Pt/RuO2/CNTs纳米催化剂中RuO2含量对甲醇电催化氧化性能的影响

制备了一种新的甲醇直接燃料电池Pt/RuO2/CNTs阳极催化剂,在相同Pt负载量下,其甲醇电催化氧化活性是Pt/CNTs的3倍.采用循环伏安法研究发现Pt/RuO2/CNTs纳米催化剂中RuO2含量对甲醇电催化氧化活性有明显影响,当Pt和RuO2在碳纳米管上含量分别为15%和9.5%时,Pt/RuO2/CNTs催化剂具有最佳的甲醇电催化氧化活性.RuO2负载在碳纳米管上比电容的变化,反映了水合RuO2结构中质子与电子传输平衡的能力,分析表明,催化剂中RuO2含量不同导致电容的变化是影响甲醇电催化氧化活性的主要原因.当催化剂结构中质子与电子传输达到平衡时,催化剂比电容最大,电催化氧化活性最高.这种基于电容关联电催化剂的观点对甲醇直接燃料电池阳极催化剂的设计非常有意义.     

Adsorption of platinum on the stoichiometric RuO2(110) surface

Density functional theory was used to calculate the geometries and electronic structures of Pt adsorption on the stoichiometric RuO(2)(110) surface at different coverages. The calculated results revealed that the Pt atoms strongly adsorb on RuO(2), and two-dimensional growth up to 1.25 ML deposition is energetically favorable. At low coverage, the binding between Pt and RuO(2) is very strong, accompanied by a significant transfer of electron density from Pt to the support and a large downshift of the d-band compared to that of the unsupported Pt. At high coverage, a weak interaction of RuO(2) with the Pt cluster is observed, and the electronic structure of Pt is only slightly modified with respect to that of the unsupported material. Our results suggest that among the systems investigated, the RuO(2)-supported Pt at a coverage of 1 ML may become one of the best alternatives to pure Pt as a catalyst because it combines a high stability and a moderate activity similar to Pt.     

Surface chemistry study of RuO2/IrO2/TiO2 mixed-oxide electrodes

DSA metal oxide electrodes such as the RuO(2)/IrO(2)/TiO(2) mixed system are widely studied for their excellent electrocatalytic activity. In order to understand their catalytic properties, the comprehension of the surface chemistry involved during electrochemical treatments is crucial. With this aim, RuO(2)/IrO(2)/TiO(2) mixed-oxide electrodes having various noble metal contents were studied by means of secondary ion mass spectrometry (SIMS). In particular, cathodic and anodic polarization and O(2) evolution reactions were carried out to test the electrode behaviour and SIMS analyses were performed after all these treatments. In this way, surface changes induced by electrochemical treatments and depending on electrode composition were widely investigated by SIMS, revealing, for example, the presence of hydration or preferential dissolution phenomena induced by electrochemical processing.     

Structures and catalytic properties of PtRu electrocatalysts prepared via the reduced RuO2 nanorods array

Structures and properties of PtRu electrocatalyts, derived from the aligned RuO2 nanorods (RuO2NR), are investigated using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and cyclic voltammetry toward COads and methanol oxidation. The catalytic activity of methanol oxidation and the CO tolerance are promoted significantly by reducing RuO2 into Ru metal before decorating with Pt. Reduction of RuO2NR was carried out by either thermal decomposition at 650 degrees C in vacuum or H2-reduction at 130 degrees C in low-pressure hydrogen. Reduction assisted by hydrogen allows infiltrating decomposition at low temperature and produces an array of nanorods with rugged walls featuring small Ru nuclei and larger surface area. Pt-RuNR, whose surface Pt:Ru ratio=0.58:0.42 was prepared by decorating with 0.1 mg cm(-2) Pt on the H2-reduced array containing 0.39 mg cm(-2) Ru, demonstrates a favorable combination of CO tolerance and high methanol oxidation activity superior to other RuO2NR-derived catalysts. When compared with a commercial electrocatalyst of PtRu (1:1) alloy (<4 nm), the activity of Pt-RuNR in methanol oxidation is shown to be somewhat lower at potential<0.48 V and higher at potential>or=0.48 V.     

