Andrey Stadnichenko - Academia.edu (original) (raw)
Papers by Andrey Stadnichenko
The Journal of Physical Chemistry C, 2015
Carbon, 2015
Highly uniform and crystalline ultradisperse Pt nanoparticles with average sizes of 2.4 nm were d... more Highly uniform and crystalline ultradisperse Pt nanoparticles with average sizes of 2.4 nm were deposited on oxygen-free few-layer graphene (FLG) by polyol reduction method without any additional protective agents. The samples were analyzed by Raman spectroscopy, photoelectron spectroscopy using synchrotron radiation and high-resolution transmission electron microscopy. The experiments showed that metal nanoparticles were mostly stabilized at defect sites of the FLG support in the absence of oxygen functionalities. Catalytic properties of the samples were tested in CO oxidation reaction. For Pt nanoparticles forming agglomerates an oscillatory behavior under catalytic reaction conditions was observed for the first time for metal-graphene catalysts. (E.D. Grayfer), fed@niic.nsc.ru (V.E. Fedorov). C A R B O N 8 9 ( 2 0 1 5 ) 2 9 0 -2 9 9
Surface Engineering, 2015
Moscow University Chemistry Bulletin, 2007
Gold oxide films obtained on the surface of polycrystalline gold foil upon oxidation by oxygen ac... more Gold oxide films obtained on the surface of polycrystalline gold foil upon oxidation by oxygen activated by a high-frequency discharge have been studied by X-ray photoelectron spectroscopy. High-frequency O 2 activation affords oxide films more than 3-5 nm thick. As follows from Au4 f spectra, the surface gold atoms are oxidized to the oxidation state +3. The O1 s spectra have a composite shape and are decomposed into four components that characterize nonequivalent states of oxygen in the resulting oxide films. It is assumed that the two major oxygen states ( E b (O1 s ) = 529.0 and 530.0 eV) correspond to the oxygen atoms in two-and threedimensional gold oxide Au 2 O 3 , respectively. The oxygen states characterized by the higher binding energies ( E b (O1 s ) = 531.8 and 535.2 eV) likely correspond to molecular oxygen in peroxide and superoxide groups, respectively.
Chinese Journal of Catalysis, 2014
The nanocomposites based on cobalt oxide and nitrogen-doped carbon nanofibers (N-CNFs) with cobal... more The nanocomposites based on cobalt oxide and nitrogen-doped carbon nanofibers (N-CNFs) with cobalt oxide contents of 10-90 wt% were examined as catalysts in the CO oxidation and supercapacity electrodes. Depending on Со3О4 content, such nanocomposites have different morphologies of cobalt oxide nanoparticles, distributions over the bulk, and ratios of Со 3+ /Co 2+ cations. The 90%Со3О4-N-CNFs nanocomposite showed the best activity because of the increased concentration of defects in N-CNFs. The capacitance of electrodes containing 10%Со3О4-N-CNFs was 95 F/g, which is 1.7 times higher than electrodes made from N-CNFs.
Journal of Nanotechnology, 2012
We present the simple procedure of the vapor-phase bromination of multiwall carbon nanotubes (MWN... more We present the simple procedure of the vapor-phase bromination of multiwall carbon nanotubes (MWNTs) at moderate temperatures. MWNTs with average diameter 9 ± 3 nm were treated with Br 2 vapors at 250 • C to produce Br-functionalized product. Transmission electron microscopy analysis was used to prove low damage of MWNT walls during bromination. X-ray photoelectron spectroscopy (XPS) and differential thermal analysis (DTA) were used to investigate chemical composition of the surface of initial and brominated nanotubes. The experimental results show that the structure of MWNTs is not affected by the bromination process and the total amount of Br-containing surface functions reaches 2.5 wt. %. Electrophysical properties of initial and brominated MWNTs were investigated showing decrease of conductivity for functionalized sample. Possible mechanism of the vapor-phase bromination via surface defects and oxygen-containing functional groups was proposed according to data obtained. Additional experiments with bromination of annealed low-defected MWNTs were performed giving Br content a low as 0.75 wt. % proving this hypothesis.
