Ferrous cysteinate nanoparticles in the form of hexagonal nanoplates up to 20 nm thick have been synthesized in aerobic conditions. Their size has been confirmed by scanning electron microscopy. Their composition, investigated using atomic emission spectroscopy with inductively coupled plasma (ICP-AES), CHNS analysis, and IR spectroscopy, has coincided with the known complex Na2Fe(cyst)2·H2O (cyst being the cysteine fragment –SCH2СН(NН2)СОО–). Using X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (XRD), the chemical transformations of the compound obtained under the action of air oxygen and moisture have been studied. Under these conditions, the Fe2+(cyst)(H2O)1.5 complex has been formed.

Having a wide range of applications, bismuth silicate-based materials (BSO) attract attention of numerous re-searchers. Typically, they are synthesized either from active chemicals or through high-energy impact on their precursors. The present work is the first report on BSO-based nanomaterials prepared via laser processing in liquid phase in which the following two-step scheme was realized: (1) Individual colloids of Bi-and Si-based nanoparticles were obtained via ablating their metallic targets in distilled water and then mixed; (2) Post-treatment of the mixed colloid was performed with the same laser beam as in stage (1). The products ob-tained after drying of non-treated and post-treated mixed colloids (denoted as samples BSO and BSO_h nu, respectively) were carefully characterized using a set of microscopic, spectroscopic and electrochemical analyses, after which their photocatalytic performance in presence of model organic dye (rhodamine B) and phenol was tested. The additional laser treatment was found to lead to active interaction between Bi-and Si-containing species and stimulated formation of phases with Bi-O-Si bonds. The post-irradiated sample BSO_h nu showed improved stability and catalytic performance, thus opening avenues for wider use of laser processing in liquids as a method allowing for preparation of nanostructures with complex chemical composition.

RF-plasma deposition of Pt on a nanosized ceria powder support has been performed directly in photoelectron spectrometer chambers to prepare model catalysts. The plasma deposition in an oxidizing environment results in the formation of highly dispersed oxide nanoparticles up to 2 nm large, which contain platinum solely as Pt4+ ions revealed by E-b(Pf4f(7/2)) = 74.6 eV. Thus prepared model catalyst samples arranged as (sub-monolayer) films of PtO2 nanoparticles on the surface of CeO2 are characterized by an increased thermal stability compared with PtO2 nanoparticles deposited on more inert supports. These PtO2/CeO2 model catalysts show a high activity in the CO oxidation even at room temperature. A detailed analysis of the Ols spectra obtained during the titration by CO of PtO2/CeO2 films strongly suggests that the reactive oxygen species are manifested with E-b(Ols) = 530.8 eV and 532.9 eV. The latter core level energies are attributed to oxygen in the platinum dioxide and to peroxide-like oxygen, presumably located at the interface between PtO2 and CeO2 particles. Results of our density-functional calculations indicate that the peroxide-like species can be energetically stabilized at the PtOx-CeO2 interfaces.

The mixed silver-copper oxide Ag2Cu2O3 with a paramelaconite crystal structure is a promising material for catalytic applications. The as-prepared sample of Ag2Cu2O3 consisted of brick-like particles extended along the [001] direction. A combination of physicochemical techniques such as TEM, XPS and XRD was applied to investigate the structural features of this mixed silver-copper oxide. The thermal stability of Ag2Cu2O3 was investigated using in situ XRD under different reaction conditions, including a catalytic CO + O-2 mixture. The first step of Ag2Cu2O3 decomposition was accompanied by the appearance of ensembles consisting of silver nanoparticles with sizes of 5-15 nm. Silver nanoparticles were strongly oriented to each other and to the surface of the initial Ag2Cu2O3 bricks. Based on the XRD data, it was shown that the release of silver occurred along the a and b axes of the paramelaconite structure. Partial decomposition of Ag2Cu2O3 accompanied by the formation of silver nanoparticles was observed during prolonged air storage under ambient conditions. The high reactivity is discussed as a reason for spontaneous decomposition during Ag2Cu2O3 storage. The full decomposition of the mixed oxide into metallic silver and copper (II) oxide took place at temperatures higher than 300 degrees C regardless of the nature of the reaction medium (helium, air, CO + O-2). Catalytic properties of partially and fully decomposed samples of mixed silver-copper oxide were measured in low-temperature CO oxidation and C2H4 epoxidation reactions. (C) 2017 Elsevier B.V. All rights reserved.

