Nitrogen-containing functional groups were generated on the surface of partially oxidized multi-walled carbon nanotubes (CNTs) via post-treatment in ammonia. The treatment temperature was varied in order to tune the amount and type of nitrogen- and oxygen-containing functional groups, which were studied using high-resolution X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). The surface defects on CNTs due to the incorporation of nitrogen were investigated by Raman spectroscopy. Deconvoluted XP N1s spectra were used for the quantification of different nitrogen-containing functional groups, and TPD studies were performed in inert and ammonia atmosphere to investigate the surface reactions occurring on the oxidized CNT surfaces quantitatively. Nitrile, lactam, imide and amine-type functional groups were formed in the presence of ammonia below 300 degrees C. When the OCNTs were treated in the medium temperature range between 300 degrees C to 500 degrees C, mainly pyridine-type nitrogen groups were generated, whereas pyridinic, pyrrolic and quaternary-type nitrogen groups were the dominating species present on the CNT surface when treated above 500 degrees C. It was found that about 38% of the oxygen functional groups react with ammonia below 500 degrees C.

Nanoscale palladium and nickel colloids prepared in the presence of certain tetra-n-octylammonium carboxylates contain a high proportion of nonequilibrium trigonal cross section particles. Specifically, those carboxylates which bear a hydroxy function at the R-position, e.g., tetra-n-octylammonium glycolate, exert a strong influence on the shape of the metal colloids. It is shown by an in situ FTIR study of the preparation of colloidal nickel from bis(cyclooctadiene)nickel in the presence of tetra-n-octylammonium glycolate that the interaction of the R-hydroxy carboxylate with the surface of the colloidal metal particle is likely to be the morphology-determining factor in the shape-selective preparation of these metal particles.

Co-precipitation of CuZn(Al) precursor materials is the traditional way of synthesizing Cu/ZnO/(Al2O3) catalysts for industrial methanol synthesis. This process has been investigated by titration experiments of nitrate and formate solutions. It was found that the solidification of the single components proceeds sequentially in case of nitrates: Cu 2+ is precipitated at pH 3 and Zn 2+ (as well as Al 3+ ) near pH 5. This behavior prevents a homogeneous distribution of all metal species in the initial precipitate upon gradual increase of pH and requires application of the constant pH micro-droplet method. This effect is less pronounced if formate instead of nitrate is used as counter ion. This can be explained by the strong modification of the hydrolysis chemistry of the metal ions due to the presence of formate anions, which act as ligands and buffer. A formate-derived Cu/ZnO/Al2O3 catalyst was more active in methanol synthesis compared to a nitrate-derived sample although the same crystallographic phases were present in the precursor after co-precipitation and ageing. The effect of precipitation temperature was studied for the binary CuZn nitrate model system. Increasing the temperature of co-precipitation above 50 °C leads to down-shift of the precipitation pH of Zn 2+ by a full unit. Thus, in warm solutions more acidic conditions can be used for complete co-precipitation, while in cold solutions, some Zn 2+ may remain dissolved in the mother liquor at the same precipitation pH. The higher limit of temperature is given by the tendency of the initial Cu precipitate towards formation of CuO by oxolation. On the basis of these considerations, the empirically determined optimal pH and temperature conditions of the industrially applied synthesis can be rationalized.

The activity of Cu/ZnO/Al2O3 catalysts for methanol synthesis is determined by the microstructural arrangement of the oxides among other factors. A large metal/oxide interface area seems to enhance the intrinsic activity of Cu. A novel type of Cu/ZnO/Al2O3 catalyst demonstrates the potential of this positive effect, which can outweigh the simultaneous loss of gas accessible Cu surface area in comparison to a conventionally prepared sample

The adsorption of carbon dioxide on differently pretreated polycrystalline ZnO was studied by thermodynamic and kinetic methods. The uptake of CO 2 observed in a static Tian-Calvet microcalorimeter reached saturation at about 5 µmol/m 2 , corresponding to about half of the exposed Zn 2+ sites after a thorough thermal pretreatment at 450 °C for 4 h. The saturation uptake was found to be correlated inversely with the amount of residual hydroxyl groups on the ZnO surfaces. At room temperature, the adsorption of CO 2 was found to occur in two steps. Initially, the adsorption was nonactivated, and the exposed surfaces were saturated at a very low equilibrium pressure (p , 1 Pa) with an initial differential heat of adsorption (q diff ) of 100-120 kJ/mol, a standard entropy of -190 J mol -1 K -1 , and an adsorption rate constant of 10 -5 Pa -1 s -1 . During the second stage, an inhibiting effect was observed; the equilibrium coverage increased slowly with increasing pressure, q diff decreased rapidly with increasing coverage, and the rate of adsorption was low. Temperature-programmed desorption measurements indicated the formation of strongly adsorbed polydentate carbonates at higher temperatures with an adsorption energy between 120 and 160 kJ/mol.