Search

Metallic nanoparticles are essential materials in various applications, such as nanomedicine, nanotechnology, and catalysis. While it is known that their catalytic performance is determined by their microstructure and thus by their preparation, the influence of an important but commonly used calcination treatment during nanoparticle preparation on their properties is often overlooked. Herein, structural and morphological changes during the calcination of Pd(NO3)2/ZnO are studied systematically by performing in situ heating experiments mimicking typical preparation conditions, by employing environmental scanning transmission electron microscopy. The effect of different calcination parameters on Pd(NO3)2/ZnO is explored and guidance to enhance control over the preparation of small supported nanoparticles is provided. It is shown that a calcination treatment of Pd(NO3)2/ZnO between 200 and 400 °C for 15–120 min is ideally suited to obtain particles smaller than 4 nm with a narrow size distribution. [ABSTRACT FROM AUTHOR]

The Ta/CoFeB/Pt/MgO/HfO2 system is investigated, whose magnetic anisotropy can be controlled through magneto‐ionic gating, using both ionic liquid and solid state gating, via a non‐oxidative mechanism combining reversible and irreversible gating effects. Analysis of X‐ray absorption spectroscopy at the Co and Fe edges reveals no indications of oxidation after gating, while a reversible change at the oxygen K edge suggests the involvement of oxygen species in the magneto‐ionic process. In addition, X‐ray diffraction measurements reveal that gating can irreversibly increase the crystalline volume of MgO, through an increase in the MgO/Mg(OH)2 ratio. This is in line with measurements in solid state devices showing that in a series of 150 gating cycles a reversible effect combines with a progressive increase in the strength of the perpendicular magnetic anisotropy contribution that saturates after extensive cycling. Consequently, the observed gate‐induced changes in magnetic anisotropy can be attributed to the combined effects of Mg(OH)2 dehydration into MgO (irreversible) and most likely a gentle reordering of oxygen species at the CoFeB interface (reversible) leading to a non‐oxidative magneto‐ionic mechanism. This study provides valuable insights into the underlying mechanisms governing the complex magneto‐ionic phenomena, including the coexistence of both reversible and irreversible effects, and a pathway to voltage‐control of crystalline order in spintronics materials. [ABSTRACT FROM AUTHOR]

The past decade has seen a growing trend toward utilizing (quasi) van der Waals growth for the heterogeneous integration of various materials for advanced electronics. In this work, pulsed‐laser deposition is used to grow HfO2 thin films on graphene/SiO2/Si. As graphene is easily damaged under standard oxide‐film deposition conditions, the process needs to be adjusted to minimize the oxidation and the collision‐induced damage. A systematic study is conducted in order to identify the crucial deposition parameters for diminishing the defect concentration in the graphene interlayer. For evaluating the quality of graphene, it is mainly relied on data obtained from Raman spectroscopy, using approaches beyond the Tuinstra‐Koenig relation. The results show that the defects are mainly a consequence of the high kinetic energy of the plasma‐plume particles. Using a relatively high Ar process pressure, a sufficiently low defect concentration is ensured, without compromising the quality of the HfO2 thin film. This enabled us to successfully prepare memristive devices with a filamentary type of switching, utilizing the graphene layer as a bottom electrode. The findings of this study can be easily transferred to other systems for the development of oxide electronic devices. [ABSTRACT FROM AUTHOR]

An interactive simulation of a transmission electron microscope (TEM) called TEMGYM Basic is developed here, which enables users to understand how to operate and control an electron beam without the need to access an instrument. TEMGYM Basic allows users to familiarize themselves with alignment procedures offline, reducing the time and money required to become a proficient TEM operator. In addition to teaching the basics of electron beam alignments, the software enables users to create bespoke microscope configurations and develop an understanding of how to operate the configurations without sitting at a microscope. TEMGYM Basic also creates static ray diagram figures for a given lens configuration. The available components include apertures, lenses, quadrupoles, deflectors and biprisms. The software design uses first‐order ray transfer matrices to calculate ray paths through each electron microscope component, and the program is developed entirely in Python to facilitate compatibility with machine‐learning packages for future exploration of automated control. [ABSTRACT FROM AUTHOR]

