In situ synthesis of mixed-valent manganese oxide nanocrystals: an in situ synchrotron X-ray diffraction study

Phase transformations of materials can be studied by in situ synchrotron X-ray diffraction. However, most reported in situ synchrotron XRD studies focus on solid state/gel systems by measuring phase/structure changes during application of pressure or heat. Phase transformations during material synthesis and their applications, especially in wet chemistry processes with different media, have not drawn much attention. Here, using manganese oxides as examples, we report the successful characterization of phase transformations in in situ hydrothermal synthesis conditions by the in situ synchrotron XRD method using a quartz/sapphire capillary tube as the synthesis reactor. The results were used for better design of materials with controlled structures and properties. This method can be generally used for synthesis of manganese oxides as well as for in situ characterization of other material syntheses using hydrothermal, sol-gel, and other methods. In addition, catalytic processes in liquid-solid, gas-solid, and solid-solid systems can also be studied in such an in situ way so that catalytic mechanisms can be better understood and catalyst synthesis and catalytic processes can be optimized.     

Infrared and X-ray simultaneous spectroscopy: a novel conceptual beamline design for time resolved experiments

Many physical/chemical processes such as metal–insulator transitions or self-assembly phenomena involve correlated changes of electronic and atomic structure in a wide time range from microseconds to minutes. To investigate these dynamic processes we not only need a highly brilliant photon source in order to achieve high spatial and time resolution but new experimental methods have to be implemented. Here we present a new optical layout for performing simultaneous or concurrent infrared and X-ray measurements. This approach may indeed return unique information for example the interplay between structural changes and chemical processes occurring in the investigated sample. A beamline combining two X-ray and IR beams may really take advantage of the unique synchrotron radiation properties: the high brilliance and the broad spectrum. In this contribution we will describe the conceptual layout and the expected performance of a complex system designed to collect IR and X-ray radiation from the same bending magnet on a third-generation synchrotron radiation ring. If realized, this beamline will enable time-resolved spectroscopy experiments offering new scientific opportunities at the frontiers of science.     

Nanostructure evolution studies of bulk polymer materials with synchrotron radiation: progress in method development

The prospects of a modern analysis of nanostructure evolution during the processing of polymer materials by means of scattering from synchrotron radiation are demonstrated in examples. The beam sources have gained stability, shortages are located in beamline setups and in method development for the quantitative analysis of voluminous data sets.By using the proposed multidimensional chord distribution function (CDF) analysis method, nanostructure information from small-angle X-ray scattering (SAXS) data are extracted and visualised. The method can be automated if the beamline setup is able to deliver a full data set with simple constraints. In this case even a simultaneous data evaluation is possible (while one pattern is accumulated, the previous one is analysed). The advantages of the method are demonstrated in a study of the straining of a thermoplastic elastomer. The possibilities of an automated analysis are demonstrated in an investigation of the crystallisation behaviour of high-pressure injection-moulded polyethylene (HPIM-PE). The achievable results of nanostructure analysis of polymer materials are discussed. It is shown that the time-resolved SAXS of polymer materials studied during a transformation and analysed by the CDF method is not just a powerful tool to investigate the relationship between structure and properties of materials; the information that can be gained concerning the processes that control nanostructure evolution is equally important. In the future the enlightenment of such relationships may help to tailor polymer materials with respect to their properties and, beyond that, to improve assessments concerning their aging.     

A review on non-noble metal based electrocatalysis for the oxygen evolution reaction

In order to find a clean, efficient and sustainable new energy source that can replace fossil fuels, hydrogen energy is considered to be the most ideal choice. Electrocatalytic oxygen evolution plays a vital role in the development of hydrogen energy, promotes the research of new electrocatalysts, and is dedicated to find materials with high electrocatalytic efficiency. This article discusses in detail the major developments in OER electrocatalysts, including recently reported metal and non-metal based materials. Metal-based catalysts, although having the advantages of high catalytic activity, have disadvantages such as poor stability and low selectivity, which hinder the further application of such materials. Non-metallic based materials avoid such disadvantages and exhibit very substantial performance in overall water decomposition. This review provides useful knowledge of a well-designed OER electrocatalyst and a possible strategy for OER/HER dual-function catalytic performance for future development.     

Dense ceramic catalytic membranes and membrane reactors for energy and environmental applications

Catalytic membrane reactors which carry out separation and reaction in a single unit are expected to be a promising approach to achieve green and sustainable chemistry with less energy consumption and lower pollution. This article presents a review of the recent progress of dense ceramic catalytic membranes and membrane reactors, and their potential applications in energy and environmental areas. A basic knowledge of catalytic membranes and membrane reactors is first introduced briefly, followed by a short discussion on the membrane materials including their structures, composition and strategies for material development. The configuration of catalytic membranes, the design of membrane reaction processes and the high temperature sealing are also discussed. The performance of catalytic membrane reactors for energy and environmental applications are summarized and typical catalytic membrane reaction processes are presented and discussed. Finally, current challenges and difficulties related to the industrialization of dense ceramic membrane reactors are addressed and possible future research is also outlined.     