The oxidation of water by cerium(IV) catalysed by nanoparticulate RuO2 on mesoporous silica

Mesoporous silicates are prepared by templating on the hexagonal (H1) mesophase of surfactant bipyridine complexes of ruthenium(II) using a true liquid-crystal templating approach. On calcination, the surfactant template is removed except for the central metal ion that is oxidised, forming nanoparticles of RuO2 that deposit within the pores. RuO2 is a known oxidation catalyst and, despite its anhydrous nature in these silicates, is found to be very active in catalyzing the oxidation of water by acidic CeIV.     

Preparation and Performances of RuO2/TiO2 Films Photocatalyst Supported on Float Pearls

"RuO2/TiO2 films were deposited on float pearls (FP) by the sol-gel-dipping method. The substrates were coated with RuO2/TiO2 precursor sol, air-dried at 120 oC and further heated at 500 oC to obtain the coupled photocatalyst of RuO2/TiO2 films supported on FP (RuO2/TiO2/FP). The structure of coupled photocatalyst was characterized by SEM, XRD, and FT-IR technique, respectively. The results showed TiO2 has anatase structure and doped RuO2 was highly dispersed on the surface of TiO2 particles as amorphous. The average thickness of RuO2/TiO2 films (3 layers) on FP was determined to be about 1 1m. This study was carried out under the following conditions: volume 60 mL, initial concentration of beta-cypermethrin (BEC) 45 mg/L, pH 6.5, amount of RuO2/TiO2/PF 5 g/L, air flow rate 200 mL/min, reaction time 60 min. The degradation rates of BEC are 88.1% (125 W Hg lamp), 82.8% (8 W UV lamp), and 75.1% (8 W solar lamp), respectively. The photocatalytic degradation of BEC was experimentally demonstrated to follow the Langmuir-Hinshelwood kinetic model, and the reaction rate constant (17.5 mg/(L min)) and the adsorption constant (3.486 L/g) were determined, respectively. It was also found that the RuO2/TiO2 /FP photocatalyst has significantly the visible light photoactivity for degradation of BEC."     

Core level X-ray photoelectron emission spectra and structure-surface related multi-excitonic photoluminescence with reduced recombination rate in mesoporous TiO2/RuO2/CuO nanomaterials

Journal of Sol-Gel Science and Technology - Highly textured mixed metal oxide nano systems consisting of TiO2, RuO2, and CuO (TiO2/RuO2/CuO) were developed through triblock copolymer and Pluronic...     

RuO2电极的析氧活性研究

本文用XPS, UPS和电化学方法研究了RuO2电极的活怀中心组成及其在电解过程中的变化。结果表明, RuO2电极的活性中心为氧结构空位。在电解过程中,表层的氧结构空位不断减少, 由于RuO2电极析氧反应区域不断扩展和深入, 又暴露出新的氧结构空位, 但电极外表面的氧结构空位对电极析氧活性影响较大, 外表面氧结构空位为RuO2电极有效的活性中心。此外, 电极的腐蚀和剥落也是导致活性降低的原因之一。     

热分解制备的RuO2-IrO2电极研究

本文应用XPS和电化学技术研究热分解制备RuO2-IrO2电极的电化学性能和表面性质的关系, 以探讨制备寿命长, 价格低的阳极的可能途径。     

CeO2掺杂RuO2/γ-Al2O3催化剂结构与湿式氧化降解苯酚的活性研究

采用浸渍法制备了RuO2/γ-Al2O3和RuO2-CeO2/γ-Al2O3催化剂,利用XRD,XPS和ESR分析了催化剂的结构,并研究了湿式氧化降解苯酚的活性.结果表明,两种催化剂表面RuO2均有良好的分散性,并且催化剂表面存在氧空位和化学吸附氧,CeO2的掺杂使催化剂表面氧空位和化学吸附氧数量增加.两种催化剂对湿式氧化降解苯酚具有良好的催化活性,当苯酚质量浓度为4200mg/L,在150℃和3MPa下,RuO2/γ-Al2O3催化剂湿式氧化降解苯酚反应150min后,苯酚全部被去除,RuO2-CeO2/γ-Al2O3催化剂反应60min后,苯酚的去除率为96%.     

