Carbon structure-controlled syntheses

Many ORR experiments have been made on electrocatalysts composed by Pt and Pd with the addition of non-noble metals, such as Co, Fe, and Ni. However, under electrochemical conditions these non-noble metals might leach out from the electrocatalyst, as demonstrated in previous investigations [25]. In order to avoid this problem, Yang and co-authors [26] have investigated PdPt-based electrocatalysts for the ORR in absence and in the presence of methanol, because the long-term stability of Pd in acidic solution is comparable to that of Pt (but this depends on the potential - additionally, Pt may stabilize Pd atoms in the alloy). It was report a novel strategy for surface and structure-controlled synthesis of carbon-supported Pd3Pti nanoparticles for the ORR as well as for methanol-tolerant ORR electrocatalyst. The influence of the surface composition and structure of the PdsPti/C on the ORR activity in the absence and presence of methanol was also reported. 

Abstract Synthesis of carbon adsorbents with controlled pore size and surface chemistry adapted for application in medicine and health protection was explored. Conjugated polymers were used as carbon precursors. These polymers with conjugated double bonds C = C have high thermal stability. Formation of sp carbon structures occurs via condensation and aromatization of macromolecules. The structure of carbon materials obtained is related to the structure of the original conjugated polymer, thus the porous structure of carbon adsorbents could be controlled by variation of the conjugated polymer precursor. 

Jacob, M., Palmqvist, U., Alberius, P.C.A., Ekstrom, T., Nygren, M., and Lidin, S. Synthesis of structurally controlled nanocarbons—in particular the nanobarrel carbon. Solid State Sci. 5, 2003 133-137. 

It has been found experimentally that polystyrene solutions promise much as carbonization precursors for the synthesis of carbon nanostructures in porous composites-matrices. Using polystyrene solutions, one can control the size and shape of the carbon structures formed by changing the conformation of PS macromolecules and interaction with composite-matrix structure elements ... 

More industrial polyethylene copolymers were modeled using the same method of ADMET polymerization followed by hydrogenation using catalyst residue. Copolymers of ethylene-styrene, ethylene-vinyl chloride, and ethylene-acrylate were prepared to examine the effect of incorporation of available vinyl monomer feed stocks into polyethylene [81]. Previously prepared ADMET model copolymers include ethylene-co-carbon monoxide, ethylene-co-carbon dioxide, and ethylene-co-vinyl alcohol [82,83]. In most cases,these copolymers are unattainable by traditional chain polymerization chemistry, but a recent report has revealed a highly active Ni catalyst that can successfully copolymerize ethylene with some functionalized monomers [84]. Although catalyst advances are proving more and more useful in novel polymer synthesis, poor structure control and reactivity ratio considerations are still problematic in chain polymerization chemistry. 

The silica materials with various pore-wall thicknesses are suitable as templates for mesoporous carbons with controlled pore diameters.[252] The carbons exhibit wide varieties of pore shape, connectivity, and pore-wall thickness, depending on the silica templates that are synthesized with various structures and pore diameters. The syntheses of mesoporous carbons are summarized in Table 8.8. Figure 8.49 show the XRD pattern of CMK-3 (keeps original symmetry) [34] and Figure 8.50 shows the changes in powder XRD patterns during synthesis of the CMK-1 with its silica template MCM-48 (creates new symmetry).1321... 

Carbon nanostructures display a wide variety of extraordinary properties that greatly depend on their structure. Combined with their small size, these properties can result in devices and emerging applications that have not been possible previously. Advances in controlled synthesis, separation, and characterization of these nanostructures are making possible the reproducible manufacture of carbon nanomaterials with tuned structure for specific applications. Carbon nanostructures may impact diverse fields that range from electronics to materials and biomedical applications. 

Jacob, M. et aL Synthesis of structurally controlled nanocarbons—In particular the nanobarrel carbon. Solid State Sciences 5, 133-137, 2003. 

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