The Journal of Physical Chemistry C, 2012
Oxidized palladium nanoparticles, PdO x (x ≈ 1.3), measuring approximately 3 nm in size were prep... more Oxidized palladium nanoparticles, PdO x (x ≈ 1.3), measuring approximately 3 nm in size were prepared by RF-discharge under an oxygen atmosphere. The Pd3d X-ray photoelectron spectra (XPS) of oxidized palladium nanoparticles show two main peaks with binding energy E b (Pd3d 5/2 ) at ∼336.5 and 338.6 eV, which were assigned to Pd 2+ and Pd 4+ species, respectively. Attempts to synthesize pure Pd 4+ nanoparticles by plasma treatment without the presence of Pd 2+ were unsuccessful. High-resolution transmission electron microscopy (HRTEM) data show the defect structure of the palladium nanoparticles. The particles' thermal stability is relatively high, being stable up to ∼425−450 K. The oxidized palladium species (Pd 4+ ) were found to be highly reactive toward CO at room temperature. These results demonstrate the necessity of further investigation of highly oxidized palladium species as possible active centers in CO oxidation reactions.
Surface Science, 2006
... CO adsorption on the Au/carbon systems was very similar to that observed for various Au/oxide... more ... CO adsorption on the Au/carbon systems was very similar to that observed for various Au/oxide systems previously studied. This finding strongly indicates that CO adsorption on gold is essentially independent of the nature of support. ...
Colloid Journal, 2000
Constitution and dispersity of the products of thermal decomposition of silver nitrate ammonia co... more Constitution and dispersity of the products of thermal decomposition of silver nitrate ammonia complex sorbed by polyacrylate matrix are studied by the methods of small- and wide-angle X-ray scattering, optical, photoelectron and Auger-electron spectroscopies. It is shown that, at temperatures of 140–150°C, the complete decomposition of the complex occurs with the formation of nanoparticles and charged silver clusters in polymer
Kinetics and Catalysis, 2013
ABSTRACT Oxidized copper clusters 2–5 nm in size have been obtained by RF discharge sputtering of... more ABSTRACT Oxidized copper clusters 2–5 nm in size have been obtained by RF discharge sputtering of a copper wire in an oxygen atmosphere. Isolated CuO clusters or, at long deposition times, their agglomerates form on the support. The thermal stability of the oxidized nanoparticles in a vacuum and their reactivity toward CO in relation to the deposition time have been investigated by X-ray photoelectron spectroscopy. The asprepared clusters show low reactivity (10−7−10−9), but their activation by reduction and subsequent reoxidation in an oxygen medium raises their reactivity to ∼10−5. This is due to the appearance of weakly charged oxygen species on the surface. The reactivity of the CuO clusters has been compared to the reactivity of earlier studied nanosized copper oxide model objects.
Kinetics and Catalysis, 2010
It was studied the influence of gold addition on physico-chemical properties and catalytic activi... more It was studied the influence of gold addition on physico-chemical properties and catalytic activity of bimetallic Ni-Au/Al2O3 catalyst in partial oxidation of methane (POM). The reduction behavior in hydrogen, XRD crystal structure, XPS spectra and POM catalytic activity were investigated. The reduction of Ni-Au catalyst is a prerequisite condition to catalyze POM reaction. The formation of Ni-Au alloy during high
Kinetics and Catalysis, 2007
ABSTRACT The copper-cerium oxide catalysts were characterized using a set of physicochemical tech... more ABSTRACT The copper-cerium oxide catalysts were characterized using a set of physicochemical techniques including in situ FTIR spectroscopy, XPS, and XRD. It was found that copper segregated on the surface of cerium oxide and its states were labile and dependent on catalyst pretreatment conditions. Copper in a dispersed state was responsible for the reaction of CO oxidation in the presence of H2 on the copper-cerium oxide catalysts. It is likely that this state of copper was composed of two-dimensional or three-dimensional surface clusters containing Cu+ ions.