Conventional methods for fabricating multilayered ceramic membranes with ion conducting dense thin layers are often cumbersome, costly, and limited by poor adhesion between layers. Inspired by the architectural structure of the rooted grasses in soil, here, we report an interface‐reaction‐induced reassembly approach for the direct fabrication of Ce0.9Gd0.1O2−δ (CGO) thin layers rooted in the parent multilayered ceramic membranes by only one firing step. The CGO dense layers are very thin, and adhered strongly to the parent support layer, ensuring low ionic transport resistance and structural integrity of the multilayered membranes. When using as an oxygen permeable membrane for upgrading fossil‐fuel‐derived hydrogen, it shows very long durability in harsh conditions containing H2O, CH4, H2, CO2 and H2S. Furthermore, our approach is highly scalable and applicable to a wide variety of ion conducting thin layers, including Y0.08Zr0.92O2−δ, Ce0.9Sm0.1O2−δ and Ce0.9Pr0.1O2−δ. [ABSTRACT FROM AUTHOR]

CO2‐oxidative dehydrogenation of propane (CO2‐ODHP) provides a promising route for propylene production. Sufficient propane conversion and propylene selectivity remain a great challenge due to the difficulty in activating inert propane and CO2 simultaneously. Herein, a Sn doped CeO2 supported Pt (Pt/Sn‐CeO2) catalyst in CO2‐ODHP reaction is reported. Sn doping appears to kill two birds with one stone for propane and CO2 activation. On the one side, it increases the electron density of Pt species via PtSn alloy formation, promoting propane adsorption and C−H bond cleavage. On the other side, it enhances oxygen vacancy concentrations of CeO2 support, facilitating CO2 dissociation. A higher propylene selectivity (63.9 % vs 22.3 %) was obtained on 0.1 wt % Pt/1.0 wt % Sn‐CeO2 than that on 0.1 wt % Pt/CeO2 with a comparable propane conversion (15.1 % vs 14.3 %) at 550 °C after 240 min on stream. This work provides a reference for designing efficient catalysts. [ABSTRACT FROM AUTHOR]

Since the discovery of Rochelle salt a century ago, ferroelectric materials have been investigated extensively due to their robust responses to electric, mechanical, thermal, magnetic, and optical fields. These features give rise to a series of ferroelectric‐based modern device applications such as piezoelectric transducers, memories, infrared detectors, nonlinear optical devices, etc. On the way to broaden the material systems, for example, from three to two dimensions, new phenomena of topological polarity, improper ferroelectricity, magnetoelectric effects, and domain wall nanoelectronics bear the hope for next‐generation electronic devices. In the meantime, ferroelectric research has been aggressively extended to more diverse applications such as solar cells, water splitting, and CO2 reduction. In this review, the most recent research progress on newly emerging ferroelectric states and phenomena in insulators, ionic conductors, and metals are summarized, which have been used for energy storage, energy harvesting, and electrochemical energy conversion. Along with the intricate coupling between polarization, coordination, defect, and spin state, the exploration of transient ferroelectric behavior, ionic migration, polarization switching dynamics, and topological ferroelectricity, sets up the physical foundation ferroelectric energy research. Accordingly, the progress in understanding of ferroelectric physics is expected to provide insightful guidance on the design of advanced energy materials. [ABSTRACT FROM AUTHOR]