Photocatalytic activity of the RuO2-dispersed composite p-block metal oxide LiInGeO4 with d10-d10 configuration for water decomposition

The ruthenium oxide-loaded composite p-block metal oxide LiInGeO4 with d10-d10 configuration exhibited high photocatalytic activity for the overall splitting of water to produce H2 and O2 under UV irradiation. Changes in the photocatalytic activity with the calcination temperature of LiInGeO4, the amount of RuO2 loaded, and the states of RuO2 indicated that the combination of highly crystallized LiInGeO4 and a high dispersion of RuO2 particles resulted in high photocatalytic activity. Structurally, LiInGeO4 contained heavily distorted InO6 octahedra and GeO4 tetrahedra, generating a dipole moment inside. The high photocatalytic performance of RuO2-loaded LiInGeO4 supports the existing view that the photocatalytic activity correlates with the dipole moment. The DFT calculation showed that the top of the valence band (HOMO) was composed of the O 2p orbital while the bottom of the conduction band (LUMO) was formed by the hybridized In 5s5p + Ge 4s4p + O 2p orbitals. The highly dispersed conduction band, indicative of a high mobility of photoexcited electrons, was responsible for the high photocatalytic performance.     

Gasification reaction of organic compounds catalyzed by RuO2 in supercritical water

Nearly complete gasification of organic compounds has been achieved by stoichiometrically insufficient amounts of RuO2 in supercritical water (SCW) to provide CH4, CO2 and H2, all the hydrogen atoms of which originate from water, and the catalytic effect of RuO2 results from a redox couple of Ru(IV)/Ru(II) induced by SCW.     

Mechanism of RuO2 crystallization in borosilicate glass: an original in situ ESEM approach

Ruthenium, a fission product arising from the reprocessing of spent uranium oxide (UOX) fuel, crystallizes in the form of acicular RuO(2) particles in high-level waste containment glass matrices. These particles are responsible for significant modifications in the physicochemical behavior of the glass in the liquid state, and their formation mechanisms are a subject of investigation. The chemical reactions responsible for the crystallization of RuO(2) particles with acicular or polyhedral shape in simplified radioactive waste containment glass are described. In situ high-temperature environmental scanning electron microscopy (ESEM) is used to follow changes in morphology and composition of the ruthenium compounds formed by reactions at high temperature between a simplified RuO(2)-NaNO(3) precursor and a sodium borosilicate glass (SiO(2)-B(2)O(3)-Na(2)O). The key parameter in the formation of acicular or polyhedral RuO(2) crystals is the chemistry of the ruthenium compound under oxidized conditions (Ru(IV), Ru(V)). The precipitation of needle-shaped RuO(2) crystals in the melt might be associated with the formation of an intermediate Ru compound (Na(3)Ru(V)O(4)) before dissolution in the melt, allowing Ru concentration gradients. The formation of polyhedral crystals is the result of the direct incorporation of RuO(2) crystals in the melt followed by an Ostwald ripening mechanism.     

Structural phase transition of Gd3RuO7

Structural phase transition of trigadorinium ruthenium heptaoxide, Gd(3)RuO(7), has been investigated by in situ high-temperature single-crystal X-ray diffraction. A small shrinkage in b-length and an expansion in c-length were observed between 363 and 383 K with increasing temperature. No significant change occurred in a-length within experimental errors. The changes were essentially reversible against temperature. Structures of the high-temperature modification have been determined at 423, 773, and 1223 K assuming the orthorhombic Cmcm symmetry. The structure of the low-temperature modification has been determined at 293 K, assuming the orthorhombic P2(1)nb symmetry with doubled unit cell along the b-axis of the high-temperature modification. The transition from high- to low-temperature modification can be structurally characterized by tilts about axes close to the c-axis of the unit cell occurring on half of the RuO(6) octahedra. These octahedral tilts couple with a reduction in coordination number of the Gd atom bridging the adjacent RuO(6) single chains along the b-axis. The present study also revealed the presence of structural disorder in the high-temperature Cmcm modification that had not been reported for the archetypal Cmcm structures of lanthanide ruthenates (Ln(3)RuO(7)) and osmates (Ln(3)OsO(7)) in the literature. The disorder includes a dynamical or static distribution of one-third of Gd atoms in the unit cell, which is presumably linked to the libration of the octahedral tilts about the axes close to c.     

The role of weakly bound on-top oxygen in the catalytic CO oxidation reaction over RuO2(110)

RuO(2)-based catalysts are much more active in the oxidation of CO than related metallic Ru catalysts. This high catalytic activity (or low activation barrier) is attributed to the weak oxygen surface bonding of bridging O atoms on RuO(2)(110) in comparison with the strongly chemisorbed oxygen on Ru(0001). Since the RuO(2)(110) surface is able to stabilize an even more weakly bound on-top oxygen species, one would anticipate that the catalytic activity will increase further under oxidizing conditions. We will show that this view is far too simple to explain our temperature-programmed reaction experiments, employing isotope labeling of the potentially active surface oxygen species on RuO(2)(110). Rather, both surface O species on RuO(2)(110) reveal similar activities in oxidizing CO.     