Journal of Structural Chemistry, 2008
A Cu 1 O 1.7 oxide film containing a large amout of superstoichiometric oxygen was obtained by lo... more A Cu 1 O 1.7 oxide film containing a large amout of superstoichiometric oxygen was obtained by lowtemperature oxidation of metallic copper in the oxygen plasma. An STM study of the film structure showed that ~10 nm planar copper oxide nanocrystallites with particles packed parallel to the starting metal surface. In an XPS study, the spectral characteristics of the Cu2p and O1s lines indicated that particles with a CuO lattice formed (E bnd (Cu2p 3/2 ) = 933.3 eV and a shake-up satellite, E bnd (O1s) = 529.3 eV). The additional superstoichiometric oxygen is localized at the sites of contact of nanoparticles in the interunit space and is characterized by a state with the binding energy E bnd (O1s) = 531.2 eV. Due to the formation of a nanostructure in the films during low-temperature plasma oxidation, the resulting copper oxide has a much lower thermal stability than crystalline oxide CuO.
Journal of Molecular Catalysis A: Chemical, 2013
CuO nanopowders were prepared by precipitation from alkaline solutions and were studied by TPR-CO... more CuO nanopowders were prepared by precipitation from alkaline solutions and were studied by TPR-CO + O 2 , XRD, TGA, TPD-He and XPS. All of the precipitated samples were characterized by excellent catalytic properties toward the low-temperature (LT) oxidation of CO with similar T 50 values of 110 • C. In contrast, bulk CuO oxides with sizes greater than 450 nm exhibited no activity at low temperatures. Several monolayers of chemisorbed species, such as water/hydroxyls and carbonate/hydrocarbonates, were typically observed at the surface of the nanopowders. These species were not critical for the LT oxidation of CO, and their preliminary removal did not substantially change the activity of the nanopowders. XPS results indicated a high deficiency of the oxygen sublattice of the CuO 1−x (x = 0.1-0.15) nanopowders, whereas, for the lattice of bulk CuO, the Cu/O ratio was 1. The highly deficient oxygen sublattice resulted in a disproportionation process, which, in turn, resulted in two observed oxygen forms. An oxygen form with E b (O1s) = 531.3 eV that is highly reactive toward CO was proposed to be responsible for the high catalytic activity of the CuO nanopowders. Slight differences in the Cu2p shake-up satellite structures were observed between the bulk and nanosized samples, which indicated that the electronic structure in the cationic sublattice had changed.
Fullerenes, Nanotubes and Carbon Nanostructures, 2006
Abstract The results of study of the surface chemistry of nanodiamonds treated by a mixture of HC... more Abstract The results of study of the surface chemistry of nanodiamonds treated by a mixture of HClO4 and H2SO2 acids are presented. Changes of the composition of surface diamond groups brought up by thermal annealing were monitored by Fourier transformed infrared spectroscopy and temperature‐programmed desorption. The decomposition of oxygen‐containing groups is observed at 300–900° C; CHx groups decompose at 700–1150° C. The process of the annealing of ND was investigated by the X‐ray photoelectron spectroscopy. ...
Chemical Engineering Science, 2012
The paper presents the experimental study and mathematical modeling of self-sustained oscillation... more The paper presents the experimental study and mathematical modeling of self-sustained oscillations in the reaction of CO oxidation on PdO/Al 2 O 3 catalysts. In experiments we observe the complicated multipeak oscillatory behavior of CO conversion under isothermal conditions. At these, the palladium surface is composed of a mixture of the metallic and oxide phases. We develop some new mathematical models describing the interaction of reagents with the Pd and PdO surfaces and taking into account the influence of the reaction medium on the catalyst activity. The models qualitatively describe the relaxation and multi-peak oscillations of the CO conversion. The redox process of Pd-PdO transition observed in the experiment causes the relaxation oscillations, while the mixed-mode oscillations in the model are observed due to coupling between the deep oxidation of palladium and the surface modification by oxygen. (E.A. Lashina). Please cite this article as: Lashina, E.A., et al., Self-sustained oscillations in CO oxidation reaction on PdO/Al 2 O 3 catalyst. Chem. Eng. Sci. (2012), http://dx.
