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Crossed nanosheets of transition metal oxide (TMO-NS: Co-NS, Mn-NS and Fe-NS) were synthesized by a facile hydrothermal method and employed for soot combustion in the NO/O2/N2 and O2/N2 atmosphere under gravitational contact mode (GCM). They show high catalytic activities for soot combustion due to the macroporous structure of the as-prepare catalysts increasing the soot-catalyst contact efficiency. The XRD and XPS results reveal that the active phases in the corresponding catalysts exist as Co3O4, Mn2O3 and Fe2O3, respectively. Among these catalysts, the Co-NS shows the best activity for soot combustion, especially in the presence of NO, whose catalytic activity of T50 (391 °C) and SCO2 (100%) is as good as that of the Pt/Al2O3 catalyst. The excellent performance of the Co-NS catalyst results from several factors: the highest intrinsic activity (TOF = 1.77 × 10−5 s−1); the highest redox property as revealed by H2-TPR and soot-TPR; the largest amount of active oxygen species as clarified by XPS; the highest ability of NO oxidation to NO2 supported by NO-TPO. In addition, the multiporous structure of Co3O4 nanosheets is facilitated for the mass transfer. In the O2 atmosphere, soot particulates are directly oxidized by the surface adsorbed oxygen. After introducing of NO, the soot particulates are readily oxidized by NO2 at the low temperature (

A series of CuMnCeO catalysts with 10% CuO (weight loading) and variable atomic ratios of Mn/Mn + Ce (0, 0.02, 0.05 or 0.10) were synthesized by co-precipitation and employed for CO preferential oxidation (CO PROX). After doping a small amount of manganese into ceria, the catalysts show improved catalytic performance as compared with the undoped one, especially the catalyst with the Mn/Mn + Ce atomic ratio of 0.05 (CMC-0.05) which displays the lowest temperatures for half CO conversion (T50 = 73 °C) and full CO conversion (T100 = 108 °C). In addition, it also exhibits the widest temperature window of full CO conversion (108–149 °C) and 100% selectivity of oxygen to CO2 below 117 °C. As revealed by XRD and UV-Raman, the presence of appropriate amount of Mn cannot only enhance the formation of Ce–Cu–Mn–O ternary oxide solid solution with fluorite structure, inhibiting the growth of CeO2 crystallite size, but also increase the oxygen vacancies. The results of H2-TPR and XPS indicate that the reducibility and amount of surface oxygen species of CMC-0.05 are also improved, both of which are beneficial to catalytic performance. In situ XANES results suggest that the bulk copper species still remain as Cu2+ ions below 200 °C even in H2-rich CO PROX atmosphere; however, the in-situ DRIFTS spectra indicate that during CO PROX below 120 °C the surface copper species are Cu+ ions which are regarded as the main active sites for CO PROX; above 120 °C Cu0 species appear, which enhance H2 oxidation, decreasing the oxygen to CO2 selectivity.

Samarium hydroxide (Sm(OH)3) is an important samarium compound with many potential applications in electronics, optics and catalysis. Based on a facile hydrothermal method assisted by oleic acid surface modifications we synthesized Sm(OH)3 nanocrystals with various morphologies. In this system, by adding the oleic acid surfactant both crystallization and grain size of nanocrystals can be tuned. Furthermore, the paramagnetic resonance and magnetic measurements point out that rod-like Sm(OH)3 samples are non-magnetic, while Sm(OH)3 disc-like samples exhibit weak ferromagnetism. The correlation between magnetism and morphology in Sm(OH)3 nanocrystals is associated with the surfactant-induced surface modification as well as with the changes in the localization of electrons in Sm 5d orbitals, in agreement with X-ray absorption spectroscopy data.

Ce-substituted ternary oxide catalysts ZnAlCex were prepared and employed in dimethyl ether steam reforming (DME SR) to produce hydrogen. XRD, XAFS (XANES & EXAFS), H2O-TPD, CH3OH-TPD and TPSR techniques were used for catalyst characterization. It is found that the catalytic performance of these catalysts is dependent on Ce content. The catalyst containing 20 wt% CeO2 exhibits the best catalytic performance. Its calculated TOF (0.034 s−1) is nearly three times to that of ZnAlO. The kinetic results reveal that the addition of 20 wt% CeO2 to ZnAlCex greatly decreases the apparent activation energy (Ea) of DME SR, due to the formation of new reaction sites such as Ce4+–O–Zn2+ linkages. XRD and EXAFS analyses indicate that Ce addition can not only decrease the crystallite size of ZnO and ZnAl2O4, but also tune the relative contents of them. The results of H2O-TPD and CH3OH-TPD show that Ce addition can lower H2 desorption temperature, which accounts well for the better catalytic performance of ZnAlCex. It is worth noting that the Zn-based catalysts display much lower CO selectivity than the Cu-based one, especially the Ce-substituted ZnAlCex. Start-off durability tests demonstrate that this series of catalysts also possess high catalytic stability.

