S. V. Dubkov

The effect of gold on modern bimetallic Au–Cu/MWCNT catalysts for the oxy-steam reforming of methanol

Copper and gold doped copper catalysts supported on multi-walled carbon nanotubes were prepared by wet impregnation and deposition–precipitation methods, respectively. The catalysts were tested in the oxy-steam reforming of methanol (OSRM) and characterized by XRD, SEM-EDS, TOF-SIMS, thermo-gravimetric analysis and temperature-programmed desorption of ammonia. The reactivity results showed the promotion effect of gold on the activity and selectivity of the copper catalysts in the OSRM. The formed Cu–Au alloy as an active phase was responsible for the activity and selectivity improvement of the bimetallic catalysts in the oxy-steam reforming of methanol. The formation of an Au–Cu alloy was confirmed by the XRD, TOF-SIMS and SEM-EDS techniques. The reducibility and acidity of the tested catalysts are important factors, which influence the activity of the copper and gold–copper catalysts.

Use of thin film of a Co15Ti40N35 alloy for CVD catalytic growth of carbon nanotubes

It is shown that multiwalled carbon nanotubes can be grown on the catalytic surface of a Co–Ti–N alloy with low (~10 at %) cobalt content by the conventional method of chemical deposition from acetylene. Adding nitrogen to the composition of the Co–Ti contributes the formation of the TiN compound and extrusion of Co onto the surface where it makes a catalytic effect for CNT growth. It was found that the tubes begin growth at a temperature of 400°C. It is shown by studies using Raman spectroscopy that the quality of CNT improves with increasing temperature.

Formation of carbon nanotubes on an amorphous Ni25Ta58N17 alloy film by chemical vapor deposition

It is shown that it is possible to grow carbon nanotubes on the surface of an amorphous Ni–Ta–N metal alloy film with a low Ni content (~25 at %) by chemical deposition from acetylene at temperature 400–800°C. It is established that the addition of nitrogen into the Ni–Ta alloy composition is favorable for the formation of tantalum nitride and the expulsion of Ni clusters, which act as a catalyst of the growth of carbon nanotubes, onto the surface. From Raman spectroscopy studies, it is found that, as the temperature of synthesis is raised, the quality of nanotubes is improved.

Growth of vertically aligned multiwalled carbon nanotubes forests on metal alloy Ni-Nb-N with low content of catalyst

This research shows the possibility of carbon nanotubes (CNTs) formation on the surface of low nickel (~ 10 at.%) Ni-Nb-N amorphous metal alloy film by CVD method at 550 °C of the gas mixture based on acetylene. The structure of CNT were studied by transmission and scanning-electron microscopy, energy-dispersive X-ray and the Raman spectroscopy.

Fischer–Tropsch synthesis over various Fe/Al2O3–Cr2O3 catalysts

Monometallic iron supported catalysts were prepared by the impregnation method and tested in Fischer–Tropsch (F–T) synthesis. The activity tests performed in the studied reaction showed that the composition of the catalyst strongly influences the reactivity of the catalytic systems in the F–T reaction. It was also found that the system which showed the highest content of iron species on the catalyst surface exhibited the highest yield in F–T reaction. In addition, the most active catalyst also showed high specific surface area, high total acidity value and the highest amount of iron species on the catalyst surface. The analysis of the liquid product of F–T synthesis confirmed the occurrence of aliphatic, branched and unsaturated linear hydrocarbons.

Carbon Deposits Formed on the Surface of Ru–Ni Catalysts During the Mixed Reforming of Methane Process

Monometallic nickel and bimetallic ruthenium–nickel catalysts supported onto aluminum oxide without additives and aluminum oxide modified with MgO and CaO were prepared by an impregnation method. The catalysts were tested in the process of the mixed reforming of methane, and their properties were characterized by thermogravimetry, scanning electron microscopy, and X-ray diffractometry. The total organic carbon content of the catalysts was also measured. The promoting effect of ruthenium and structural promoters on the catalytic activity of Ni/Al2O3 was confirmed. The Ru–Ni/MgO–Al2O3 catalyst exhibited the highest stability and activity; this fact can be explained by the increased adsorption of methane on the surface of ruthenium–nickel clusters.

Supported Ru−Ni Catalysts for Biogas and Biohydrogen Conversion into Syngas

Catalytic properties of monometallic Ni and bimetallic Ru–Ni supported on Al2O3, CaO–Al2O3, and MgO–Al2O3 have been studied in mixed reforming of methane. Physicochemical properties of the catalytic systems have been studied by X-ray diffraction, scanning electron microscopy with energy dispersive spectroscope and temperature-programmed reduction by hydrogen. It has been shown that, of all the studied samples, the highest conversion of methane and carbon dioxide is achieved in the presence of the Ru−Ni/MgO–Al2O3 bimetallic catalyst. Temperature-programmed reduction has confirmed the effect of hydrogen spillower from ruthenium to NiO. The formation of Ru–Ni alloy has also been found.

Effect of electrolyte temperature on the cathodic deposition of Ge nanowires on in and Sn particles in aqueous solutions

The results of studying the growth of filamentous Ge structures in aqueous electrolytes at various temperatures using In and Sn nanoparticle arrays as nucleation sites are given. The temperature of Ge cathodic deposition process from aqueous solutions has a significant effect on the layer structure deposited onto the surface. In the presence of metal particles in the molten state, filamentous Ge structures grow due to the cathodic reduction of Ge-containing ions on the electrode surface, followed by dissolution and crystallization in the melt at the substrate interface. The results obtained show the crucial role of liquid metal particles during the electrochemical formation of germanium nanowires.

CVD-growth of CNT with the use of catalutic Ct–Me–N–O thin films incorporated in the technology

The process of the formation of carbon nanotube arrays on Ct–Me–N catalytic alloys of low nickel content (10–20 at %) by chemical vapor deposition, where Ct is a catalytic metal from the group of Ni, Co, Fe, and Pd, and Me is a transition metal of group IV–VII of the periodic table, was investigated. It is shown that CNT grow effectively when the alloy contains Ti, V, Cr, Zr, Hf, Nb, and Ta. The addition of nitrogen and oxygen to the alloy’s composition gives rise to a buildup of oxynitrides, expelling of the catalyst, and formation of its clusters on the surface. The replacement of metals in the alloy has an effect on the diameter of the CNT. Moreover, the alloy films 10–500 nm thick can be used for the CNT growth, which is responsible for high degree of homogeneity and the repeatability of the process. CNT growth was not observed when the alloy contained W and Re.

The features of CNT growth on catalyst-content amorphous alloy layer by CVD-method

This work is devoted to the CVD-synthesis of arrays of carbon nanotubes (CNTs) on Co-Zr-N-(O), Ni-Nb-N-(O), Co- Ta-N-(O) catalytic alloy films from gas mixture of C2H2+NH3+Ar at a substrate temperature of about 550°C.Heating of the amorphous alloy causes its crystallization and squeezing of the catalytic metal onto the surface. As a result, small catalyst particles are formed on the surface. The CNT growth takes place after wards on these particles. It should be noted that the growth of CNT arrays on these alloys is insensitive to the thickness of alloy film, which makes this approach technically attractive. In particular, the possibility of local CNT growth at the ends of the Co-Ta-N-(O) film and three-level CNT growth at the end of more complex structure SiO2/Ni-Nb-N-O/SiO2/Ni-Nb-N-O/SiO2/Ni-Nb-N-O/SiO2 is demonstrated.