The shuttling behavior and sluggish conversion kinetics of intermediate lithium polysulfides (LiPS) represent the main obstacles to the practical application of lithium–sulfur batteries (LSBs). Herein, an innovative sulfur host is proposed, based on an iodine‐doped bismuth selenide (I‐Bi2Se3), able to solve these limitations by immobilizing the LiPS and catalytically activating the redox conversion at the cathode. The synthesis of I‐Bi2Se3 nanosheets is detailed here and their morphology, crystal structure, and composition are thoroughly. Density‐functional theory and experimental tools are used to demonstrate that I‐Bi2Se3 nanosheets are characterized by a proper composition and micro‐ and nano‐structure to facilitate Li+ diffusion and fast electron transportation, and to provide numerous surface sites with strong LiPS adsorbability and extraordinary catalytic activity. Overall, I‐Bi2Se3/S electrodes exhibit outstanding initial capacities up to 1500 mAh g−1 at 0.1 C and cycling stability over 1000 cycles, with an average capacity decay rate of only 0.012% per cycle at 1 C. Besides, at a sulfur loading of 5.2 mg cm−2, a high areal capacity of 5.70 mAh cm−2 at 0.1 C is obtained with an electrolyte/sulfur ratio of 12 µL mg−1. This work demonstrated that doping is an effective way to optimize the metal selenide catalysts in LSBs. [ABSTRACT FROM AUTHOR]

Atomically dispersed metals maximize the number of catalytic sites and enhance their activity. However, their challenging synthesis and characterization strongly complicates their optimization. Here, the aim is to demonstrate that tuning the electronic environment of atomically dispersed metal catalysts through the modification of their edge coordination is an effective strategy to maximize their performance. This article focuses on optimizing nickel‐based electrocatalysts toward alcohol electrooxidation in alkaline solution. A new organic framework with atomically dispersed nickel is first developed. The coordination environment of nickel within this framework is modified through the addition of carbonyl (CO) groups. The authors then demonstrate that such nickel‐based organic frameworks, combined with carbon nanotubes, exhibit outstanding catalytic activity and durability toward the oxidation of methanol (CH3OH), ethanol (CH3CH2OH), and benzyl alcohol (C6H5CH2OH); the smaller molecule exhibits higher catalytic performance. These outstanding electrocatalytic activities for alcohol electrooxidation are attributed to the presence of the carbonyl group in the ligand chemical environment, which enhances the adsorption for alcohol, as revealed by density functional theory calculations. The work not only introduces a new atomically dispersed Ni‐based catalyst, but also demonstrates a new strategy for designing and engineering high‐performance catalysts through the tuning of their chemical environment. [ABSTRACT FROM AUTHOR]

Imaging of biomolecules by ionizing radiation, such as electrons, causes radiation damage which introduces structural and compositional changes of the specimen. The total number of high‐energy electrons per surface area that can be used for imaging in cryogenic electron microscopy (cryo‐EM) is severely restricted due to radiation damage, resulting in low signal‐to‐noise ratios (SNR). High resolution details are dampened by the transfer function of the microscope and detector, and are the first to be lost as radiation damage alters the individual molecules which are presumed to be identical during averaging. As a consequence, radiation damage puts a limit on the particle size and sample heterogeneity with which electron microscopy (EM) can deal. Since a transmission EM (TEM) image is formed from the scattering process of the electron by the specimen interaction potential, radiation damage is inevitable. However, we can aim to maximize the information transfer for a given dose and increase the SNR by finding alternatives to the conventional phase‐contrast cryo‐EM techniques. Here some alternative transmission electron microscopy techniques are reviewed, including phase plate, multi‐pass transmission electron microscopy, off‐axis holography, ptychography and a quantum sorter. Their prospects for providing more or complementary structural information within the limited lifetime of the sample are discussed. [ABSTRACT FROM AUTHOR]