A series of hydrotalcite-derived multicomponent oxide catalysts Co2.5Mg0.5Al1-x%La-x%O (denoted as CMALa(x), x=0, 5, 8, 10 or 15) with different La contents were synthesized by co-precipitation, and employed for catalytic soot combustion and NOx storage at lean condition. It is found that the La-substituted catalysts are more active than the one without La for soot combustion and NOx storage. Among all the catalysts CMALa(x), CMALa(10) (x=10) exhibits the highest catalytic performance, showing the largest NOx storage capacity (300 mu mol/g) and the lowest temperature for the maximal soot oxidation rate (T-m = 388 degrees C). The results of H-2-TPR and O-2-TPD indicate that the La-substitution can enhance the redox properties and increase the amount of surface lattice oxygen species of the catalysts. The results of soot combustion kinetics show that the apparent activation energy of CMALa(10) is the lowest (92.75 kJ/mol). Based upon the catalytic performance and in situ DRIFTS characterization, a nitrate and/or NO2 enhanced soot combustion mechanism over CMALa(10) was proposed. It is revealed that at low temperature the stored nitrate can directly promote soot ignition, while at high temperature the NO2 species arising from NO oxidation or nitrate decomposition act as the main active species for soot combustion. (C) 2014 Elsevier B.V. All rights reserved.

A series of nonplatinic ceria-based oxides supported catalysts LaCoO3/K2CO3/S (S=CeO2, Ce0.75Zr0.25O2 or 5%Y/Ce0.75Zr0.25O2) were prepared by successive impregnation and employed for lean-burn NOx trapping. It is found that the doping of Zr or YZr into CeO2 facilitates the formation of CeZrO binary or YCeZrO ternary solid solutions, increasing the specific surface area and improving the redox property of ceria. The results of EXAFS and H2-TPR reveal that the LaCoO3 in the solid solution supported catalysts possesses higher dispersion and better reducibility than that in CeO2 supported one. The result of O2-TPD shows that the surface active oxygen species are remarkably increased after loading LaCoO3 on the supports. The YCeZrO ternary solid solution supported catalyst containing 5 wt % K2CO3 exhibits the best performance for NO oxidation and reduction at 350 °C, showing a high NO-to-NO2 conversion (66.5%) at lean condition, and a very high NOx reduction percentage (98.2%) and an extremely high NOx-to-N2 s...

The release of nanoparticles (NPs) to the environment poses an increasing potential threat to biological systems. This study investigated the phytotoxicity and accumulation of copper oxide (CuO) NPs to Elsholtzia splendens (a Cu-tolerant plant) under hydroponic conditions. The 50% effective concentration (EC50) of CuO NPs to E. splendens was about 480 mg/L, implying the tolerance of E. splendens to CuO NPs. The Cu content in the shoots treated with 1000 mg/L CuO NPs was much higher than those exposed to the comparable 0.5 mg/L soluble Cu and CuO bulk particles. CuO NPs-like deposits were found in the root cells and leaf cells. Cu K-edge X-ray absorption near-edge structure analysis further revealed that the accumulated Cu species existed predominantly as CuO NPs in the plant tissues. All these results suggested that CuO NPs can be absorbed by the roots and translocated to the shoots in E. splendens.

A series of MnOx-NiO composite oxide catalysts were prepared by co-precipitation method and used in the catalytic combustion of lean methane at low temperature. Compared with the corresponding single NiO and MnOx oxides, the MnOx-NiO composite oxide with proper composition exhibits much higher catalytic performance in the lean methane oxidation. XRD and HRTEM results demonstrate that MnOx-NiO is in the form of a Ni-Mn-O solid solution. XAFS and XPS results indicate that the content of manganese in MnOx-NiO has a significant influence on the oxidation state of manganese and the crystal defect of nickel oxide. MnOx-NiO catalyst with an atomic Mn/(Mn + Ni) ratio of 0.13 is provided with abundant highly dispersed manganese species of higher valence (Mn4+) and higher coordination number as well as certain nickel vacancies, due to the strong interaction between Ni and Mn species. H-2-TPR and O-2-TPD results show that the MnOx-NiO composite oxide exhibits better reducibility and oxygen mobility than NiO. All these characterizations suggest a prominent synergism between NiO and MnOx in the MnOx-NiO composite oxide, which contributes to its high performance in the lean methane combustion. (C) 2012 Elsevier B.V. All rights reserved.

Whether and how nanoclusters possessing a rich diversity of possible geometric configurations can transform from one structural type to another are critical issues in cluster science. Here we demonstrate an icosahedral-to-cuboctahedral structural transformation of Au nanoclusters driven by changing the chemical environment. For icosahedral Au(13) clusters protected by a mixture of dodecanethiol and triphenylphosphine ligands, solvent exchange of ethanol by hexane leads to quick selective desorption of the thiolate layers from the cluster surface. The surviving Au cores then undergo a much slower energy-minimization process via structural rearrangement, stabilized in the cuboctahedral structure and protected by triphenylphosphine in the hexane environment. In response to the dramatically changed atomic structure, the character of the electronic structure of the Au clusters is converted from semiconducting to metallic. This work addresses the structure-property correlation and its strong dependence on the chemical environment for metal nanoclusters.