Applied Surface Science, 2011
Nanostructured copper (II) oxide was formed on clean copper foil at room temperature using activa... more Nanostructured copper (II) oxide was formed on clean copper foil at room temperature using activated oxygen produced by RF discharge. CuO particles of approximately 10-20 nm were observed on the surface by Scanning Tunneling Microscopy (STM). The copper states and oxygen species of the model cupric oxide were studied by means of X-ray Photoelectron Spectroscopy (XPS). These oxide particles demonstrated abnormally high reactivity with carbon monoxide (CO) at temperatures below 100 • C. The XPS data showed that the interaction of CO with the nanostructured cupric oxide resulted in reduction of the CuO particles to Cu 2 O species. The reactivity of the nanostructured cupric oxide to CO was studied at 80 • C using XPS in step-by-step mode. The initial reactivity was estimated to be 5 × 10 −5 and was steadily reduced down to 5 × 10 −9 as the exposure was increased. O1s spectral analysis allowed us to propose that the high initial reactivity was caused by the presence of non-lattice oxygen states on the surface of the nanostructured CuO. We established that reoxidation of the partially reduced nanostructured cupric oxide by molecular oxygen O 2 restored the highly reactive oxygen form on the surface. These results allowed us to propose that the nanostructured cupric oxide could be used for low temperature catalytic CO oxidation. Some hypotheses concerning the nature of the non-lattice oxygen species with high reactivity are also discussed.
Applied Surface Science, 2012
Multiwall carbon nanotubes (MWNT) with three medium diameters (20-22, 9-13, and 6-8 nm) and diffe... more Multiwall carbon nanotubes (MWNT) with three medium diameters (20-22, 9-13, and 6-8 nm) and different morphology were chemically oxidized using concentrated nitric acid, mixture of nitric and sulfuric acids ("mélange" solution) and mixture of sulfuric acid and hydrogen peroxide ("piranha" solution). Influence of MWNT type and structure as well as type of oxidizer on the surface composition and structure of nanotubes after oxidation was investigated. Acid-base titration, X-ray photoelectron spectroscopy and thermal gravimetric analysis were used for quantitative and qualitative investigation of surface group composition of initial and oxidized nanotubes. Amount of oxygen-containing groups on the surface of oxidized MWNT depends on the type of initial MWNT. It was found that ratio of different oxygen containing groups is less dependent on the type of oxidizer. Electrophysical properties of initial and oxidized nanotubes were investigated in temperature range 4-293 K and main types of electrical conductivity were determined. It was shown that oxidation results in decrease in electrical conductivity of all samples with simultaneous change in the conductivity mechanism. Dispersive behavior of initial and oxidized nanotubes in different commonly used solvents was investigated. It was shown that oxidation leads to the improvement of sedimentation stability of MWNT in polar solvents.
Applied Surface Science, 2010
The investigation of oxidized silver nanoparticles by the photoemission (XPS, UPS) and HRTEM meth... more The investigation of oxidized silver nanoparticles by the photoemission (XPS, UPS) and HRTEM methods was performed. The nanoparticles of oxidized silver were obtained in the vacuum chamber by two methods of synthesis: thermal evaporation of silver nanoparticles followed by transferring in convective gas flow and sputtering of oxidized clusters under the action of plasma. Both methods indicated that oxygen interaction with silver nanoparticles depends strongly on its size. It was shown that the chemical bonding of oxygen species stabilized on small particles differs from the oxygen species adsorbed on bulk silver surfaces (monocrystals, foils and large particles). The low charged oxygen with molecular type of bonding stabilizes on particles of size approximately 5 nm and smaller. Increasing particle size leads to the dissociation of molecular oxygen species and the formation of strongly charged oxygen composed of oxide nanoparticles like Ag 2 O or AgO type. The presence of extended defects in the microdomain large nanoparticles facilitates the formation of Ag 2 O or AgO layers covering metallic nanosilver.
