Hierarchically structured nanoporous carbon tubes for high pressure carbon dioxide adsorption

Mesoscopic, nanoporous carbon tubes were synthesized by a combination of the Stoeber process and the use of electrospun macrosized polystyrene fibres as structure directing templates. The obtained carbon tubes have a macroporous nature characterized by a thick wall structure and a high specific surface area of approximately 500 m²/g resulting from their micro- and mesopores. The micropore regime of the carbon tubes is composed of turbostratic graphitic areas observed in the microstructure. The employed templating process was also used for the synthesis of silicon carbide tubes. The characterization of all porous materials was performed by nitrogen adsorption at 77 K, Raman spectroscopy, infrared spectroscopy, thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM). The adsorption of carbon dioxide on the carbon tubes at 25 °C at pressures of up to 30 bar was studied using a volumetric method. At 26 bar, an adsorption capacity of 4.9 mmol/g was observed. This is comparable to the adsorption capacity of molecular sieves and vertically aligned carbon nanotubes. The high pressure adsorption process of CO2 was found to irreversibly change the microporous structure of the carbon tubes

Synthesis, characterization and p–n type gas sensing behaviour of CuFeO₂ delafossite type inorganic wires using Fe and Cu complexes as single source molecular precursors

CuFeO2 delafossite type nanowires with a diameter of 180 nm were successfully synthesized by electrospinning using an equimolar mixture of molecular copper and iron precursors and polyacrylnitrile as polymer template followed by calcination. This mixture was electrospun under ambient conditions. The copper and iron precursor complexes diaqua-bis[2-(methoxyimino)-propanato] M(II) (M = Cu, Fe) were fully characterized by spectroscopic and electrochemistry methods (NMR, IR, cyclovoltammetry) as well as by single crystal structure and by thermogravimetric analysis (TGA). The pre-ceramic electrospun composite fiber mats were subsequently heat treated in a two step procedure to yield the final CuFeO2 delafossite type nanowires agglomerated as microsized ceramic mats. Intermediate oxide phases as well as the finally obtained CuFeO2 fibrous mats composed of delafossite type nanowires were characterized analytically by temperature dependent powder X-ray crystallography (PXRD). Their topological morphology was studied by scanning electron microscopy (SEM). The obtained CuFeO2 fibrous mats were studied with respect to their O2 gas sensing behaviour and variable p and n-type semiconducting behaviour depending on temperature was observed