A series K/Cu simultaneously substituted nanometric perovskite catalysts La1-xKxCo1-yCuyO3-delta (x = 0, 0.1; y = 0, 0.05, 0.1, 0.2, 0.3) were synthesized by citric acid complexation, which were employed for soot combustion, NOx storage and simultaneous NOx-soot removal. The physico-chemical properties of the catalysts were characterized by XRD, FT-IR, EXAFS, SEM, H-2-TPR, Soot-TPR, TG/DTA, XPS and in situ DRIFTS techniques. When K and Cu are simultaneously introduced into LaCoO3, soot combustion is largely accelerated, decreasing the characteristic temperature (T-m) corresponding to the maximal soot combustion rate at least 80 degrees C; moreover, NOx reduction by soot is also remarkably facilitated. Among all the catalysts La0.9K0.1Co0.9Cu0.1O3-delta shows the lowest T-m of 360 degrees C, the highest NOx storage capacity (NSC) of 284 mu mol g(-1) and the largest NOx reduction percentage of 32%; for soot combustion, it also exhibits the lowest activation energy (80.04 kJ mol(-1)). The XPS and Soot-TPR results reveal that the catalyst La0.9K0.1Co0.9Cu0.1O3-delta possesses more active and larger amount of surface oxygen species (O-2(-) and O-), more tetravalent cobalt ions and better reducibility than others, which determines its better catalytic performance. Based on in situ DRIFTS and other characterization results, the potential mechanisms for soot combustion, NOx storage and simultaneous NOx-soot removal are proposed. (c) 2012 Elsevier B.V. All rights reserved.

A series of hydrotalcite-derived K/MnMgAlO catalysts were synthesized by co-precipitation and impregnation methods. Their catalytic performances for soot combustion, NOx storage and simultaneous soot-NOx removal were evaluated, respectively. Techniques of TG/DTA, BET, XRD, EXAFS, and in situ DRIFTS were employed for catalyst characterization. The catalyst K/Mn1.5Mg1.5AlO containing 7.5 wt% K shows not only the highest soot oxidation rate of 58.0 mu gs(-1) per gram catalyst, but also the maximal NOx reduction percentage of 26.9%. Over the catalysts containing K less than 10 wt%, the soot combustion follows oxygen spillover mechanism, while over those containing more than 10 wt% K it follows a different mechanism involving the participation of potassium nitrate species. In situ DRIFTS results indicate that introduction of proper amount of K can facilitate the formation of monodentate nitrate, which shows higher reactivity with soot than nitrite, chelating bidentate nitrate and ionic nitrate species. In the catalysts promoted by K, a new phase namely K2Mn4O8 was identified, which is highly active for soot combustion and NOx reduction by soot. (C) 2012 Elsevier B.V. All rights reserved.

We report the discovery of a potentially useful superconcentrated HCl at ambient temperature and pressure by using a simple surfactant-based reversed micelle system. Surprisingly, the molar ratios of H(+) to H(2)O (denoted as n(H+)/n(H2O)) in superconcentrated HCl can be larger than 5, while the maximum achievable n(H+)/n(H2O) value for conventional saturated HCl aqueous solution (37 wt %) is only about 0.28. Furthermore, both NMR and FT-IR results indicate that a significant amount of HCl remains in the molecular form rather than being ionized into H(+) and Cl(-). The superconcentrated HCl may promote some organic reactions that are not feasible by using conventional 37 wt % HCl solution. For example, addition reaction between C═C and HCl occurs in superconcentrated HCl solution without using catalysts.

Microbe–mineral interactions play an important role in affecting geochemical transformations of heavy metals in the soil environment. The formation of metal sulfide, which is mediated by sulfate-reducing bacteria (SRB) through contributing to sulfate reduction is an important pathway for heavy metal stabilization in anoxic soil. In oxic rice rhizospheres, there are abundant sulfur oxidizing bacteria (SOB) which can enhance sulfur oxidation and hence the availability of heavy metals, resulting in the uptake of such metals by the plant and a potential risk to human health. In this study, the potential existence of SRB in oxic rice rhizospheres, their contribution to sulfate reduction, and potential to reduce the availability of heavy metal was investigated. PCR-DGGE fingerprinting and real-time PCR results showed increasing numbers of SRB with Pb addition, which corresponded with increases in soil pH and reduction in Eh, suggesting the enhancement of sulfur reduction and SRB activity. Sulfur K-edge XANES, which characterized sulfur speciation in situ, revealed reduced states of sulfur. The SRB mediated the sulfate reduction and contributed to the formation of reduced sulfur which interacted with Pb, leading to the formation of stable metal sulfide and reduction of Pb availability. In return, acclimated SRB populations developed in Pb-polluted conditions. Hence stabilization of reduced sulfur by Pb enhanced the activity of SRB and sulfate reduction in rice rhizosphere.

A novel iron titanate catalyst prepared by conventional co-precipitation method showed excellent activity, N-2 selectivity and H2O/SO2 durability in the selective catalytic reduction (SCR) of NO with NH3. The influence of precursors and preparation methods on the catalyst structure and activity was comprehensively investigated. Iron titanate catalyst prepared using titanium sulfate as Ti precursor was favorable for the high activity and selectivity, comparing with that using titanium tetrachloride as precursor and Fe2O3/TiO2 loaded type catalyst. Especially, the best iron titanate catalyst showed good activity in a temperature window of 200-350 degrees C with the NOx conversion above 90% in the absence of H2O, which was 50-150 degrees C lower than those of other known Fe-based catalysts. Iron titanate crystallite with specific Fe-O-Ti structure was found to be the main active phase. The interaction between iron and titanium species in atomic scale led to an enhancement of oxidative ability of Fe3+, which was beneficial to the SCR reaction. (C) 2010 Elsevier B.V. All rights reserved.