The Journal of Physical Chemistry C, 2015
Carbon, 2015
Highly uniform and crystalline ultradisperse Pt nanoparticles with average sizes of 2.4 nm were d... more Highly uniform and crystalline ultradisperse Pt nanoparticles with average sizes of 2.4 nm were deposited on oxygen-free few-layer graphene (FLG) by polyol reduction method without any additional protective agents. The samples were analyzed by Raman spectroscopy, photoelectron spectroscopy using synchrotron radiation and high-resolution transmission electron microscopy. The experiments showed that metal nanoparticles were mostly stabilized at defect sites of the FLG support in the absence of oxygen functionalities. Catalytic properties of the samples were tested in CO oxidation reaction. For Pt nanoparticles forming agglomerates an oscillatory behavior under catalytic reaction conditions was observed for the first time for metal-graphene catalysts. (E.D. Grayfer), fed@niic.nsc.ru (V.E. Fedorov). C A R B O N 8 9 ( 2 0 1 5 ) 2 9 0 -2 9 9
Surface Engineering, 2015
Moscow University Chemistry Bulletin, 2007
Gold oxide films obtained on the surface of polycrystalline gold foil upon oxidation by oxygen ac... more Gold oxide films obtained on the surface of polycrystalline gold foil upon oxidation by oxygen activated by a high-frequency discharge have been studied by X-ray photoelectron spectroscopy. High-frequency O 2 activation affords oxide films more than 3-5 nm thick. As follows from Au4 f spectra, the surface gold atoms are oxidized to the oxidation state +3. The O1 s spectra have a composite shape and are decomposed into four components that characterize nonequivalent states of oxygen in the resulting oxide films. It is assumed that the two major oxygen states ( E b (O1 s ) = 529.0 and 530.0 eV) correspond to the oxygen atoms in two-and threedimensional gold oxide Au 2 O 3 , respectively. The oxygen states characterized by the higher binding energies ( E b (O1 s ) = 531.8 and 535.2 eV) likely correspond to molecular oxygen in peroxide and superoxide groups, respectively.
Chinese Journal of Catalysis, 2014
The nanocomposites based on cobalt oxide and nitrogen-doped carbon nanofibers (N-CNFs) with cobal... more The nanocomposites based on cobalt oxide and nitrogen-doped carbon nanofibers (N-CNFs) with cobalt oxide contents of 10-90 wt% were examined as catalysts in the CO oxidation and supercapacity electrodes. Depending on Со3О4 content, such nanocomposites have different morphologies of cobalt oxide nanoparticles, distributions over the bulk, and ratios of Со 3+ /Co 2+ cations. The 90%Со3О4-N-CNFs nanocomposite showed the best activity because of the increased concentration of defects in N-CNFs. The capacitance of electrodes containing 10%Со3О4-N-CNFs was 95 F/g, which is 1.7 times higher than electrodes made from N-CNFs.
Journal of Nanotechnology, 2012
We present the simple procedure of the vapor-phase bromination of multiwall carbon nanotubes (MWN... more We present the simple procedure of the vapor-phase bromination of multiwall carbon nanotubes (MWNTs) at moderate temperatures. MWNTs with average diameter 9 ± 3 nm were treated with Br 2 vapors at 250 • C to produce Br-functionalized product. Transmission electron microscopy analysis was used to prove low damage of MWNT walls during bromination. X-ray photoelectron spectroscopy (XPS) and differential thermal analysis (DTA) were used to investigate chemical composition of the surface of initial and brominated nanotubes. The experimental results show that the structure of MWNTs is not affected by the bromination process and the total amount of Br-containing surface functions reaches 2.5 wt. %. Electrophysical properties of initial and brominated MWNTs were investigated showing decrease of conductivity for functionalized sample. Possible mechanism of the vapor-phase bromination via surface defects and oxygen-containing functional groups was proposed according to data obtained. Additional experiments with bromination of annealed low-defected MWNTs were performed giving Br content a low as 0.75 wt. % proving this hypothesis.
