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1.
In the case of a hypothetical severe accident in a nuclear power plant, interactions of gaseous RuO4 with reactor containment building surfaces (stainless steel and epoxy paint) could possibly lead to a black Ru-containing deposit on these surfaces. Some scenarios include the possibility of formation of highly radiotoxic RuO4(g) by the interactions of these deposits with the oxidizing medium induced by air radiolysis, in the reactor containment building, and consequently dispersion of this species. Therefore, the accurate determination of the chemical nature of ruthenium in the deposits is of the high importance for safety studies. An experiment was designed to model the interactions of RuO4(g) with samples of stainless steel and of steel covered with epoxy paint. Then, these deposits have been carefully characterised by scanning electron microscopy (SEM/EDS), electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). The analysis by XPS of Ru deposits formed by interaction of RuO4(g), revealed that the ruthenium is likely to be in the IV oxidation state, as the shapes of the Ru 3d core levels are very similar with those observed on the RuO2·xH2O reference powder sample. The analysis of O 1s peaks indicates a large component attributed to the hydroxyl functional groups. From these results, it was concluded that Ru was present on the surface of the deposits as an oxyhydroxide of Ru(IV). It has also to be pointed out that the presence of “pure” RuO2, or of a thin layer of RuO3 or Ru2O5, coming from the decomposition of RuO4 on the surface of samples of stainless steel and epoxy paint, could be ruled out. These findings will be used for further investigations of the possible revolatilisation phenomena induced by ozone. 相似文献
2.
K.S. Kim W.E. Baitinger J.W. Amy N. Winograd 《Journal of Electron Spectroscopy and Related Phenomena》1974,5(1):351-367
ESCA has been used to monitor alterations of catalytically and electrochemically important metal-oxygen surfaces following exposure to Ar+ and O2+ ion bombardment. This treatment resulted not only in sputtering, but also, in many cases, in reduction to the corresponding metal or lower oxide. A model based on bulk thermodynamic free energy considerations Is proposed to explain this phenomenon. We have also exploited this approach to obtain an in-depth concentration profile of various oxidation states of an element, to selectively prepare desired surface oxide compositio and to aid in interpreting complex O ls spectra. Results obtained from metal-oxygen surfaces for Ni, Ru and Mo are presented. Ni2O3 and RuO3, which are gross defect structures of the bulk species, are present on NiO and RuO2 respectively, with the former being confined to the surface layers. The MoO2, on the other hand, is covered with a surface layer of MoO3 present as a regular crystal structure. 相似文献
3.
Hydrous ruthenium dioxide, RuO2·xH2O, is a material of active investigation as an electrode material for supercapacitors. A combination of elastic and inelastic neutron scattering together with thermal gravimetric studies and DFT calculations have provided new insight into the nature of the surface species present on RuO2·xH2O. Our results confirm that hydrous ruthenium oxide is a nanocrystalline material consisting of a core of RuO2. We show that the surface consists largely of Ru–OH with small amounts of water hydrogen-bonded to the surface. The hydroxyls are stable up to ~200°C, i.e. over the composition range x?=?0.2–2. The optimal supercapacitor material has x?=?0.5–0.7, and in this range, the surface is fully hydroxylated. This provides a route for the proton transport: a proton can attach to a surface hydroxyl to generate coordinated water, proton transport then occurs along the hydrogen-bonded chain by a Grotthuss mechanism. 相似文献
4.
X-ray K-absorption studies of ruthenium in ruthenium metal,RuO2, K2(RuCl6) and K4[Ru(CN)6]: 3H2O have been carried out using 400 mm bent crystal (mica) spectrograph. K-absorption edge of ruthenium in these compounds lies on the higher energy side with respect to that in the ruthenium metal; the divalent K4[Ru(CN)6]·3H2O gives the shift in the range of tetravalent compounds RuO2 and K2[RuCl6]. This discrepancy has been explained on the basis of molecular orbital picture. 相似文献
5.