Spinel ferrites are an important class of materials, whose magnetic properties are of interest for industrial applications. The antiphase boundaries (APBs) that are commonly observed in spinel ferrite films can hinder their applications in spintronic devices and sensors, as a result of their influence on magnetic degradation and magnetoresistance of the materials. However, it is challenging to correlate magnetic properties with atomic structure in individual APBs due to the limited spatial resolution of most magnetic imaging techniques. Here, aberration‐corrected scanning transmission electron microscopy and electron energy‐loss magnetic chiral dichroism are used to measure the atomic structure and electron magnetic circular dichroism (EMCD) of a single APB in NiFe2O4 that takes the form of a rock salt structure interlayer and is associated with a crystal translation of (1/4)a[011]. First principles density functional theory calculations are used to confirm that this specific APB introduces antiferromagnetic coupling and a significant decrease in the magnitude of the magnetic moments, which is consistent with an observed decrease in EMCD signal at the APB. The results provide new insight into the physical origins of magnetic coupling at an individual defect on the atomic scale. [ABSTRACT FROM AUTHOR]

Phase transition is established to govern electrostatic energy storage for antiferroelectric (AFE)‐type dielectric capacitors. However, the source of inducing the phase transition and the pathway of storing the energy remains elusive so far given the ultrafast charging/discharging process under normal working conditions. Here, by slowing down the phase‐transition speed using electron‐beam irradiation as an external stimulus, the in situ dynamic energy‐storage process in AFE PbZrO3 is captured by using atomic‐resolution transmission electron microscopy. Specifically, it is found that oxygen‐lead‐vacancy‐induced defect core acts as a seed to initiate the antiferrodistortive‐to‐ferrodistortive transition in antiparallel‐Pb‐based structural frames. Associated with polarity evolution of the compressively strained defect core, the ferroelectric (FE)–ferrodistortive state expands bilaterally along the b‐axis direction and then develops into charged domain configurations during the energy‐storage process, which is further evidenced by observations at the ordinary FE states. With filling the gap of perception, the findings here provide a straightforward approach of unveiling the unit‐cell‐wise energy storage pathway in chemical defect‐engineered dielectric ceramics. [ABSTRACT FROM AUTHOR]

Lithium–sulfur batteries (LSBs) are considered to be one of the most promising next generation energy storage systems due to their high energy density and low material cost. However, there are still some challenges for the commercialization of LSBs, such as the sluggish redox reaction kinetics and the shuttle effect of lithium polysulfides (LiPS). Here a 2D layered organic material, C2N, loaded with atomically dispersed iron as an effective sulfur host in LSBs is reported. X‐ray absorption fine spectroscopy and density functional theory calculations prove the structure of the atomically dispersed Fe/C2N catalyst. As a result, Fe/C2N‐based cathodes demonstrate significantly improved rate performance and long‐term cycling stability. Fe/C2N‐based cathodes display initial capacities up to 1540 mAh g−1 at 0.1 C and 678.7 mAh g−1 at 5 C, while retaining 496.5 mAh g−1 after 2600 cycles at 3 C with a decay rate as low as 0.013% per cycle. Even at a high sulfur loading of 3 mg cm−2, they deliver remarkable specific capacity retention of 587 mAh g−1 after 500 cycles at 1 C. This work provides a rational structural design strategy for the development of high‐performance cathodes based on atomically dispersed catalysts for LSBs. [ABSTRACT FROM AUTHOR]

Oxygen octahedral tilting has been recognized to strongly interact with spin, charge, orbital, and lattice degrees of freedom in perovskite oxides. Here, we observe a strain‐driven stripe‐like morphology of two supertetragonal (monoclinic Cc and Cm) phases in the strained BiFeO3/LaAlO3 thin films. The two supertetragonal phases have a similar giant axial ratio but differences in oxygen pyramid tilting mode. Especially, the competition between polar instability and oxygen pyramid tilting is identified using atomically resolved scanning transmission electron microscopy, leading to the polarization rotation across the phase boundary. In addition, microtwins are observed in the Cc phase. Our findings provide new insights of the coupling between ferroelectric polarization and oxygen pyramid tilting in oxide thin films and will help to design novel phase morphology with desirable ferroelectric polarization and properties for new applications in perovskite oxides. [ABSTRACT FROM AUTHOR]