The Journal of Physical Chemistry C, 2012
Oxidized palladium nanoparticles, PdO x (x ≈ 1.3), measuring approximately 3 nm in size were prep... more Oxidized palladium nanoparticles, PdO x (x ≈ 1.3), measuring approximately 3 nm in size were prepared by RF-discharge under an oxygen atmosphere. The Pd3d X-ray photoelectron spectra (XPS) of oxidized palladium nanoparticles show two main peaks with binding energy E b (Pd3d 5/2 ) at ∼336.5 and 338.6 eV, which were assigned to Pd 2+ and Pd 4+ species, respectively. Attempts to synthesize pure Pd 4+ nanoparticles by plasma treatment without the presence of Pd 2+ were unsuccessful. High-resolution transmission electron microscopy (HRTEM) data show the defect structure of the palladium nanoparticles. The particles' thermal stability is relatively high, being stable up to ∼425−450 K. The oxidized palladium species (Pd 4+ ) were found to be highly reactive toward CO at room temperature. These results demonstrate the necessity of further investigation of highly oxidized palladium species as possible active centers in CO oxidation reactions.
Surface Science, 2006
... CO adsorption on the Au/carbon systems was very similar to that observed for various Au/oxide... more ... CO adsorption on the Au/carbon systems was very similar to that observed for various Au/oxide systems previously studied. This finding strongly indicates that CO adsorption on gold is essentially independent of the nature of support. ...
Colloid Journal, 2000
Constitution and dispersity of the products of thermal decomposition of silver nitrate ammonia co... more Constitution and dispersity of the products of thermal decomposition of silver nitrate ammonia complex sorbed by polyacrylate matrix are studied by the methods of small- and wide-angle X-ray scattering, optical, photoelectron and Auger-electron spectroscopies. It is shown that, at temperatures of 140–150°C, the complete decomposition of the complex occurs with the formation of nanoparticles and charged silver clusters in polymer
Kinetics and Catalysis, 2013
ABSTRACT Oxidized copper clusters 2–5 nm in size have been obtained by RF discharge sputtering of... more ABSTRACT Oxidized copper clusters 2–5 nm in size have been obtained by RF discharge sputtering of a copper wire in an oxygen atmosphere. Isolated CuO clusters or, at long deposition times, their agglomerates form on the support. The thermal stability of the oxidized nanoparticles in a vacuum and their reactivity toward CO in relation to the deposition time have been investigated by X-ray photoelectron spectroscopy. The asprepared clusters show low reactivity (10−7−10−9), but their activation by reduction and subsequent reoxidation in an oxygen medium raises their reactivity to ∼10−5. This is due to the appearance of weakly charged oxygen species on the surface. The reactivity of the CuO clusters has been compared to the reactivity of earlier studied nanosized copper oxide model objects.
Kinetics and Catalysis, 2010
It was studied the influence of gold addition on physico-chemical properties and catalytic activi... more It was studied the influence of gold addition on physico-chemical properties and catalytic activity of bimetallic Ni-Au/Al2O3 catalyst in partial oxidation of methane (POM). The reduction behavior in hydrogen, XRD crystal structure, XPS spectra and POM catalytic activity were investigated. The reduction of Ni-Au catalyst is a prerequisite condition to catalyze POM reaction. The formation of Ni-Au alloy during high
Kinetics and Catalysis, 2007
ABSTRACT The copper-cerium oxide catalysts were characterized using a set of physicochemical tech... more ABSTRACT The copper-cerium oxide catalysts were characterized using a set of physicochemical techniques including in situ FTIR spectroscopy, XPS, and XRD. It was found that copper segregated on the surface of cerium oxide and its states were labile and dependent on catalyst pretreatment conditions. Copper in a dispersed state was responsible for the reaction of CO oxidation in the presence of H2 on the copper-cerium oxide catalysts. It is likely that this state of copper was composed of two-dimensional or three-dimensional surface clusters containing Cu+ ions.