Quaternary chalcogenide Cu2ZnSnSe4 (CZTSe) is a promising wide band-gap p-type thermoelectric material. The structure and thermoelectric properties of lead substituted Cu2ZnSn1-xPbxSe4 are investigated. Lead primarily exists in the framework of PbSe as demonstrated by x-ray diffraction and calculation of x-ray absorption near-edge structure spectroscopy. The second phase distributes at the boundaries of CZTSe with thickness in several hundreds of nanometer. With appropriate grain boundary engineering, the enhancement of power factor and a decrease of thermal conductivity can be achieved simultaneously. As a result, a maximum figure of merit zT of 0.45 is obtained for the sample with x=0.02 at 723K.

In this paper, we have investigated the formation of the third-phase in tertiary amine (N235)-PtCl62−-HCl system and the microscopic phase structural evolution of platinum-loaded organic phases before and after the occurrence of the third-phase. The third-phase is characterized by various spectroscopic techniques, and the small angle X-ray scattering (SAXS) experiments demonstrate the appearance of nano-aggregates, i.e., water-in-oil reversed micelles, in the third phase. The experimental results indicate that (1) formation of the third phase is related to the aggregation behaviors of nano-reversed micelles in which a super-concentrated hydrochloric acid formed with the H+ to H2O molar ratio being much higher than that of the conventional 37 wt% saturated hydrochloric acid. (2) The occurrence of the super-concentrated HCl results in a great amount of H+ and Cl− ions enriched and confined within the nano-water pools of W/O reversed micelles in third phase. Therefore, the coordination behaviors of platinum complex ions in that super-concentrated hydrochloric acid are very different from their corresponding behaviors in bulk aqueous solutions. It is possible that H+ ions participate in the formation of such complexes as HmPtCl6z+ in the super-concentrated hydrochloric acid. (3) The relative contents of various HmPtCl6z+ complexes are different corresponding to the H+ ion concentrations in confined nano-water pools. The association ability of the acidified tertiary amine N235 molecules (R3NH+) with various HmPtCl6z+ complexes plays an important role in affecting the platinum extraction behaviors.

A series of K-promoted hydrotalcite-derived CoMgAlO catalysts were synthesized by coprecipitation. Their catalytic performance for soot combustion, NOx storage and simultaneous soot–NOx removal was evaluated, respectively. The techniques of TG/DTA, BET, XRD, EXAFS, XPS and in situ DRIFTS were employed for catalyst characterization. When K is added to the catalyst CoMgAlO, soot combustion is largely accelerated, with the temperature ( T m ) for maximum soot conversion lowered by at least 50 °C. Moreover, the NOx reduction by soot over the catalysts calcined at 500–700 °C is also facilitated. The K-containing catalyst calcined at 600 °C shows not only the highest soot combustion rate, but also the maximum NOx reduction percentage of 32%, which is attributed to its high surface K/Co atomic ratio and the strong interaction between K and Co. In situ DRIFTS results reveal that NO is readily oxidized to NO 2 and stored as nitrates over K-promoted catalysts, which could be reduced by soot more efficiently. Based on these investigations, a reaction pathway for soot combustion, NOx storage and simultaneous soot–NOx removal is proposed.

Phytolacca acinosa Roxb. is a Mn hyperaccumulating plant. In the present study, the chemical forms of Mn in the leaves of P. acinosa were investigated using chemical analyses and X-ray absorption spectroscopy (XAS). P. acinosa plants were grown hydroponically with 2 mM Mn for 28 days. About 80% of the Mn in the leaves of P. acinosa was found in the supernatant fraction after centrifugation at 20,000g for 45 min. The supernatant fraction was then used to identify the chemical forms of Mn. Gel filtration analysis (Sephadex G-10) showed that oxalate and Mn appeared in the same fraction of the supernatant and the molar ratio of oxalic acid to Mn was 1.12, indicating that there was sufficient oxalic acid in P. acinosa leaves to complex Mn. XAS was employed to investigate the chemical species of Mn in leaves of P. acinosa. Results showed that Mn in leaves was bivalent and almost 90% of the total Mn was Mn-oxalate. The oxalate concentration in the leaves of P. acinosa was not affected by increasing Mn concentration in the solution, suggesting that oxalate biosynthesis was not induced by Mn.

Crack-free GaN films have been achieved by inserting an Indoped low-temperature (LT) AlGaN interlayer grown on silicon by metalorganic chemical vapor deposition. The relationship between lattice constants c and a obtained by X-ray diffraction analysis shows that indium doping interlayer can reduce the stress in GaN layers. The stress in GaN decreases with increasing trimethylindium (TMIn) during interlayer growth. Moreover, for a smaller TMIn flow, the stress in GaN decreases dramatically when In acts as a surfactant to improve the crystallinity of the AlGaN interlayer, and for a larger TMIn flow, the stress will increase again. The decreased stress leads to smoother surfaces and fewer cracks for GaN layers by using an In-doped interlayer than by using an undoped interlayer. In doping has been found to enhance the lateral growth and reduce the growth rate of the c face. It can explain the strain relief and cracks reduction in GaN films. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Elsholtzia splendens is a Cu-tolerant plant growing in copper mine areas in the south of China. In this study, X-ray absorption spectroscopy (XAS) was used to investigate the Cu speciation and biotransformation in E. splendens with 300 μM Cu treatment from 10 days to 60 days. The results showed that 300 μM Cu was phytotoxic to E. spendens. The Cu K-edge X-ray absorption near edge structure (XANES) revealed that most copper in roots, stems and leaves exists as divalent Cu. Cu speciation changed depending on the treatment time, but there was no unidirectional trend in roots, stems, and leaves. The percentages of potential Cu ligands in all samples were estimated by fitting the XANES spectra with linear combinations. Most Cu in roots, stems and leaves was bound with cell wall and histidine (His)-like ligands, while a minor proportion of the Cu was bound to oxalate and glutathione-like ligands. The fitting results of Cu K-edge extended X-ray absorption fine structure (EAXFS) showed that nitrogen/oxygen (N/O) ligands were dominant in roots, stems and leaves of the plant, while S ligands were rare. All these results suggest that Cu bound by N/O ligands plays a key role in Cu detoxification of E. splendens, and a role for classical metal-detoxifying S ligands, such as metallothioneins and phytochelatins, in Cu detoxification of E. splendens is not supported in the present study. Due to the phytotoxicity of 300 μM Cu to E. splendens, the question of whether S ligands play a significant role in Cu detoxification in E. splendens exposed to lower levels of Cu should be further studied.

