded on highly porous heteroatom-modified carbons through one-step carbonization-phosphization methodology. Remarkably, the well-structured porosity and the increased electrochemically accessible active sites ensure the high catalytic efficiency for electrochemical hydrogen evolution in acidic medium in terms of small onset potentials (33 mV) and large cathodic current density (0.481 mA cm(-2)), even comparable to the state-of-the-art Pt/C benchmark. The easily prepared composite catalysts of structural and textural peculiarities may serve as promising non-noble metal catalysts for realistic hydrogen evolution.