Journal of Structural Chemistry, 2008
A Cu 1 O 1.7 oxide film containing a large amout of superstoichiometric oxygen was obtained by lo... more A Cu 1 O 1.7 oxide film containing a large amout of superstoichiometric oxygen was obtained by lowtemperature oxidation of metallic copper in the oxygen plasma. An STM study of the film structure showed that ~10 nm planar copper oxide nanocrystallites with particles packed parallel to the starting metal surface. In an XPS study, the spectral characteristics of the Cu2p and O1s lines indicated that particles with a CuO lattice formed (E bnd (Cu2p 3/2 ) = 933.3 eV and a shake-up satellite, E bnd (O1s) = 529.3 eV). The additional superstoichiometric oxygen is localized at the sites of contact of nanoparticles in the interunit space and is characterized by a state with the binding energy E bnd (O1s) = 531.2 eV. Due to the formation of a nanostructure in the films during low-temperature plasma oxidation, the resulting copper oxide has a much lower thermal stability than crystalline oxide CuO.
Journal of Molecular Catalysis A: Chemical, 2013
CuO nanopowders were prepared by precipitation from alkaline solutions and were studied by TPR-CO... more CuO nanopowders were prepared by precipitation from alkaline solutions and were studied by TPR-CO + O 2 , XRD, TGA, TPD-He and XPS. All of the precipitated samples were characterized by excellent catalytic properties toward the low-temperature (LT) oxidation of CO with similar T 50 values of 110 • C. In contrast, bulk CuO oxides with sizes greater than 450 nm exhibited no activity at low temperatures. Several monolayers of chemisorbed species, such as water/hydroxyls and carbonate/hydrocarbonates, were typically observed at the surface of the nanopowders. These species were not critical for the LT oxidation of CO, and their preliminary removal did not substantially change the activity of the nanopowders. XPS results indicated a high deficiency of the oxygen sublattice of the CuO 1−x (x = 0.1-0.15) nanopowders, whereas, for the lattice of bulk CuO, the Cu/O ratio was 1. The highly deficient oxygen sublattice resulted in a disproportionation process, which, in turn, resulted in two observed oxygen forms. An oxygen form with E b (O1s) = 531.3 eV that is highly reactive toward CO was proposed to be responsible for the high catalytic activity of the CuO nanopowders. Slight differences in the Cu2p shake-up satellite structures were observed between the bulk and nanosized samples, which indicated that the electronic structure in the cationic sublattice had changed.
Fullerenes, Nanotubes and Carbon Nanostructures, 2006
Abstract The results of study of the surface chemistry of nanodiamonds treated by a mixture of HC... more Abstract The results of study of the surface chemistry of nanodiamonds treated by a mixture of HClO4 and H2SO2 acids are presented. Changes of the composition of surface diamond groups brought up by thermal annealing were monitored by Fourier transformed infrared spectroscopy and temperature‐programmed desorption. The decomposition of oxygen‐containing groups is observed at 300–900° C; CHx groups decompose at 700–1150° C. The process of the annealing of ND was investigated by the X‐ray photoelectron spectroscopy. ...
Chemical Engineering Science, 2012
The paper presents the experimental study and mathematical modeling of self-sustained oscillation... more The paper presents the experimental study and mathematical modeling of self-sustained oscillations in the reaction of CO oxidation on PdO/Al 2 O 3 catalysts. In experiments we observe the complicated multipeak oscillatory behavior of CO conversion under isothermal conditions. At these, the palladium surface is composed of a mixture of the metallic and oxide phases. We develop some new mathematical models describing the interaction of reagents with the Pd and PdO surfaces and taking into account the influence of the reaction medium on the catalyst activity. The models qualitatively describe the relaxation and multi-peak oscillations of the CO conversion. The redox process of Pd-PdO transition observed in the experiment causes the relaxation oscillations, while the mixed-mode oscillations in the model are observed due to coupling between the deep oxidation of palladium and the surface modification by oxygen. (E.A. Lashina). Please cite this article as: Lashina, E.A., et al., Self-sustained oscillations in CO oxidation reaction on PdO/Al 2 O 3 catalyst. Chem. Eng. Sci. (2012), http://dx.