Crossed Fe2O3 nanosheets supported cobalt oxide nanoparticles on three-dimensionally macroporous nickel foam substrate (xCo/Fe-NF) was designed and successfully prepared through a facile hydrothermal and impregnation route. These catalysts showed high catalytic soot combustion activities under self-capture contact mode. The three-dimensional macroporous structures of Ni foam and the crossed Fe2O3 nanosheets constituted macroporous voids can greatly increase the contact efficiency between soot particulates and catalysts. The interaction between Co and Fe facilitated the activation of the Fe–O bond and increased the amounts of active oxygen species, thus improving the redox property of the catalysts. The 0.6Co/Fe-NF catalyst exhibited the highest turnover frequency (TOF) for soot combustion, which is in good accordance with the largest amount of active oxygen species. Based upon the catalytic performance and multiple characterization results, two reaction pathways for soot oxidation are identified, namely, the direct oxidation by the activated oxygen species via oxygen vacancies and the NOx-aided soot oxidation.

The recent discovery of the magnesium diboride superconductor, a system characterized by a remarkably high transition temperature ( T c = 39 K ), has renewed interest towards experimental and theoretical research of the superconductivity in isostructural systems, such as transition-metal diborides. Here we present an X-ray-absorption fine-structure investigation in AlB 2 -type 4d transition-metal diborides TMB 2 (TM=Y, Zr, Nb) at the transition-metal K-edge. The vibrational behavior of these transition-metal diborides has also been investigated by analyzing the extended X-ray-absorption fine-structure (EXAFS) spectra. The change of the bond length and Debye–Waller factors of TM–B, TM–TM (in-plane) and TM–TM (out-plane) with the covalent radii of the transition-metal atoms has been shown. Data clearly demonstrate that the chemical stability is in the following order for the 4d transition-metal diborides: ZrB 2 >NbB 2 >YB 2 . The chemical stability of YB 2 must be much less than that of the two other compounds. It suggests that the species difference of the transition metals influences the vibrational behavior of TM–B and TM–TM bonds. In particular, a clearly different behavior of the vibration is observed for the transition-metal atoms in and out of plane. The results suggest the importance of the metal atoms in the diborides for superconductivity of these compounds and an intimate relationship between the local atomic displacements and the superconductivity.

ZrO2-doped CuZnO catalyst prepared by successive-precipitation method was investigated by ICP-AES, BET, TEM, XRD, EXAFS, H-2-TPR and CO/CO2 hydrogenation. The active phase of copper in CuZnO catalyst prepared by co-precipitation method was well-crystallized. The presence of ZrO2 led to a high copper dispersion, which was distinctive from CuZnO. Though the activity for carbon monoxide hydrogenation was little lower than that of CuZnO catalyst, ZrO2-doped CuZnO catalyst showed much higher activity and selectivity towards methanol synthesis from carbon dioxide hydrogenation. Moreover, ZrO2-doped-CuZnO catalyst showed high performance for methanol synthesis from CO2-rich syngas. (c) 2006 Elsevier B.V. All rights reserved.

The mesoporous La-Co-Zr-O catalyst with the atomic ratio of La + Co/La + Co + Zr = 0.5 was prepared by citric acid complexation-organic template decomposition method, using the mixture of nonionic-p-octyl polyethylene glycol phenyl ether (OP) and cationic cetyltrimethyl-ammonium bromide (CTAB) as co-templates (LCZ-OP/CTAB-0.5). The results of BET and pore size distribution show that this sample possesses much bigger specific surface area (117.6m(2)/g) than those prepared by using single template CTAB (96.6m(2)/g, LCZ-CTAB) or by using conventional co-precipitation method (21.6 m(2)/g, LCZ-CO). Both the samples obtained from single template CTAB and from the co-templates of OP and CTAB show very uniform mesoporous pore diameter (3.5-4.3 nm). The structural characterization results of XRD, XPS and Co K-edge EXAFS indicate that the highly dispersed Co3O4 crystallite should be the main active phase for CO oxidation. The crystal sizes Of Co3O4 crystallites in LCZ-CTAB and LCZ-OP/CTAB-0.5 are 23.4 and 32.5 nm, respectively, which are much smaller than that in LCZ-CO (56.8 nm). The catalytic activity evaluation shows that the sample prepared by co-templates decomposition possesses much better activity for CO oxidation, especially the low temperature oxidation activity. However, the activity sequence of the samples is not the same as the crystal size of Co3O4 phase. On the contrary, the reducibility of bond Co-O and the reduced amount Of Co3O4 phase below 500 degrees C for the samples are well correlated with their activity law, which should be a crucial factor for the oxidation performance of the samples. (c) 2006 Elsevier B.V. All rights reserved.