《Current Applied Physics》2018,18(10):1143-1148
With developments in energy storage devices, supercapacitors are gaining more attraction because of their potential to excel batteries shortly. In this work, ruthenium oxide (RuO2) has been deposited on stainless steel and studied the influence of surface modification of solid electrodes on capacitance properties. Hydrous ruthenium oxide was plated by different modes such as potential sweep method (cyclic voltammetric), constant potential method (chronoamperometry) and optimised potential pulse method using a recently reported precursor material namely ruthenium nitrosylsulfate (RuNS). The structural information and morphology of electrodeposits were characterised by X-ray diffractometer and scanning electron microscope respectively. The XRD studies indicate a poor crystalline state for RuO2 in all the modes of deposition but can contribute to a higher surface area when compared to a highly crystalline form. The SEM analysis revealed the formation of surface modification concerning the change of potential mode. Mud-cracked morphology, spherical particles and dendrimeric morphology observed on chronoamperometry, potential pulse and cyclic voltammetry respectively. Electrochemical studies were also conducted on the samples to assess their performance for supercapacitor applications. The spherical particles of hydrous RuO2 show high performance of capacitance behaviour 1180 F/g in 0.5 M H2SO4 at the scan rate of 5 mV/s. Dendrimeric morphology and mud-cracked morphology shows 573 F/g and 546 F/g respectively in same 0.5 M H2SO4 at the scan rate of 5 mV/s. The studies reveal that RuO2 electrodes can be exploited for their outstanding capacitive behaviour by properly controlling the morphology of the deposits. 相似文献
6.
X-ray photoelectron spectroscopy was used to study the effect of atomic oxygen on Ru(0 0 0 1), and the effect of dissociated ammonia on RuO2/Ru(0 0 0 1), in UHV conditions at ambient temperature. The Ru(0 0 0 1) surface was exposed, at ambient temperature, to a mixed flux of atomic and molecular oxygen generated by dissociation of O2 in a thermal catalytic cracker, with 45% dissociation efficiency. The detailed study of the XPS spectra shows the formation of a disordered multilayer oxide (RuO2). No formation of higher oxides of Ru was observed. The formation of RuO2 proceeded without saturation for total oxygen exposures of up to 105 Langmuir, at which point an average oxide thickness of 68 Å was observed. RuO2 formed by the reaction with atomic oxygen was exposed to a flux of NHx (x = 1, 2) + H generated by the cracker. The reduction of RuO2 to Ru metal was observed by XPS. An exposure of 3.6 × 102 L of NHx + H, resulted in the observation of adsorbed H2O and OH, but no evidence of lattice oxide. The chemisorbed species were removed by additional NHx + H exposure. No nitrogen adsorption was observed. 相似文献
7.
H. Over 《Applied Physics A: Materials Science & Processing》2002,75(1):37-44
Over the past few years, RuO2 has developed into one of the best-characterized late transition metal oxides in surface science, revealing unique and promising
redox properties. The CO oxidation reaction over RuO2 (110) was intensively studied by low-energy electron diffraction, scanning tunneling microscopy, high resolution core level
spectroscopy, and density functional theory calculations, connecting structural and electronic properties with chemical properties.
On the atomic scale the presence of one-fold coordinatively unsaturated Ru sites (1f-cus Ru) is the primary reason for the
high activity of stoichiometric RuO2 (110) towards the oxidation of CO and other small alcohols. On the stoichiometric RuO2 (110) surface, CO molecules adsorb strongly (adsorption energy exceeding 1.2 eV) on top of the 1f-cus Ru atoms, from where
the actual oxidation reaction step takes place via recombination with under-coordinated lattice oxygen to form CO2 (the so-called Mars–van Krevelen mechanism); the conversion probability of this process is as high as 80%. This mechanism
leads to a (partial) reduction of the RuO2 (110) surface, producing two-fold coordinatively unsaturated Ru sites (2f-cus Ru) via the removal of bridging O atoms. Therefore,
equally important for being a good catalyst is the facile re-oxidation of the mildly reduced RuO2 (110) surface by oxygen supply from the gas phase. A weakly held oxygen species was found to adsorb on top of the 1f-cus
Ru atoms and to actuate the restoration of the reduced RuO2 (110) surface. On the reduced RuO2 (110) surface, CO molecules adsorb in bridge sites above the 2f-cus Ru atoms by 1.85 eV, while the CO bond strength over
1f-cus Ru atoms is 1.61 eV.
Received: 27 March 2001 / Accepted: 23 July 2001 / Published online: 3 April 2002 相似文献
8.