The effect of concentration of the metallic component - platinum (0.1-2 wt.%) - and its electronic state in Pt/WO3/ZrO2 catalysts on characteristics of n-heptane isomerization was studied. It was found that a rise in the platinum concentration to 1.5 wt.% increases the yield of the target products of n-heptane isomerization - high-octane di- and trimethyl-substituted isomers (DTMS). Calcination of the catalyst in flowing air was shown to facilitate the formation of charged platinum, the presence of which enhances the catalyst activity. (C) 2016 The Authors. Published by Elsevier Ltd.

Studies of highly oxidized rhodium species as potential active sites in catalytic oxidation reactions are of great interest. In this work, we investigated the properties of highly oxidized nanostructured rhodium film prepared by radio frequency discharge in an oxygen atmosphere. The charge states of Rh in RhOx particles, their thermal stability, and reactivity toward CO were analyzed in comparison with the properties of thermally prepared Rh2O3 oxide. The formation of Rh4+ species in a composition of Rh4+/Rh3+ oxyhydroxide structures was shown to take place in plasma-synthesized films. The highly oxidized rhodium species was stable up to 150 degrees C and demonstrated reactivity in a CO oxidation reaction at 100 degrees C. The reoxidation of a partially reduced Rh/RhOx film was observed at 100 degrees C under treatment with molecular O-2. However, Rh4+ species were not recovered under such conditions.

Platinum-oxide nanoparticles were prepared through the radio-frequency (RF) discharge sputtering of a Pt electrode in an oxygen atmosphere. The structure, particles size, electronic properties, and surface composition of the RF-sputtered particles were studied by using transmission electron microscopy and X-ray photoelectron spectroscopy. The application of the RF discharge method resulted in the formation of highly oxidized Pt4+ species that were stable under ultrahigh vacuum conditions up to 100 degrees C, indicating the capability of Pt4+-O species to play an important role in the oxidation catalysis under real conditions. The thermal stability and reaction probability of Pt4+ oxide species were analyzed and compared with those of Pt2+ species. The reaction probability of PtO2 nanoparticles at 90 degrees C was found to be about ten times higher than that of PtO-like structures.

Inhomogeneous surface charging could lead to a distortion of X-ray photoelectron (XP) spectra, which complicates the spectra analysis and sometimes results in an incorrect interpretation of elements chemical states of the sample. The charging effects might be especially strong in the case of XPS application for the characterization of heterogeneous catalysts, which are usually based on the dielectric or semiconductor materials with complex morphology. In this paper, we propose an algorithm to restore XP spectra when distortion is caused by inhomogeneous and/or non-constant surface charging effects. A photoelectron line of a reference element can be used to eliminate the distortions from experimental spectra of other elements by an iterative deconvolution procedure. The successful application of the algorithm for the restoration of a Pd3d line shape using a reference Sn3d(5/2) line was demonstrated for the Pd/SnO2 and Pd/CeO2-SnO2 catalysts. (C) 2015 Elsevier B.V. All rights reserved.

The paper demonstrates a new technique for preparing nanostructured films of the Pd x Ce1−x O2−x−δ solid solution. The obtained films are similar to real powder catalysts by their chemical and structural properties and are conductive, which is favorable for the XPS methoda. The effect of the CO+O2 reaction on the oxidized and reduced surfaces is studied using these model objects. The presence of the reversible “Pd x Ce1−x O2−x−δ ↔ surface palladium forms” transition occurring already at room temperatures in the CO+O2 reaction is shown. Deconvolution of the O1s spectra made it possible for the first time to separate experimentally the contributions from OH− hydroxyl and CO 3 2− carbonate surface groups.

Highly oxidized gold nanoparticles prepared by RF-discharge under an oxygen atmosphere were studied by X-ray photoelectron spectroscopy and transmission electron microscopy depending on the particle size. A surface-like gold oxide was found in the case of small nanoparticles (1–2 nm) obtained at the first steps of deposition. With an increase of the particle size up to 5 nm, a bulklike gold oxide was formed. The O 1s spectra exhibited an oxygen peak at binding energy Eb = 529.4 eV for the surface-like oxide and Eb = 530.7 eV for the bulklike gold-oxide. The reaction probability of oxidized gold nanoparticles was examined in the reaction of CO oxidation at room temperature. The surface-like gold oxide interacted with CO with a high reaction probability of approximately 0.005, while CO interaction with the bulklike oxide was characterized by an induction period with lower reaction probability (0.001). The mechanisms of the interaction of oxidized gold nanoparticles with CO depending on its size are discussed.