Vanadium phosphorus oxides,a reference catalyst for mild oxidation of light alkanes: a review

Vanadium phosphorus oxides (VPO) are very promising materials for the mild oxidation of light alkanes. This is obvious from the considerable knowledge of the physicochemistry of the VPO catalytic system for which many complementary techniques have been used. The present state of the art and the possibilities for the development, in the future, of such a family of catalysts are discussed. It is highly possible that the discovery of new industrial processes for the oxidation of alkanes will stem from the improvement of vanadium phosphorus oxide catalysts.     

Diffusion of Paraffins in Dealuminated Y Mesoporous Molecular Sieve

Mesoporous materials have been intensely studied recently, mainly as possible component for FCC (Fluid Catalytic Cracking) catalysts due to their large surface area and accessibility to large hydrocarbon molecules. It is thus of interest for the oil industry to understand the diffusion behavior of some standard molecules in these materials. Y Zeolites, usually employed in fluid catalytic cracking, can be modified by removal of aluminum atoms from the zeolitic framework to present a greater mesoporous contribution. Dealumination of Y zeolite framework is also known to improve the stability of the catalyst thus making it more suitable for the FCC operation. This study presents diffusion measurements performed with the ZLC (Zero-Length Column) method, developed in the late eighties by Eic and Ruthven (1988a, b). The ZLC method has been largely used for a number of systems, either in gas or in liquid phases. We have now applied the ZLC method for gas phase diffusion measurements of linear paraffins (C₇–C₁₀) in dealuminated Y zeolite (USY). Experimental data were obtained at different temperatures (150 to 240°C) and flow rates (40 to 120 ml/min) and correlated through a transient Fickian diffusion model.     

Sources synchrotrons au Japon: perspectives

Synchrotron radiation has become a unique tool for probing the structure of matter. It has a broad range of applications, not only in basic science (molecular and atomic physics, condensed matter physics, earth science, materials science, chemistry, molecular and cell biology, surface and interface physics, etc.) but also in medicine and in the industry (material investigation, lithography, micro-machining, drug design, etc.).With one third of the world sources, Japan leads the G-8 countries and is also the leader when it comes to “industrial sources”. Japan is not building synchrotron sources solely to support basic research, it is building them because of the diversity, importance, and potential of high-technology, industrial applications of synchrotron radiation. Each source is an investment for the future, opening new research areas and calling for technical innovations.The purpose of this paper is to offer an overview of the Japanese synchrotron radiation sources and their research activities. A special attention will be given to the development of industrial sources, as well as the application of synchrotron radiation to materials science.     

Self-assembled Nanohybrid from Opposite Charged Sheets: Alternate Stacking of CoAl LDH and MoS_2

Hybrid materials are attracting intensive attention for their applications in electronics, photoelectronics, LEDs, field-effect transistors, etc. Engineering new hybrid materials and further exploiting their new functions will be significant for future science and technique development. In this work, alternatively stacked self-assembled CoAl LDH/MoS_2 nanohybrid has been successfully synthesized by an exfoliation-flocculation method from positively charged CoAl LDH nanosheets(CoAl-NS) with negatively charged MoS_2 nanosheets(MoS_2-NS). The CoAl LDH/MoS_2 hybrid material exhibits an enhanced catalytic performance for oxygen evolution reaction(OER) compared with original constituents of CoAl LDH nanosheets and MoS_2 nanosheets. The enhanced OER catalytic performance of CoAl LDH/MoS_2 is demonstrated to be due to the improved electron transfer, more exposed catalytic active sites, and accelerated oxygen evolution reaction kinetics.     

The nature of surface barriers on nanoporous solids explored by microimaging of transient guest distributions

Nanoporous solids are attractive materials for energetically efficient and environmentally friendly catalytic and adsorption separation processes. Although the performance of such materials is largely dependent on their molecular transport properties, our fundamental understanding of these phenomena is far from complete. This is particularly true for the mechanisms that control the penetration rate through the outer surface of these materials (commonly referred to as surface barriers). Recent detailed sorption rate measurements with Zn(tbip) crystals have greatly enhanced our basic understanding of such processes. Surface resistance in this material has been shown to arise from the complete blockage of most of the pore entrances on the outer surface, while the transport resistance of the remaining open pores is negligibly small. More generally, the revealed correlation between intracrystalline diffusion and surface permeation provides a new view of the nature of transport resistances in nanoporous materials acting in addition to the diffusion resistance of the regular pore network, leading to a rational explanation of the discrepancy which is often observed between microscopic and macroscopic diffusion measurements.     