Fundamental understanding of anisotropic growth in oxide nanocrystals is crucial to establish new synthesis strategies and to tailor the nanoscale electronic, magnetic, optical, and electrocatalytic properties of these particles. While several growth investigations of metal alloy nanoparticles have been reported, mechanistic studies on the growth of ternary oxide materials are still missing. This work constitutes the first study on the evolution of anisotropic growth of manganese–cobalt oxide nanoparticles by monitoring the elemental distribution and morphology during the particle evolution via scanning transmission electron microscopy–X‐ray spectroscopy. A new growth mechanism based on a "solution‐solid‐solid" pathway for mixed manganese cobalt oxides is revealed. In this mechanism, the MnO seed formation occurs in the first step, followed by the surface Co enrichment, which catalyzes the growth along the <100> directions in all the subsequent growth stages, creating rod, cross‐, and T‐shaped mixed metal oxides, which preferentially expose {100} facets. It is shown that the interrelation of both Mn and Co ions initializes the anisotropic growth and presents the range of validity of the proposed mechanism as well as the shape‐determining effect based on the metal‐to‐metal ratio. [ABSTRACT FROM AUTHOR]

Porous particle superstructures of about 15 nm diameter, consisting of ultrasmall nanoparticles of iridium and iridium dioxide, are prepared through the reduction of sodium hexachloridoiridate(+IV) with sodium citrate/sodium borohydride in water. The water‐dispersible porous particles contain about 20 wt % poly(N‐vinylpyrrolidone) (PVP), which was added for colloidal stabilization. High‐resolution transmission electron microscopy confirms the presence of both iridium and iridium dioxide primary particles (1–2 nm) in each porous superstructure. The internal porosity (≈58 vol%) is demonstrated by electron tomography. In situ transmission electron microscopy up to 1000 °C under oxygen, nitrogen, argon/hydrogen (all at 1 bar), and vacuum shows that the porous particles undergo sintering and subsequent compaction upon heating, a process that starts at around 250 °C and is completed at around 800 °C. Finally, well‐crystalline iridium dioxide is obtained under all four environments. The catalytic activity of the as‐prepared porous superstructures in electrochemical water splitting (oxygen evolution reaction; OER) is reduced considerably upon heating owing to sintering of the pores and loss of internal surface area. [ABSTRACT FROM AUTHOR]

The defined assembly of nanoparticles (NPs) in polymer matrices is an important prerequisite for next‐generation functional materials. A promising approach to control NP positions in polymer matrices at the nanometer scale is the use of block copolymers. It allows the selective deposition of NPs in nanodomains, but the final defined and ordered positioning of the NPs within the domains has not been possible. This can now be achieved by coating NPs with block copolymers. The self‐assembly of block copolymer‐coated NPs directly leads to ordered microdomains containing ordered NP arrays with exactly one NP per unit cell. By variation of the grafting density, the inter‐nanoparticle distance can be controlled from direct NP surface contact to surface separations of several nanometers, determined by the thickness of the polymer shell. The method can be applied to a wide variety of block copolymers and NPs and is thus suitable for a broad range of applications. [ABSTRACT FROM AUTHOR]

Abstract: The development of alkaline exchange membrane fuel cell (AEMFC) is limited by the sluggish reaction at the anode. Even precious group metals (PGMs) are not effective hydrogen oxidation reaction (HOR) electrocatalysts in alkaline medium. In this manuscript, the original synthesis of effective HOR electrocatalysts for AEMFC is reported. Here, the limitations of using metal‐organic precursors are described and their replacement with organometallic precursors is proposed. It is shown that completely different nanostructures can be synthesized by the organometallic route, resulting in the formation of NiPd nano‐alloy or Ni@Pd core–shell nanoparticles, instead of Pd@Ni. The presence of both Pd and Ni on the catalyst surface has a drastic effect on its HOR activity, due to a bifunctional electrocatalytic mechanism with hydrogen binding on Pd and OH binding on Ni. The highest activity is measured for NiPd nano‐alloy, whose specific activity reaches 104   mA   mg Pd − 1 and 1.38     mA     cm Pd − 2 at 0.1 V versus reversible hydrogen electrode at 298 K. These are the highest values reported so far for an NiPd catalyst. By design, the synthetic approach is generic and can be applied to any pair of metals, either PGM or other transition metals, to synthesize alloyed or core–shell electrocatalysts. [ABSTRACT FROM AUTHOR]