Mixed silver-copper oxide Ag2Cu2O3 was investigated by a combination of physicochemical techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature programmed reaction (TPR). The catalytic properties of Ag2Cu2O3 in the reaction of CO oxidation were studied by the TPR-CO + O-2 method and compared with those of CuO nanopowder characterized by a similar specific surface area. On the surface of Ag2Cu2O3, two unequivalent oxygen species (E-b(O1s)= 529.4 eV and 531 eV) with different reaction probability towards CO were observed. Previously, similar oxygen species had been found on the surface of CuO nanopowder. Mixed silver-copper oxide interacted with CO at room temperature, which resulted in the surface reduction Cu2+ -> Cu1+. Such reduction was accompanied by the removal of only oxygen with E-b(O1s) 531 eV. When the mixed oxide was heated in the reaction medium, both oxygen species were eliminated from the surface, leading to the partial decomposition of the Ag2Cu2O3 structure and the appearance of metallic silver. The TPR-CO study showed the presence of weakly bound oxygen species which can be adsorbed on oxygen vacancies in the Ag2Cu2O3 paramelaconite structure. The energy of oxygen vacancy formation on the (001) and (101) surfaces of Ag2Cu2O3 were calculated by periodic density functional theory (DFT). The role of different oxygen species in CO oxidation over the Ag2Cu2O3 surface is discussed. (C) 2015 Elsevier B.V. All rights reserved.

The low-temperature dehydrogenation of propane with O-2 and H-2 on H3PMo12O40-modified Pt catalysts has been studied and improvement of the catalyst performance achieved with the aid of promoters and operating conditions. Introduction of phosphoric acid into the catalysts results in a more uniform distribution of heteropoly acid and enables the content of Pt to be decreased to 0.05 wt.% without affecting catalyst productivity at the low temperature (200 degrees C). With Ag as the promoter, the propane combustion to CO2 can be further lowered and selectivity to propene enhanced to 94%. The best results were obtained when the consumption of H-2 and O-2 along the catalyst bed was compensated with a new portion of the reagents (two reactors in line); propene selectivity was still near 90% at overall propane conversion of 7.5% and propene space-time yield of 370 g kg(cat)(-1) h(-1). The catalysts showed little deactivation and maintained their conversion and selectivity values for the time of the measurements (5-10 h). (C) 2014 Elsevier B.V. All rights reserved.

Properties of Pt/SiO2 catalysts modified by a heteropoly acid (HPA) were studied in oxidative dehydrogenation of propane with an O-2 and H-2 mixture. The catalysts were characterized with N-2 adsorption, IRS, XPS, and HAADF-STEM coupled with EDX, and the possibility for Pt and HPA to be highly dispersed and well-mixed on the silica surface has been shown. In the presence of O-2 and H-2, propene could be obtained at temperatures as low as 150 degrees C, but heating to 200 degrees C provided much better selectivity (up to 94-96% at propane conversion of 2-4%). The process probably proceeded through oxidation of propane with peroxo species to C-3-alcohols on Pt sites, followed by dehydration of the alcohols on the acid sites of HPA. The catalytic properties were strongly dependent both on the feed composition (the C-3 H-8/H-2/O-2/N-2 ratio) and on the composition of catalysts, optimum HPA loading being 20-30 wt.% at 0.2-1 wt.% of Pt. Under optimal operating conditions, a space time yield of propene was at a level of 420 gkg(cat)(-1)h(-1) without a tendency to decline with time on stream. (C) 2014 Elsevier B.V. All rights reserved.

Copper(II) oxide nanopowders exhibit a high catalytic activity in CO oxidation at low temperatures. The combination of in situ XPS, XRD, and HRTEM methods was applied to investigate initial steps of CuO nanoparticles reduction, to identify oxygen and copper species and to revealed structural features in the dependence on reducing power of reaction medium. At the oxygen deficient surface of CuO nanopowders the metastable Cu4O3 oxide was formed under the mild reducing conditions -10(-5) mbar CO or CO + O-2 mixture with oxygen excess. Destruction of Cu4O3 structures in strong reducing medium (P(CO) >= 10(-2) mbar) or under UHV conditions resulted in the formation of Cu2O which was epitaxially bounded with initial CuO particle. The reversible bulk reduction of CuO nanopowder to Cu2O at temperatures similar to 150 degrees C can be explained by effortless propagation of Cu2O parallel to CuO epitaxial front inside the nanoparticle. The model of the surface restructuring along the {-111}CuO -> {202}Cu4O3 -> {111}Cu2O planes under the reduction of CuO nanopowders is proposed. The initial surface of CuO nanopowders is probably distorted and resembles Cu4O3-like structures that facilitates the CuOx <-> Cu4O3 transition in mild reducing conditions. Such restructuring results in a unique electronic Cu4O3 structure with high oxygen deficiency and low-valence Cu1+ sites stimulating the formation of highly reactive CO and O-2 adsorbed species. It was shown that the most active oxygen species on the surface of CuOx is stabilized as O-, which was previously reported in papers by Roberts and Madix in their study of the copper-oxygen systems.