The structure and catalytic performance of CuMnZrO2 and Fe-CuMnZrO2 catalysts, which were calcined at different temperature, were investigated by BET, XRD, N2O-titration, XANES, EXAFS and TPR. It was found that the calcination temperature strongly influenced the interaction between the active species and support and hence the structure and catalytic performance. Low calcination temperature yielded poorly crystallized catalysts and favored the formation of a Cu(OH)(2)-like structure. The presence of iron could suppress crystallization of amorphous zirconia and increased the dispersion of copper due to the iron-zirconia interaction within the rise of calcination temperature from 623 to 873 K. However, the addition of iron resulted in the decrease of catalytic activity and selectivity. This could be explained by strong iron-zirconia interaction. It led to the decrease of copper-zirconia interaction, which was responsible for the methanol synthesis, and the decrease of copper-iron interaction, which was responsible for the formation of higher alcohols. (c) 2005 Elsevier B.V. All rights reserved.

gamma-Alumina-supported beta-Mo2N0.78 catalyst was synthesized by the temperature-programmed nitriding reaction and tested to determine its catalytic activity and selectivity during the hydrodesulfudzation (HDS) of dibenzothiophene. The results indicated that the conversion increases with reaction temperature and hydrogen pressure. And increasing the hydrogen pressure results in more hydrogenation, but increasing reaction temperature can improve the two parallel pathways of direct desulfurization and hydrogenation desulfurization at same degree. Sulfur can replace the surface oxygen of passivated nitride in the HDS reaction although the bulk structure is preserved. (C) 2004 Elsevier B.V. All rights reserved.

The effect of iron on the structural and catalytic properties of CuMnZrO2 catalysts used for higher alcohols synthesis has been investigated by several techniques (BET, X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), temperature program reduction (TPR), CO-FTIR and CO hydrogenation). It was found that the presence of iron resulted in substantial changes in both structure properties and catalytic performance. The copper dispersion increased and the catalyst stabilization was improved. The role of iron was dependent on the method of catalyst preparation. The co-precipitation method produced highly dispersed copper species, which favored the synthesis of methanol and branched alcohols. However, the wetness impregnation method gave rise to highly dispersed copper and copper-iron phase, which showed a good performance for synthesis of straight-chain alcohols. Such differences in the performance of catalysts could be attributed to the extent of iron oxide-support interaction, which led to the presence of metallic iron phases in the reduced catalyst. (C) 2004 Elsevier B.V. All rights reserved.

CO2 reforming of CH4 was carried out with and without steam over a Ni/CeO2–ZrO2–Al2O3 catalyst. The catalytic performance, amount of carbon deposit and the EXAFS of the Ni K-edge of samples were measured. The results show that when the catalyst is used for CO2 reforming of CH4 without the addition of steam, the catalyst gradually deactivates, however, addition of a small amount of steam to the feed gas can significantly inhibits the deactivation, which is due to the great suppression of coke formation on the catalyst during the reaction. The EXAFS result shows that, maybe due to the penetration of more carbon atoms into the Ni lattice, the coordination number of the nearest Ni–Ni of the sample after the reaction without steam reduces more than that of samples after the reaction with a small amount of steam in the feed gas.

The dispersion process and structure of impregnated CuO/ZrO2 systems were studied by x-ray diffraction (XRD) and extended x-ray absorption fine structure (EXAFS). The results showed that, after being calcined at 773 K, monolayer dispersed cupric nitrate decomposed into monolayer dispersed cupric oxide on zirconia's surface. The dispersion threshold of CuO was related to its precursor, cupric nitrate. The surface-dispersed Cu nearest coordination structure changed into about five equally long Cu–O bonds. Copyright © 2003 John Wiley & Sons, Ltd.

By analysis of the extended X-ray absorption fine structure (EXAFS) of the Mo K-absorption edge, the structural information of both oxidic and nitrided Mo catalysts supported on zeolites was obtained. The supported MoO 3 samples show three peaks in the radial structure function (RSF). The first two peaks represent the nearest Mo–O coordination shell and the ratio of the first peak to the second one is much larger than that of the MoO 3 crystallites, which suggests that the MoO 3 supported on zeolites has a compact structure than the unsupported one. Three peaks on the RSF of γ-Mo 2 N represent one Mo–N and two Mo–Mo coordination shells, respectively. This is in good agreement with the face-centered cubic model. Calculation from X-ray diffraction data and EXAFS spectra reveals that the N atoms in γ-Mo 2 N lengthen the distance between Mo atoms and weaken the Mo–Mo bond. Supported Mo 2 N samples give out nearly the same RSFs as the γ-Mo 2 N and only the peak corresponding to Mo–N shell is weak. This suggests the supported Mo 2 N has more configurational disorder.

Activities of ferrous sulfate based catalysts impregnated on two Chinese coals were studied in coal liquefaction, and compared with an impregnated iron sulfide catalyst. Chemical forms and particle size distribution of the impregnated ferrous sulfate based catalysts were determined using EXAFS, XRD and SAXS techniques. The impregnated ferrous sulfate shows significant activity in the liquefaction of bituminous coals, but is less active than the impregnated iron sulfide catalyst. Addition of Na2S or urea to the ferrous sulfate in the impregnation process increases the coal conversion to the level of the impregnated iron sulfide catalyst. Addition of Na2S does not significantly promote the formation of iron sulfide on coal surface as usually believed. The iron impregnated on the coal surface existed mainly in the form of γ-FeOOH regardless of the forms of iron and the promoters. The most probable diameter of the impregnated ferrous sulfate based catalyst determined by SAXS is around 40–50 A.