Abstract: Knowledge of degradation pathways of catalyst/support ensembles aids the development of rational strategies to improve their stability. Here, this is exemplified using indium tin oxide (ITO)‐supported Platinum nanoparticles as electrocatalysts at fuel cell (FC) cathodes under degradation protocols to mimic operating conditions in two potential regimes. The evolution of crystal structure, composition, crystallite and particle size is tracked by in situ X‐ray techniques (small and wide angle scattering), metal dissolution by in situ scanning flow cell coupled with mass spectrometry (SFC ICP‐MS) and Pt surface morphology by advanced electron microscopy. In a regular FC operation regime, Pt poisoning rather than Pt particle growth, agglomeration, dissolution or detachment was found to be the likely origin of the observed degradation and ORR activity losses. In the start‐up regime degradation is actually suppressed and only minor losses in catalytic activity are observed. The presented data thus highlight the excellent nanoparticle stabilization and corrosion resistance of the ITO support, yet point to a degradation pathway involving Pt surface modifications by deposition of sub‐monolayers of support metal ions. The identified degradation pathway of the Pt/oxide catalyst/support couple contributes to our understanding of cathode electrocatalysts for polymer electrolyte fuel cells (PEFC). [ABSTRACT FROM AUTHOR]

The effects of thermal treatment on the microstructure of a Pt-Pd/Al2O3 oxidation catalyst and its activity for CO oxidation have been studied. The microstructural analysis was performed by using several high-resolution electron microscopy techniques such as STEM, FIB/SEM slice & view, SEM and EDX. A combination of these analytic techniques and advanced TEM specimen preparation allowed for three-dimensional probing at different length scales, avoiding the random character of conventionally crushed powder specimens owing to site specificity. A core-shell distribution of Pt-Pd nanoparticles within the alumina support particles, with enlarged nanoparticles (≈1.5 to 40 nm) present in the shell and small nanoparticles (<1.5 nm) in the core, was revealed in the untreated catalyst. A more uniform spatial distribution developed during thermal treatment at 700 °C or higher with larger nanoparticles forming in the core. Accompanying measurements of the catalytic activity for CO oxidation showed the detrimental effect of sintering of the small nanoparticles on the reaction rate and apparent activation energy of the reaction. [ABSTRACT FROM AUTHOR]

Direct ethanol fuel cells are attractive power sources based on a biorenewable, high energy-density fuel. Their efficiency is limited by the lack of active anode materials which catalyze the breaking of the C−C bond coupled to the 12-electron oxidation to CO2. We report shape-controlled PtNiRh octahedral ethanol oxidation electrocatalysts with excellent activity and previously unachieved low onset potentials as low as 0.1 V vs. RHE, while being highly selective to complete oxidation to CO2. Our comprehensive characterization and in situ electrochemical ATR studies suggest that the formation of a ternary surface site ensemble around the octahedral Pt3Ni1Rhx nanoparticles plays a crucial mechanistic role for this behavior. [ABSTRACT FROM AUTHOR]