Applied Surface Science, 2011
Nanostructured copper (II) oxide was formed on clean copper foil at room temperature using activa... more Nanostructured copper (II) oxide was formed on clean copper foil at room temperature using activated oxygen produced by RF discharge. CuO particles of approximately 10-20 nm were observed on the surface by Scanning Tunneling Microscopy (STM). The copper states and oxygen species of the model cupric oxide were studied by means of X-ray Photoelectron Spectroscopy (XPS). These oxide particles demonstrated abnormally high reactivity with carbon monoxide (CO) at temperatures below 100 • C. The XPS data showed that the interaction of CO with the nanostructured cupric oxide resulted in reduction of the CuO particles to Cu 2 O species. The reactivity of the nanostructured cupric oxide to CO was studied at 80 • C using XPS in step-by-step mode. The initial reactivity was estimated to be 5 × 10 −5 and was steadily reduced down to 5 × 10 −9 as the exposure was increased. O1s spectral analysis allowed us to propose that the high initial reactivity was caused by the presence of non-lattice oxygen states on the surface of the nanostructured CuO. We established that reoxidation of the partially reduced nanostructured cupric oxide by molecular oxygen O 2 restored the highly reactive oxygen form on the surface. These results allowed us to propose that the nanostructured cupric oxide could be used for low temperature catalytic CO oxidation. Some hypotheses concerning the nature of the non-lattice oxygen species with high reactivity are also discussed.
Applied Surface Science, 2012
Multiwall carbon nanotubes (MWNT) with three medium diameters (20-22, 9-13, and 6-8 nm) and diffe... more Multiwall carbon nanotubes (MWNT) with three medium diameters (20-22, 9-13, and 6-8 nm) and different morphology were chemically oxidized using concentrated nitric acid, mixture of nitric and sulfuric acids ("mélange" solution) and mixture of sulfuric acid and hydrogen peroxide ("piranha" solution). Influence of MWNT type and structure as well as type of oxidizer on the surface composition and structure of nanotubes after oxidation was investigated. Acid-base titration, X-ray photoelectron spectroscopy and thermal gravimetric analysis were used for quantitative and qualitative investigation of surface group composition of initial and oxidized nanotubes. Amount of oxygen-containing groups on the surface of oxidized MWNT depends on the type of initial MWNT. It was found that ratio of different oxygen containing groups is less dependent on the type of oxidizer. Electrophysical properties of initial and oxidized nanotubes were investigated in temperature range 4-293 K and main types of electrical conductivity were determined. It was shown that oxidation results in decrease in electrical conductivity of all samples with simultaneous change in the conductivity mechanism. Dispersive behavior of initial and oxidized nanotubes in different commonly used solvents was investigated. It was shown that oxidation leads to the improvement of sedimentation stability of MWNT in polar solvents.
Applied Surface Science, 2010
The investigation of oxidized silver nanoparticles by the photoemission (XPS, UPS) and HRTEM meth... more The investigation of oxidized silver nanoparticles by the photoemission (XPS, UPS) and HRTEM methods was performed. The nanoparticles of oxidized silver were obtained in the vacuum chamber by two methods of synthesis: thermal evaporation of silver nanoparticles followed by transferring in convective gas flow and sputtering of oxidized clusters under the action of plasma. Both methods indicated that oxygen interaction with silver nanoparticles depends strongly on its size. It was shown that the chemical bonding of oxygen species stabilized on small particles differs from the oxygen species adsorbed on bulk silver surfaces (monocrystals, foils and large particles). The low charged oxygen with molecular type of bonding stabilizes on particles of size approximately 5 nm and smaller. Increasing particle size leads to the dissociation of molecular oxygen species and the formation of strongly charged oxygen composed of oxide nanoparticles like Ag 2 O or AgO type. The presence of extended defects in the microdomain large nanoparticles facilitates the formation of Ag 2 O or AgO layers covering metallic nanosilver.