The optical properties of poly(phenylenevinylene) (PPV)/TiO2 nanocomposites, prepared from mixtures of PPV precursor and titanium butoxide ethanol solution in a sol–gel process, are investigated by UV–VIS, FT-IR, PL spectroscopy and TEM. The TEM images showed that the TiO2 nano-aggregates took the form of a sphere and finally ellipsoid with an alignment, as the content of TiO2 increased. FT-IR spectra indicated that the titanium butoxide hydrolyzed to form Ti organic compound, which can result in the alignment structure of TiO2 nanoparticles; at the same time, PPV in TiO2 matrix had the trans-PPV configuration. PL spectra revealed that the light emission of the PPV/TiO2 nanocomposites was from PPV, and the relative intensity of the vibrant components changed with the formation of the TiO2 alignment structure. These phenomena suggest that the TiO2 matrix can form confined environments to control PPV molecular aggregate states and further effect the optical property of PPV.

SO2 shows a significant promoting effect on the activity of V2O5/AC catalyst for NO reduction with ammonia at low temperatures (180–250°C). In the present study, the mechanism of the SO2 promotion was studied. It was found that the promoting effect of SO2 on the catalytic activity is due to the formation of a sulfate species on the catalyst surface. The sulfate species is linked to carbon surfaces other than vanadium or mineral surfaces. There is a synergetic role between carbon and V2O5 for the formation of surface sulfate species. A possible mechanism is proposed. SO2 is adsorbed and oxidized by oxygen to SO3 on the vanadium surface, and the formed SO3 shifts to the carbon surface and converts into sulfate species. The formed sulfate species acts as a new acid site, improves significantly the NH3 adsorption, and hence promotes the activity of the catalyst. During the reaction in the presence of SO2 at low temperatures, the sulfate species stays on the catalyst surface, while the ammonium ions react with NO continuously to avoid the formation and deposition of excess ammonium sulfate salts on the catalyst surface.

The microstructures of loaded organic phases of three quaternary amine solvent extraction systems for gold, which were N263–xylene, N263–tributyl phosphate (TBP)–dodecane and N263–2-ethylhexanol (isooctanol)–dodecane (N263-trialkylmethylammonium chloride; alkyl=C8–C10), were studied by Fourier transform infrared (FTIR) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. According to the EXAFS results, it was found that the gold coordination environment was the same before and after extraction. However, the C3N stretching vibrations of Au(CN)2- in the three systems differed greatly. The second derivative spectra of C3N stretching bands of Au(CN)2- were also found to be different. In order to explain the differences in the IR characteristics of C3N in the three extraction systems, three microstructure models are proposed. For the N263–xylene system, the model is a simple ion pair. For the other two systems with a modifier (TBP and isooctanol), the models are two supramolecular structures based on hydrogen bonding between the modifier and Au(CN)2-. Some related work such as on the hydration of acetonitrile and the fine structure of C3N in solid KAu(CN)2 was also performed in order to offer additional supporting evidence for the reliability of the proposed models.

The concentration ranges of As and Sb in six Late Permian high-arsenic coals collected from Xingren and Xingyi, Guizhou Province are 94.1 μg · g-1-3.2% and 8.1 μg · g-1-120 μg · g-1, respectively. Based on the mineralogical analysis, no arsenic and arsenic-bearing minerals are detected in these samples and arsenic occurs in coal macerals. By extended X-ray absorption fine structure(EX-AFS) spectroscopy, we have found that arsenic in these high-arsenic coal samples coordinates with oxygen; the coordination number of As with oxygen for these samples is 4 except one sample(H9) for which the coordination number of As is 3. Therefore, arsenic in these high-arsenic coals does not occur in sulfide minerals, but occurs in arsenate or arsenite phase, and the preponderance of As is in arsenate of As5+.

Mercury uptake was induced in two cultivars of Brassica juncea under field conditions using thiosulfate. Analysis was conducted to better understand the mechanism of uptake, speciation of mercury in plants, and redistribution of mercury in the soil. Plant mercury and sulfur concentrations were increased after thiosulfate treatment, and a linear correlation between mercury and sulfur was observed. Mercury may be absorbed and transported in plants as the Hg-thiosulfate complex. The majority of mercury in treated plant tissues (two cultivars) was bound to sulfur in a form similar to β-HgS (66-94%). Remaining mercury was present in forms similar to Hg-cysteine (1-10%) and Hg-dicysteine (8-28%). The formation of β-HgS may relate to the transport and assimilation of sulfate in plant tissues. Mercury-thiosulfate complex could decompose to mercuric and sulfate ions in the presence of free protons inside the plasma membrane, while sulfide ions would be produced by the assimilation of sulfate. The concomitant presence of mercuric ions and S(2-) would precipitate β-HgS. The mercury concentration in the rhizosphere decreased in the treated relative to the nontreated soil. The iron/manganese oxide and organic-bound fractions of soil mercury were transformed to more bioavailable forms (soluble and exchangeable and specifically sorbed) and taken up by plants.