Back Cover: Multilayered Ceramic Membrane with Ion Conducting Thin Layer Induced by Interface Reaction for Stable Hydrogen Production (Angew. Keywords: Hydrogen Production; Interface Reaction; Ion Conducting Thin Layer; Multilayered Ceramic Membrane; Oxygen Permeable Membrane EN Hydrogen Production Interface Reaction Ion Conducting Thin Layer Multilayered Ceramic Membrane Oxygen Permeable Membrane 1 1 1 01/31/23 20230201 NES 230201 B Multilayered ceramic membranes b with ion-conducting dense thin layers are essential platforms for solid-state electrochemical devices, gas separation membranes, and sensors. Hydrogen Production, Interface Reaction, Ion Conducting Thin Layer, Multilayered Ceramic Membrane, Oxygen Permeable Membrane. [Extracted from the article]

Keywords: Hydrogen Production; Interface Reaction; Ion Conducting Thin Layer; Multilayered Ceramic Membrane; Oxygen Permeable Membrane EN Hydrogen Production Interface Reaction Ion Conducting Thin Layer Multilayered Ceramic Membrane Oxygen Permeable Membrane 1 1 1 01/31/23 20230201 NES 230201 B Multilayered ceramic membranes b with ion-conducting dense thin layers are essential platforms for solid-state electrochemical devices, gas separation membranes, and sensors. Hydrogen Production, Interface Reaction, Ion Conducting Thin Layer, Multilayered Ceramic Membrane, Oxygen Permeable Membrane In their Research Article (e202210485), Heqing Jiang et al. develop a new interface-reaction-induced reassembly approach for the direct fabrication of zirconia- or ceria-based dense thin layers rooted in multilayered ceramic membranes that show robust and practical performance for upgrading fossil-fuel-derived hydrogen. [Extracted from the article]

The degradation of the functional properties of epitaxial oxide films and the performance of related devices have often been attributed to the presence of so-called interfacial 'dead layers'. Extensive efforts have been made to understand the origin of such dead layers and to avoid their formation. However, the results of these efforts have not been fully satisfactory, largely as a result of the complex origin of dead layers. Here, the dead layer is studied in a sample that contains hillocks of nominally La0.7Sr0.3MnO3 (LSMO) sandwiched between a ferroelectric PbTiO3 film and a Nb-doped SrTiO3 substrate using aberration-corrected (scanning) transmission electron microscopy, nanobeam electron magnetic circular dichroism spectroscopy, and related techniques. The results here reveal the presence of a 5 nm thick layer in the LSMO hillocks, close to the LSMO/Nb-SrTiO3 interface, which exhibits distinct structural and physical properties. The atomic, electronic, and magnetic structures and local chemistry of the interfacial layer are determined. It is found that octahedral rotations are suppressed in ultrathin regions at the edges of the hillocks, providing evidence for a strong effect of the adjacent Nb-SrTiO3 and PbTiO3. The formation of the dead layer is discussed in the light of lattice strain and valence changes of Mn ions. [ABSTRACT FROM AUTHOR]

Single-crystalline vanadium dioxide (VO2) nanostructures are of great interest because of their single-domain metal-to-insulator transition. In this paper, single-crystalline W-doped VO2 nanobeams are synthesized for optical and electrical applications. As a result of differences in the polarization of the beams along their transverse and longitudinal axes, dual-surface plasmon resonance peaks at 1344 and 619 nm are generated, resulting in an increase in the solar modulating abilities of the VO2 nanobeams. The conductivity of the single-crystalline W-doped VO2 nanobeams changes by three to four orders of magnitude at the transition temperature, which is of great importance for electrical applications. [ABSTRACT FROM AUTHOR]

The synthesis of nanotubes from layered compounds has generated substantial scientific interest. 'Misfit' layered compounds (MLCs) of the general formula [(MX)1+ x] m[TX2] n, where M can include Pb, Sb, rare earths; T=Cr, Nb, and X=S, Se can form layered structures, even though each sub-system alone is not necessarily a layered or a stable compound. A simple chemical method is used to synthesize these complex nanotubes from lanthanide-based misfit compounds. Quaternary nanotubular structures formed by partial substitution of the lanthanide atom in nanotubes by other elements are also confirmed. The driving force and mechanism of formation of these nanotubes is investigated by systematic temperature and time-dependent studies. A stress-inducement mechanism is proposed to explain the formation of the nanotubes. The resulting materials may find applications in fields that include thermoelectrics, light emitters, and catalysis and address fundamental physical issues in low dimensions. [ABSTRACT FROM AUTHOR]