To study the fate of a molecular di‐μ‐oxo‐bridged trinuclear ruthenium complex, [(NH3)5Ru–O–Ru(NH3)4–O–Ru(NH3)5]6+, also known as Ru‐red, during the electro‐driven water oxidation reaction, electrochemical in situ surface enhanced Raman spectroscopy (SERS) investigations have been conducted on an electrochemically roughened gold surface in acidic condition. It was previously described that on a basal plane pyrolitic graphite electrode in 0.1 M H2SO4 aqueous solution, Ru‐red undergoes one electron oxidative conversion into a stable higher oxidation state ruthenium complex, Ru‐brown, at <1.0 V (vs normal hydrogen electrode (NHE)), and this leads to water oxidation and dioxygen release, but the fate of Ru‐red during electrochemistry was not studied in much detail. In this investigation, Ru‐red dispersed in acid electrolyte and immobilized on a roughened gold electrode without Ru‐red in solution has been subjected to anodic controlled potential experiments, and in situ SERS was carried out at various potentials in succession. The electrochemical SERS data obtained for Ru‐red are also compared with in situ SERS results of an electrodeposited ruthenium oxide thin film on the Au disk. Our study suggests that on a gold electrode in sulfuric acid solution containing Ru‐red, one electron oxidative conversion of Ru‐red to a higher oxidation state ruthenium compound, Ru‐brown, occurs at ca. 0.74 V (vs NHE), as supported by the electrochemical in situ SERS experiments. Moreover, at higher potentials and on Au disk, the Ru‐red / Ru‐brown are not stable and slowly decompose or electro‐oxidize leading to deactivation of the tri‐ruthenium catalytic system in acidic medium. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
9.
The oxidation and reduction of Ru thin films grown on a Si(1 0 0) surface were studied by X-ray photoemission spectroscopy (XPS). Ru thin films were oxidized with O2 plasma generated by an rf discharge, and their XPS spectra were measured. The spectra were decomposed into several components for Ru suboxides attributable to different stages of oxidation. After sufficient exposure to oxygen, a stoichiometric rutile RuO2 layer was found to have formed near the surface. Thermal annealing at 500 K resulted in a thicker RuO2 layer. Experiments demonstrated that the Ru oxide layer can be removed by H(D) atoms via the desorption of water molecules. 相似文献
10.
A.J. Hartmann M. Neilson R.N. Lamb K. Watanabe J.F. Scott 《Applied Physics A: Materials Science & Processing》2000,70(2):239-242
Metallic ruthenium and ruthenium oxides, such as SrRuO3 and RuO2, are potential electrode materials for ferroelectric capacitors. The electrical properties (e.g. leakage currents) of such thin film devices are dependent on the electronic properties of the electrode/ferroelectric junctions and therefore also on the electrode work functions. During growth and processing of film-electrode layer structures the formation of sub-oxides within the electrode is possible, with their work functions being unknown. In order to obtain information for predicting device properties, we have systematically analysed the valence bands and work functions of RuOx and SrRuOy thin films with different oxidation states by using photoelectron spectroscopy techniques. The results suggest that Ru0 and Ru4+ ions are present in co-existence at the surfaces of oxygen-deficient polycrystalline films (inhomogeneous oxidation). For both oxygen-deficient materials the work function coincides with that of metallic ruthenium (4.6ǂ.1 eV). Only for fully oxidised ruthenium oxide and strontium ruthenate films (no Ru0 present at the surface) is the work function increased to 5.0 or 4.9 eV, respectively. As an example of importance for new dynamic random access memory applications, the junctions of Ba1-xSrxTiO3 with SrRuOy and RuOx are discussed. 相似文献
11.