Reactive adsorption desulfurization (RADS) of a model oil n -nonane containing dibenzothiophene (DBT) was conducted over a Ni/ZnO adsorbent; the evolution of Ni/ZnO adsorbent structure during desulfurization was monitored by in situ X-ray absorption spectroscopy (XAS). The reaction mechanism under different atmospheres and the role of hydrogen in the desulfurization were investigated. The results indicated that the desulfurization processes under nitrogen and hydrogen are different in the reaction mechanism. In nitrogen, the desulfurization over Ni/ZnO is achieved through physical and chemical adsorption; a severe decrease in the desulfurization activity of Ni/ZnO is observed with the time on stream and the desulfurization capacity is very low. In hydrogen, the desulfurization turns to be a reactive adsorption process and Ni/ZnO exhibits a high desulfurization activity and capacity. Hydrogen plays an important role in the RADS; it facilitates the decomposition of DBT on active Ni species, the formation of Ni 3 S 2 , and thereafter the transfer of sulfur to ZnO. Metallic Ni as the active nickel species is preserved until most of ZnO is converted to ZnS. On the basis of these observations, a possible sulfur transfer mechanism for the RADS is then proposed.

Annealing crystallization of ultrafine NiB amorphous alloy prepared by the chemical reduction method was studied by DTA, XRD and XAFS techniques. The XRD and XAFS results have revealed that the crystallization process of ultrafine NiB amorphous alloy proceeds in two steps. First, ultrafine NiB amorphous alloy is crystallized to form metastable nanocrystalline Ni3B at an annealing temperature of 325°C. Second, the nanocrystalline Ni3B is further decomposed into crystalline Ni at 380°C or higher temperature, the local structure around Ni atoms in resultant product is similar to that in Ni foil. It was found that the catalytic activity of nanocrystalline Ni3B for benzene hydrogenation is much higher than that of ultrafine NiB amorphous alloy or crystalline Ni. The result indicates that the active sites of nanocrystalline Ni3B for benzene hydrogenation are composed of both Ni and B with proper geometry configuration.

The hydrotalcite-based Mn(x)Mg(3-x)AlO catalysts with different Mn:Mg atomic ratios were synthesized by coprecipitation, and employed for soot combustion, NOx storage and simultaneous soot-NO(x) removal. It is shown that with the increase of Mn content in the hydrotalcite-based Mn(x)Mg(3-x)AlO catalysts the major Mn-related species vary from MnAl(2)O(4) and Mg(2)MnO(4) to Mn(3)O(4) and Mn(2)O(3). The catalyst Mn(1.5)Mg(1.5)AlO displays the highest soot combustion activity with the temperature for maximal soot combustion rate decreased by 210 degrees C, as compared with the Mn-free catalyst. The highly reducible Mn(4+) ions in Mg(2)MnO(4) are identified as the most active species for soot combustion. For NO(x) storage, introduction of Mn greatly influences bulk NO(x) storage, with the adsorbed NO(x) species varying from linear nitrites to ionic and chelating bidentate nitrates gradually. The coexistence of highly oxidative Mn(4+) and highly reductive Mn(2+) in Mn(1.0)Mg(2.0)AlO is favorable to the simultaneous soot-NO(x) removal, giving a NO(x) reduction percentage of 24%. In situ DRIFTS reveals that the ionic nitrate species are more reactive with soot than nitrites and chelating bidentate nitrates, showing higher NO(x) reduction efficiency.

The arsenic (As) hyperaccumulators, Pteris vittata and Pteris cretica and an As-tolerant plant Boehmeria nivea, were selected to compare the toxicity, uptake, and transportation of inorganic arsenate (As(V)) and its methylated counterpart dimethylarsinic acid (DMA). The XANES method was used to elucidate the effect of As species transformation on As toxicity and accumulation characteristics. Significantly higher toxicity and lower accumulation of DMA than inorganic As V) was shown in the As hyperaccumulators and the As-tolerant plant. Reduction of As(V) was commonly found in the plants. Arsenic complexation with thiols, which have less mobility in plants and usually occur in As-tolerant plants, was also found in rhizoids of P. cretica. Plants with greater ability to form As-thiolate have lower ability for upward transport of As. Demethylation of DMA occurred in the three plants. The DMA component decreased from the rhizoids to the fronds in both hyperaccumulators, while this tendency is reverse in B. nivea.

Although the Gd ion in Gd@C(82) has been shown to lie above the C-C bond on the C(2) axis as an anomalous structure from the MEM/Rietveld analysis, the present XANES study reveals that it lies above the hexagon on the C(2) axis as a normal structure, and Gd oscillates around its equilibrium position with an amplitude increasing with temperature increase.

Our findings reveal an ordered–disordered phase transformation in LiNi0.5Mn1.5O4 triggered by sucrose. Extended X-ray absorption fine structure spectroscopy (EXAFS) was used to determine the local structure in sucrose-treated LiNi0.5Mn1.5O4. It was found that larger lattice strain in sucrose-induced disordered LiNi0.5Mn1.5O4 is attributed to Ni-site distortion.

As a representative natural porphyrin derivative, it is interesting to know the chemical form of lanthanide in chlorophyll a. We select the natural fern dicranopteris dichotoma, the most lanthanide-concentrated plant known, to isolate the chlorophyll a for our study. It is found by EXAFS that lanthanum substitutes in the magnesium position in chlorophyll and coordinates with the porphyrin ring. The lanthanum is seen to have a similar coordination structure to a sandwich-type lanthanide complex, with the La surrounded by eight nitrogen atoms from two porphyrin rings with average La-N bond length of 2.65 Å.