Effect of the polymer matrix on the properties of advanced composites

The relationships discussed here clearly show that for the development of composite materials a multidisciplinary approach encompassing polymer chemistry, physics, engineering and material science is necessary. The complex composition of fiber reinforced polymeric composite materials, involving the synergistic interplay of individual components, requires new methods for the development of materials, which are not solely based on the formulation chemistry of the components. In the future, resistance against the application of advanced composites must be reduced, by gaining more confidence in the performance of this new class of materials with a fundamental understanding of their properties and potential. It will thus be possible to abolish unreasonable test methods and to use design characteristics which take maximum advantage of this material class.     

Combining synchrotron-based X-ray techniques with vibrational spectroscopies for the in situ study of heterogeneous catalysts: a view from a bridge

The advantages, challenges, and future possibilities for combining synchrotron-based X-ray techniques with vibrational spectroscopies are considered in this critical review. Particular emphasis is given to (1) quantifying structure and structural change--on a wide range of length scales--in working heterogeneous catalytic systems; (2) relating that change to chemical speciation occurring at the surface of the catalyst; and (3) determining how such change relates to the overall function of the catalyst material. We will consider those resources that exist today and suggest some possible future directions yet to be ventured into or demonstrated. Lastly, we will consider how the catalysis community interacts with, and uses the resources offered by, modern synchrotron radiation facilities and whether this current relationship provides the best and most inclusive means for the exploitation of these resources in this field of research (83 references).     

Gigahertz frequency-domain fluorometry: resolution of complex decays, picosecond processes and future developments

We describe the principles, instrumentation and applications of frequency-domain fluorescence spectroscopy. This method is useful for the resolution of multi-exponential decays and complex anisotropy decays on the picosecond timescale. The present instrumentation allows measurements to 2 GHz, which has been used to measure rotational correlation times as short as 7 ps. In the future it may be possible to extend the frequency range to 10 GHz, which should allow still faster processes to be quantified. It should be emphasized that resolution of fast processes is not obtained at the expense of losing information on the nanosecond timescale. Additionally, the GHz frequency-domain measurements are performed using low excitation intensities, which do not damage the samples.     

Reaction Mechanisms in Heterogeneous Catalysis; C?H Activation as a Case Study

Heterogeneous catalysis is changing from an empirical art to an exact science. The various methods for the analysis of solids and surfaces, constantly refined by materials science and surface science, seem to be almost unlimited. The increasing availability of atomic resolution microscopy as well as synchrotron radiation allows the characterization of catalyst particles, surface structures, surface processes and surface intermediates. We have learned to determine the surface structure sensitivity of catalytic reactions. Thermodynamic and kinetic data of catalytic reactions are now determined routinely. Isotopic exchange and labeling experiments provide information about reactant-catalyst interactions. How much have we learned through these techniques about the nature or mechanism of heterogeneously catalyzed reactions? The following article attempts to summarize the progress and the problems encountered in mechanistic studies of C? H bond formation and activation in a hydrogen atmosphere as an example for the present state of the understanding of reaction mechanisms in heterogeneous catalysis.     

DIFFRACTION AND HOLOGRAPHY WITH PHOTOELECTRONS AND FLUORESCENT X-RAYS

We consider studies of the atomic and magnetic structure near surfaces by photoelectron diffraction and by the holographic inversion of both photoelectron diffraction data and diffraction data involving the emission of fluorescent x-rays. The current status of photoelectron diffraction studies of surfaces, interfaces, and other nanostructures is first briefly reviewed, and then several recent developments and proposals for future areas of application are discussed. The application of full-solid-angle diffraction data, together with simultaneous characterization by low energy electron diffraction and scanning tunneling microscopy, to the epitaxial growth of oxides and metals is considered. Several new avenues that are being opened up by third-generation synchrotron radiation sources are also discussed. These include site-resolved photoelectron diffraction from surface and interface atoms, the possibility of time-resolved measurements of surface reactions with chemical-state resolution, and circular dichroism in photoelectron angular distributions from both non-magnetic and magnetic systems. The addition of spin to the photoelectron diffraction measurement is also considered as a method for studying short-range magnetic order, including the measurement of surface magnetic phase transitions. This spin sensitivity can be achieved through either core-level multiplet splittings or circular-polarized excitation of spin-orbit-split levels. The direct imaging of short-range atomic structure by both photoelectron holography and two distinct types of x-ray holography involving fluorescent emission is also discussed. Both photoelectron and x-ray holography have demonstrated the ability to directly determine at least approximate atomic structures in three dimensions. Photoelectron holography with spin resolution may make it possible also to study short-range magnetic order in a holographic fashion. Although much more recent in its first experimental demonstrations, x-ray fluorescence holography should permit deriving more accurate atomic images for a variety of materials, including both surface and bulk regions.     