Adsorption and interaction of ethylene on RuO2(110) surfaces

Ethylene (C2H4) adsorbed on the stoichiometric and oxygen-rich RuO2(110) surfaces, exposing coordinatively unsaturated Ru-cus and O-cus atoms, is investigated by applying high-resolution electron energy-loss spectroscopy and thermal desorption spectroscopy in combination with isotope labeling experiments. On the stoichiometric RuO2(110) surface C2H4 adsorbs and desorbs molecularly. In contrast, on the oxygen-rich RuO2(110) surface ethylene adsorbs molecularly at 85 K and is completely oxidized through interaction with O-cus and O-bridge upon annealing to 500 K. The first couple of reactions are observed at 200 K taking place on Ru-cus: A change from pi- to sigma-bonding, formation of -C=O and -C-O groups, and dehydrogenation giving rise to H2O adsorbed at Ru-cus. Maximum reaction rate is reached for C2H4 chemisorbed at Ru-cus with O-cus neighbors on each side. A model for the first couple of reactions is sketched. For the final combustion, C2H4 reacts both with O-cus and O-bridge. Ethylene oxide is not detected under any circumstance.     

Crystal growth, observation, and characterization of the low-temperature structure of the fluorite-related ruthenates: Sm(3)RuO(7) and Eu(3)RuO(7)

The compounds Sm(3)RuO(7) and Eu(3)RuO(7) were grown as single crystals from molten hydroxide fluxes. They crystallize in the orthorhombic space group Cmcm and are part of a well-known family of fluorite-related oxides of stoichiometry Ln(3)MO(7). This structure contains rare earth cations in two different coordination environments, 8-fold pseudocubic and 7-fold pentagonal bipyramidal, and contains Ru(V) cations that are octahedrally coordinated. The RuO(6) octahedra are trans vertex-sharing to yield chains oriented along the c-axis. Upon cooling, single crystals of Sm(3)RuO(7) and Eu(3)RuO(7) undergo a structural transition at 190 and 280 K, respectively, from space group Cmcm to P2(1)nb. The structure transition results in a loss of lattice centering, a doubling of the b-axis, a distortion of the vertex-shared Ru-O chains, and a reduction in the coordination of one of the rare earth cations from 8-fold to 7-fold. Accompanying this structural transition are anomalies in the magnetic susceptibility at about 190 and 280 K for Sm(3)RuO(7) and Eu(3)RuO(7), respectively. The structures of these low-temperature phases of Ln(3)RuO(7) have been determined for the first time and are described.     

Morphology of RuO2-TiO2 coatings and TEM characterization of oxide sols used for their preparation

Characterization of RuO(2) and TiO(2) sols of different aging times, obtained by forced hydrolysis of appropriate chloride salts, was performed by transmission electron microscopy (TEM). The aging time of TiO(2) sols was observed to affect the size of particles as well as the crystallinity of the solid phase of the sols. The surface morphology of RuO(2)-TiO(2) coatings on titanium, obtained by the sol-gel procedure using TiO(2) sols of different aging times and RuO(2) sol of fixed aging time, was investigated by scanning tunneling microscopy (STM) at three different scan sizes. The STM data indicated uniform microdistribution of the coating material (small microroughness) and an increase in nanoroughness with the aging time of the TiO(2) sol. The observed increase in real coating surface area with increasing TiO(2) particle size confirms the earlier cyclic voltammetry results.     

Synthesis and characterization of a magnetic semiconductor Na(2)RuO(4) containing one-dimensional chains of Ru(6+)

A new ternary ruthenium oxide Na(2)RuO(4) was prepared and shown to crystallize with a new structure type. Single crystal X-ray diffraction measurements reveal that Na(2)RuO(4) consists of RuO(4) chains made up of RuO(5) trigonal bipyramids by sharing axial corners. Na(2)RuO(4) is a magnetic semiconductor with a variable range hopping behavior, and its molar magnetic susceptibility chi(mol) has a broad maximum at approximately 74 K. The derivative d(chi(mol).T)/dT exhibits a peak at 37.7 K which has been confirmed by heat capacity measurement to be due to long-range antiferromagnetic ordering.