Yurii V. Larichev Boris L. Moroz Valerii I. Bukhtiyarov 《Applied Surface Science》2011,258(4):1541-1550
The electronic state of ruthenium in the supported Ru/EOx (EOx = MgO, Al2O3 or SiO2) catalysts prepared by with the use of Ru(OH)Cl3 or Ru(acac)3 (acac = acetylacetonate) and reduced with H2 at 723 K is characterized by X-ray photoelectron spectroscopy (XPS) in the Ru 3d, Cl 2p and O 1s regions. The influence of the final state effects (the differential charging and variation of the relaxation energy) on the binding energy (BE) of Ru 3d5/2 core level measured for supported Ru nanoparticles is estimated by comparison of the Fermi levels and the modified Auger parameters determined for the Ru/EOx samples with the corresponding characteristics of the bulk Ru metal. It is found that the negative shift of the Ru 3d5/2 peak which is observed in the spectrum of ruthenium deposited onto MgO (BE = 279.5-279.7 eV) with respect to that of Ru black (BE = 280.2 eV) or ruthenium supported on γ-Al2O3 and SiO2 (BE = 280.4 eV) is caused not by the transfer of electron density from basic sites of MgO, as considered earlier, but by the differential charging of the supported Ru particles compared with the support surface. Correction for the differential charging value reveals that the initial state energies of ruthenium in the Ru/EOx systems are almost identical (BE = 280.5 ± 0.1 eV) irrespectively of acid-base properties of the support, the mean size of supported Ru crystallites (within the range of 2-10 nm) and the surface Cl content. The results obtained suggest that the difference in ammonia synthesis activity between the Ru catalysts supported on MgO and on the acidic supports is accounted for by not different electronic state of ruthenium on the surface of these oxides but by some other reasons. 相似文献
12.
Amorphous and porous ruthenium oxide thin films have been deposited from aqueous Ru(III)Cl3 solution on stainless steel substrates using electrodeposition method. Cyclic voltammetry study of a film showed a maximum specific capacitance of 650 F g−1 in 0.5 M H2SO4 electrolyte. The surface treatments such as air annealing, anodization and ultrasonic weltering affected surface morphology. The supercapacitance of ruthenium oxide electrode is found to be dependent on the surface morphology. 相似文献
13.
M. Khachane P. Nowakowski J.R. Gavarri Ch. Muller A. Outzourhite A. Zegzouti 《Applied Surface Science》2007,254(5):1399-1404
Catalytic ruthenium dioxide films were deposited by spin-coating process on ferroelectric films mainly constituted of SrBi2Ta2O9 (SBT) and Ba2NaNb5O15 (BNN) phases. After thermal treatment under air, these ferroelectric-catalytic systems were characterized by X-ray diffraction and scanning electron microscopy (SEM). SEM images showed that RuO2 film morphology depended on substrate nature. A study of CH4 conversion into CO2 and H2O was carried out using these catalytic-ferroelectric multilayers: the conversion was analyzed from Fourier transform infrared (FTIR) spectroscopy, at various temperatures. Improved catalytic properties were observed for RuO2 films deposited on BNN oxide layer. 相似文献
14.
The charging processes and methanol oxidation that occur during the oxidation-reduction cycles in a ruthenium oxide thin film electrode (deposited by the sol-gel method on Pt covered quartz crystals) were investigated by using cyclic voltammetry, chronoamperometry and electrochemical quartz crystal nanobalance techniques. The ruthenium oxide rutile phase structure was determined by X-ray diffraction analysis. The results obtained during the charging of rutile ruthenium oxide films indicate that in the anodic sweep the transition from Ru(II) to Ru(VI) occurs followed by proton de-intercalation. In the cathodic sweep, electron injection occurs followed by proton intercalation, leading to Ru(II). The proton intercalation/de-intercalation processes can be inferred from the mass/charge relationship which gives a slope close to 1 g mol−1 (multiplied by the Faraday constant) corresponding to the molar mass of hydrogen. From the chronoamperometric measurements, charge and mass saturation of the RuO2 thin films was observed (440 ng cm−2) during the charging processes, which is related to the total number of active sites in these films. Using the electrochemical quartz crystal nanobalance technique to study the methanol oxidation reaction at these films was possible to demonstrate that bulk oxidation occurs without the formation of strongly adsorbed intermediates such as COads, demonstrating that Pt electrodes modified by ruthenium oxide particles can be promising catalysts for the methanol oxidation as already shown in the literature. 相似文献
15.