碳基催化剂:为开发下一代纳米工程催化材料开辟新方法(英文)

This essay analyses some of the recent development in nanocarbons (carbon materials having a defined and controlled nano-scale dimension and functional properties which strongly depend on their nano-scale features and architecture), with reference to their use as advanced catalytic materials. It is remarked how their features open new possibilities for catalysis and that they represent a new class of catalytic materials. Although carbon is used from long time in catalysis as support and electrocatalytic applications, nanocarbons offer unconventional ways for their utilization and to address some of the new challenges deriving from moving to a more sustainable future. This essay comments how nanocarbons are a key element to develop next-generation catalytic materials, but remarking that this goal requires overcoming some of the actual limits in current research. Some aspects are discussed to give a glimpse on new directions and needs for RD to progress in this direction.     

Weighing synthetic polymers of ultra‐high molar mass and polymeric nanomaterials: What can we learn from charge detection mass spectrometry?

Advances in soft ionization techniques for mass spectrometry (MS) of polymeric materials make it possible to determine the masses of intact molecular ions exceeding megadaltons. Interfacing MS with separation and fragmentation methods has additionally led to impressive advances in the ability to structurally characterize polymers. Even if the gap to the megadalton range has been bridged by MS for polymers standards, the MS‐based analysis for more complex polymeric materials is still challenging. Charge detection mass spectrometry (CDMS) is a single‐molecule method where the mass and the charge of each ion are directly determined from individual measurements. The entire molecular mass distribution of a polymer sample can be thus accurately measured. Described in this perspective paper is how molecular weight distribution as well as charge distribution can provide new insights into the structural and compositional studies of synthetic polymers and polymeric nanomaterials in the megadalton to gigadalton range of molecular weight. The recent multidimensional CDMS studies involving couplings with separation and dissociation techniques will be presented. And, finally, an outlook for the future avenues of the CDMS technique in the field of synthetic polymers of ultra‐high molar mass and polymeric nanomaterials will be provided.     

Synthesis, characterization, and applications of dendrimer-encapsulated nanoparticles

In this article we describe the synthesis, characterization, and applications of dendrimer-encapsulated nanoparticles (DENs). These materials are synthesized by a template approach in which metal ions are extracted into the interior of dendrimers and then subsequently chemically reduced to yield nearly size-monodisperse particles having dimensions of less than 3 nm. Monometallic, bimetallic (including core/shell), and semiconductor nanoparticles have been prepared by this route. The dendrimer component of these composites serves not only as a template for preparing the nanoparticle replica but also to stabilize the nanoparticle, makes it possible to tune solubility, and provides a means for immobilization of the nanoparticle on solid supports. These materials have a number of potential applications, but the focus here is on catalysis. Homogeneous catalytic reactions, including hydrogenations, Heck coupling, and Suzuki reactions, in water, organic solvents, biphasic fluorous/organic solvents, and liquid and supercritical CO2 are discussed. In many cases it is easy to recycle catalytic DENs. DENs can also be immobilized on supports, such as silica and titania, and used for heterogeneous catalysis. Bimetallic DENs are shown to have particularly interesting catalytic properties. In addition to a discussion of current progress in this field, a number of intriguing questions related to the properties and potential applications of these materials are examined.     

HeI photoelectron and valence synchrotron photoionization studies of the thioester molecule CH3C(O)SCH3: evidence of vibronic structure

One of the simplest thioester molecules, S-methyl thioacetate, CH 3C(O)SCH 3, has been investigated by HeI photoelectron spectroscopy (PES) and valence photoionization studies using synchrotron radiation in the same energy range. In the second series of experiments, total ion yield (TIY), photoelectron photoion coincidence (PEPICO), and partial ion yield (PIY) spectra were recorded. It was found that the photodissociation behavior of CH 3C(O)SCH 3 can be divided into three well-defined energy regions. Vibronic structure was observed in the valence synchrotron photoionization process, being associated with wavenumbers of 912, 671, 1288, 1690, and 1409 cm (-1) for the bands at 12.82, 13.27, 15.66, 15.72, and 17.42 eV, respectively. Evaluation of the PE spectrum in concert with the synchrotron photoionization measurements and complemented by high-level ab initio calculations thus provides unusually detailed insights into the valence ionization processes of this molecule.     

分子氧氧化醇的研究进展

鉴于分子氧具有经济、环保、易得的优势,本文从均相催化、多相催化以及新材料的角度阐述了近年来液态醇选择氧化到醛酮的进展。着重介绍了过渡金属作为活性组分构成的催化体系,较详细的对新催化材料的研究做了一下归类,并对其在醇的氧化反应中的应用做了介绍,认为传统催化领域的研究仍然具有魅力,同时新材料的开发与运用在未来的具有诱人的前景。