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Graphene materials exhibit extraordinary properties, but are difficult to produce. The present work describes the possibility of using a plasma process to exfoliate and functionalize graphite flakes. An impulse plasma phase is generated at a liquid surface to produce chemical species and shock waves in order to modify the reactive liquid as well as the graphite flakes. With this process, industrial graphite was treated. 20% thickness diminution was observed, and the formation of a random turbostratic structure. The exfoliation occurs with small amount of functionalization of the surface. Even after treatment, the graphite flakes present a low defect density compared with other treated graphite obtained by more conventional chemical treatments. This process is a new way to exfoliate graphite and to produce functionalized graphenic materials. [ABSTRACT FROM AUTHOR]

For the purpose of synthetizing 3-dimensional nitrogen-doped graphenic materials, which could be used as oxygen reduction catalysts in membrane fuel cells, a solvothermal-based route was successfully carried out. However, the solvothermal reaction between metallic sodium and 1-(2-hydroxyethyl)piperidine (HEP), with the latter as the source of both carbon and nitrogen, is still little understood. The present work was aimed at investigating the solvothermal process under different conditions of temperature and pressure and with different amounts of sodium. Use of in situ mass spectroscopy during the three-day reaction revealed the early formation of dihydrogen, as well as carbon oxides, methane and ammonia, in addition to fragments of ethylpiperidine alkoxide (EP-ONa). XRD measurements evidenced the formation of sodium-based compounds, e.g. hydride, carbonate, hydroxide, and cyanide. Interestingly, Raman spectroscopy revealed the significant presence of large aromatic molecules as well as an sp2 carbon network, an early precursor of graphene. Analysis of the overpressures and reaction yields suggests that the primary compound from the reaction of HEP with sodium is a large sp2 carbon-based network entrapping numerous sodium-based molecules as well as a volatile liquid phase. The suggested reaction mechanism provides information to better tailor the solvothermal products, whose pyrolysis at 850 °C led to very high specific area nitrogen-doped carbon materials. [ABSTRACT FROM AUTHOR]

The promising and extraordinary properties of graphene has attracted significant interest from many researchers especially in various electronic applications. The main aim of this work is to develop graphene-based ink with excellent stability and electrical properties for flexible electronics. Graphene foam (GF) was synthesised by using solvothermal method. GF exhibited multi layers of graphene, good in-plane crystallite quality, a low carbon impurity and relatively low sodium carbonate content. GF was further dispersed into various types of solvents. Results showed that GF dispersed in dimethyl sulfoxide (DMF) and N-methylpyrrolidone (NMP) exhibited good stability. However, these solvents suffer from highly toxic which may damage fertility or the unborn child (hazard code = H360). Besides that, GF dispersed in distilled water with an addition of sodium dodecyl sulfate (SDS) as a surfactant presented good stability as compared to GF ink without surfactant and can be further used as the conductive ink for printable electronics. [ABSTRACT FROM AUTHOR]

Graphene-based materials are extensively studied, due to their excellent properties and their wide range of possible applications. Attention has recently been paid to three-dimensional-like graphenic structures, such as crumpled graphene sheets and graphenic foams: these kinds of materials can combine the properties of graphene associating high surface area and porosity, what is particularly interesting for energy or catalysis applications. Most of the synthesis methods leading to such structures are based on graphite oxide exfoliation and re-assembly, but in this work we focus on the preparation of graphenic foams by a solvothermal-based process. We performed a solvothermal reaction between ethanol and sodium at 220°C, during 72 h, under 200 bar, followed by a pyrolysis under nitrogen flow. An extended study of the influence of the temperature (800°C-900°C) of pyrolysis evidences an unexpected strong effect of this parameter on the characteristics of the materials. The optimal conditions provide multi-layer graphene (10 layers) foam with a surface area of 2000 m2·g−1. This work is an important step for the understanding of the mechanisms of the thermal treatment. Post-treatments in different experimental conditions are performed in order to modulate the structure and properties of the graphenic foams. [ABSTRACT FROM AUTHOR]

Lignin is a potential renewable material for the production of bio-sourced aromatic chemicals. We present the first hydrotreatment of lignin pyrolysis vapors, before any condensation, using inexpensive and sustainable iron-silica (Fe/SiO2) and iron-activated carbon (Fe/AC) catalysts. Lignin pyrolysis was conducted in a tubular reactor and vapors were injected in a fixed bed of catalysts (673 K, 1 bar) with stacks to investigate the profile of coke deposit. More than 170 GC-analyzable compounds were identified by GCxGC (heart cutting)/flame ionization detector mass spectrometry. Lignin oligomers were analyzed by very high resolution mass spectrometry, called the 'petroleomic' method. They are trapped by the catalytic fixed bed and, in particular, by the AC. The catalysts showed a good selectivity for the hydrodeoxygenation of real lignin vapors to benzene, toluene, xylenes, phenol, cresols, and alkyl phenols. The spent catalysts were characterized by temperature-programmed oxidation, transmission electron microscopy (TEM), and N2 sorption. Micropores in the Fe/AC catalyst are completely plugged by coke deposits, whereas the mesoporous structure of Fe/SiO2 is unaffected. TEM images reveal two different types of coke deposit: 1) catalytic coke deposited in the vicinity of iron particles and 2) thermal coke (carbonaceous particles ≈1 μm in diameter) formed from the gas-phase growth of lignin oligomers. [ABSTRACT FROM AUTHOR]

Highlights: [•] Development of preparation procedure for mechanically stable half-cells. [•] Promising use of PSSA-grafted carbon support for PEM fuel cell cathodes. [•] Nafion addition in half-cells could be reduced by 50% by carbon modification. [•] Electrochemical characterization and resistance of half cells with modified carbon. [Copyright &y& Elsevier]

Abstract: Chromia forming alloys (stainless steels) are among the best candidates for SOFC interconnects. However, problems of decreasing electronic conductivity during high temperature service and volatility of chromium oxide scales need to be solved. Electronically conductive surface coatings, which also reduce oxide scale growth and chromium volatility, are needed to improve stainless steel interconnects. The goal of this study is to investigate combinations of lanthanum oxide (La2O3) and cobalt manganese oxide ((Co,Mn)3O4) coatings on Crofer22APU stainless steel. Thin film coatings of La2O3 (~200 nm) and Co,Mn (1:1) (~2 mm) were deposited via metal organic chemical vapor deposition and magnetron sputtering, respectively. Three types of coatings were investigated: La2O3; (Co,Mn)3O4 (formed by a 100 h, 800 °C air anneal of Co,Mn); and, a combination coating composed of an air annealed La2O3 followed by a (Co,Mn)3O4 layer. Oxidation experiments were performed at 800 °C in air for both 100 and 1000 h and in dual environment (Air+3%H2O/H2 +3%H2O) for 100 h. The combination coatings were observed to inhibit both the formation of chromia (compared to the single (Co,Mn)3O4 layer) and the formation of iron oxide in dual atmosphere (compared to the single La2O3). These and other results and interpretations are presented and discussed here. [Copyright &y& Elsevier]