为了说明钡助剂的存在形式, 本文采用第一性原理方法研究了BaxOy小团簇修饰Ru(0001)表面的结构稳定性和氮分子吸附性质. 基于总能的热力学分析发现, 在实验条件下(500 K, PH2O/PH2<10-3), Ba2O团簇比BaO2, BaO, Ba和O等团簇(原子)更加稳定. 这证实含有金属性钡原子的团簇也是氧化钡助剂可能的工作状态. 表面电荷差分密度说明Ba2O团簇的氧和钡原子与衬底的作用不同. 不过Ba2O团簇氧和钡原子附近的氮分子吸附行为相似, Ba2O团簇增强了氮分子和衬底的相互作用. Ba2O团簇氧和钡原子附近的氮分子吸附能分别为0.78 和0.88 eV, 均大于清洁表面的0.67 eV. 氮分子间距和氮分子的拉伸振动频率都表明Ba2O团簇在一定程度上活化了吸附氮分子. Ba2O团簇氧和钡原子附近的N–N键长分别为0.117和0.116 nm, 大于清洁表面的0.114 nm. 氧和钡原子附近氮分子的拉伸振动频率分别为 1888 和1985 cm-1, 小于清洁表面的2193 cm-1. 电荷差分密度的计算结果说明, 削弱作用主要来自于Ba2O团簇中钡离子和氮分子间的静电作用. 两者间的静电作用增加了氮分子π 反键轨道的占据数, 促进了氮分子极化, 从而削弱氮分子键. 相似文献
16.
X-Ray Photoelectron Spectroscopy (XPS), Metastable Induced Electron Spectroscopy (MIES) and Ultraviolet Photoelectron Spectroscopy (UPS) were applied to study the interaction of H2O molecules with iron films.During the interaction with H2O molecules under ultrahigh vacuum conditions, an oxide film is formed on the iron surface. UPS and XPS still show metallic contributions, even for a surface which is exposed to about 103 L. The oxide film thickness amounts to about 1.8 nm. No hydroxide formation is observed at all, neither in UPS nor in MIES. Further impinging H2O molecules do not interact with the surface, because the oxide film inhibits the dissociation of impinging molecules.H2O exposure beyond 109 L does not lead to a significant increase of the oxide layer, which saturates at a thickness of 1.8 nm. In particular, no surface hydroxide is observed at this exposure. Neither XPS UPS nor MIES reveal any indication for this. 相似文献
17.
18.
Atomistic static computer simulation techniques have been applied to investigate the energetics of defects and dopants in Sr2RuO4 (SRO) and Ca2RuO4 (CRO). Interatomic potentials have been derived which reproduced the crystal structures of these systems. Solution energies are calculated for different dopant ions to ascertain the site occupied by the dopant ion in the host lattice. Monovalent and divalent ions are predicted to substitute preferentially at the alkaline-earth site in both the systems. Trivalent cations of smaller ionic radii substitute at the Ru sites while those having larger ionic radii prefer to substitute at the Sr or Ca sites in SRO or CRO systems, respectively. In addition, there is a possibility of self-compensation, where a trivalent cation can substitute at both Sr(Ca) and Ru sites. Tetravalent dopants are found to substitute at the ruthenium sites in both systems. 相似文献
19.
V.D. Patake 《Applied Surface Science》2008,254(9):2820-2824
Ruthenium oxide (RuO2) thin films have been prepared using single step chemical method containing Ru(III) Cl3 solution in an aqueous medium at low temperature. The structural, morphological and optical properties have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and optical absorption technique. The XRD study revealed the formation of amorphous RuO2 thin film. The surface examination by SEM showed formation of nano-porous material on the substrate. The TEM study revealed the formation of nanostructured material. The optical absorption studies showed the presence of direct band transition with band gap equal to 2.2 eV. The RuO2 has proved its applicability in supercapacitor showing 50 F/g specific capacitance in 0.5 M H2SO4 at 20 mV/s scan rate. 相似文献
20.
W. Potzel F. E. Wagner R. L. Mössbauer G. Kaindl H. E. Seltzer 《Zeitschrift für Physik A Hadrons and Nuclei》1971,241(2):179-187
The recoilless nuclear gamma resonance of the 127 keV γ-rays of101Ru was observed in ruthenium metal, RuO2 and [Ru(NH3)4(HSO3)2]. By comparison of the isomer shifts observed in these materials for the 127 keV absorption line with the corresponding shifts of the 90keV γ-rays of99Ru one obtains δ〈r 2〉 [127 keV]/ δ〈r 2〉 [90 keV]=1.78±0.26 for the ratio of the changes of the mean square nuclear charge radii between the first excited and the ground states in these nuclei. An estimate of electron density differences based on free-ion relativistic self-consistent field calculations yields δ〈r 2〉[90keV]≈+1.4·10?3 for99Ru and δ〈r 2〉/〈r 2〉 [127 keV]≈+2.4·10?3 for the101Ru case. These results are discussed in terms of the core excitation model. 相似文献