Changes of a 65Ni25Cu10Al2O3 catalyst consisting of Ni-enriched and Cu-enriched alloys were investigated in the bulk and on the surface during the growth of nitrogen-doped carbon nanofibers （N-CNFs） by decomposition of a 50%C 2H4 /50%NH3 mixture using in situ X-ray diffraction （XRD） analysis, ex situ X-ray photoelectron spectroscopy （XPS） and transmission electron microscopy （TEM） techniques. It was shown that N-CNF growth at 450 650 C is accompanied by dissolution of carbon and nitrogen in the Ni-enriched alloy, whereas Cu-enriched alloy remains inactive. A correlation between nickel and copper surface concentrations and properties of N-CNFs in relation to the nitrogen content was found. It was demonstrated that phase composition of the catalyst during N-CNF growth determines the type of N-CNFs structure.

In production of chlorine by electrolysis of NaCl, chlorate is formed as by-product and must be removed. The back conversion of ClO3− to Cl− via catalytic reduction with H2 on Ir catalyst in NaCl brine has been studied. The catalysts contained 0.5–5wt.% of Ir and were prepared via impregnation of mesoporous carbon support (Sibunit™) with solutions of IrCl3·xHCl·yH2O or H2IrCl6 and reduction in flowing H2 at 400 or 500°C. The Ir/C samples have been characterized with CO adsorption, XPS and HRTEM. The rate of ClO3− reduction in concentrated solutions of NaCl was found dependent on pH (in the range 2–6), content of Ir in the catalyst, dispersion and distribution of Ir on the support. The best properties have been shown by 5%Ir/C catalyst which was prepared with H2IrCl6 as the metal precursor and contained small Ir particles (∼1.5nm in diameter) located inside the cavities of carbon globules. Stable catalytic performance in multiple successive runs has been achieved.

The deposition of Pt oxide from aqueous chloroplatinate solutions onto carbon supports (activated carbons, carbon blacks, carbon nanofibers) with the aid of Na2CO3 and without adding the reductants or wetting agents was studied. It has been revealed that carbons accelerate greatly the hydrolysis of chloroplatinate, and the hydrolytic deposition can therefore interfere with the other preparation methods. Neutral pH was found optimum for heterogeneous nucleation and formation of smaller PtOx particles. High temperature (80°C) allowed depositions of 5–30wt.% of Pt for a short time (1–3h) but did not affect Pt dispersions (15–90% at surface concentration of Pt 0.5–30μmol/m2). The supported particles could be further reduced in the liquid phase with minimal losses of the dispersion (Na-formate as reductant). The heterogeneous nucleation ensured a uniform distribution of Pt particles but provoked particle confinement in narrow pores. The possibility of influencing catalytic properties with the aid of the support, Pt loading and deposition conditions was demonstrated (hydrogenation of cycloalkenes as a model structure-insensitive reaction and oxidation of isopropyl alcohol as structure-sensitive one).

The formation of Pd0.05Ce0.95O2 catalysts for the low-temperature oxidation of CO by the thermal decomposition of Ce(NO3)3 and Pd(NO3)2 with oxygen was studied by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) directly in the preparation chamber of a spectrometer. Palladium is represented by two species on the surface of the catalysts: solid solutions of PdxCe1−xO2−δ and palladium clusters. Pd clusters can be formed in an oxidized or reduced state depending on the reaction conditions. Treatment of the catalysts with hydrogen leads to a sharp increase in CO conversion because of the reduction of parts of the palladium accompanying the formation of the metallic clusters. The testing of “real” and model catalysts was conducted in a light-off mode. The correlation between the activity of the Pd/CeO2 catalysts and the states of the palladium was proposed.

CuO nanopowders were prepared by precipitation from alkaline solutions and were studied by TPR-CO+O2, 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 T50 values of 110°C. In contrast, bulk CuO oxides with sizes greater than 450nm 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 CuO1−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 Eb(O1s)=531.3eV 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.

Oxidized palladium nanoparticles, PdOx (x approximate to 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 similar to 336.5 and 338.6 eV, which were assigned to Pd2+ and Pd4+ species, respectively. Attempts to synthesize pure Pd4+ nanoparticles by plasma treatment without the presence of Pd2+ 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 similar to 425-450 K. The oxidized palladium species (Pd4+) 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.