This review highlights the importance of developing multi-scale characterisation techniques for analysing operating catalysts in their working environment. We emphasise that a hierarchy of in situ techniques that provides macro-, meso- and nano-scale information is required to elucidate and optimise catalyst performance fully. This combined methodology should ideally embrace spatially resolved and spatio-temporal monitoring of a) the structure, catalytic activity, temperature and heat/mass transfer pattern in axial and radial directions in real reactors, b) the structure and temperature/heat/mass transport gradients in shaped catalysts and catalyst grains and c) meso- and nano-scale information about particles and clusters, whose physical and electronic properties are linked directly to the micro-kinetic behaviour of the catalysts. Techniques such as X-ray diffraction (XRD), infrared (IR), Raman, X-ray photoelectron spectroscopy (XPS), UV/Vis, and X-ray absorption spectroscopy (XAS), which have mainly provided global atomic scale information, are being developed to provide the same information on a more local scale, often with sub-second time resolution. X-ray microscopy, both in the soft and more recently in the hard X-ray regime, allows two- and three-dimensional information to be collected down to 10 nm spatial resolution in a gas atmosphere or liquid, although this improvement is at the expense of temporal resolution. Electron microscopy, which provides excellent local atomic scale structural and spectroscopic information, is being developed towards tomographic imaging and realistic conditions, allowing gaps to be bridged in pressure, reaction conditions and length scales, up to the meso- and macro-scale. In addition, new techniques such as single molecule fluorescence spectroscopy and non-linear spectroscopic techniques are emerging. In this review, we discuss prospects for the development and combined application of both existing and new techniques for in situ catalyst characterisation. [ABSTRACT FROM AUTHOR]

A selection of recent results illustrating the application of off-axis electron holography to the study of magnetic microstructure in closely-spaced nanoparticles and nanowires is reviewed. Examples are taken from the characterization of FeNi nanoparticle chains, Co nanoparticle rings, two-dimensional arrays of naturally occurring magnetite crystals in minerals, and single crystalline Co nanowires. Approaches that can be used to separate the magnetic signal of interest from the mean inner potential contribution to the measured holographic phase shift are described, and the spatial and phase resolution that can be achieved are discussed. Microsc. Res. Tech. 64:390-402, 2004. © 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Photoelectrochemical Water Splitting: Boosting Photoelectrochemical Water Oxidation of Hematite in Acidic Electrolytes by Surface State Modification (Adv. In article number 1901836, Joan Ramon Morante, Jordi Arbiol and co-workers find that modifying the hematite/electrolyte interface with ultrathin Fe SB 2 sb TiO SB 5 sb and CoFe PBA improves the photoelectrochemical water oxidation of hematite photoanodes in acidic electrolytes. The modified hematite/electrolyte interface alters the surface states at hematite photoanodes, and thus improves the surface water oxidation kinetics. [Extracted from the article]

State‐of‐the‐art water‐oxidation catalysts (WOCs) in acidic electrolytes usually contain expensive noble metals such as ruthenium and iridium. However, they too expensive to be implemented broadly in semiconductor photoanodes for photoelectrochemical (PEC) water splitting devices. Here, an Earth‐abundant CoFe Prussian blue analogue (CoFe‐PBA) is incorporated with core–shell Fe2O3/Fe2TiO5 type II heterojunction nanowires as composite photoanodes for PEC water splitting. Those deliver a high photocurrent of 1.25 mA cm−2 at 1.23 V versus reversible reference electrode in acidic electrolytes (pH = 1). The enhancement arises from the synergic behavior between the successive decoration of the hematite surface with nanolayers of Fe2TiO5 and then, CoFe‐PBA. The underlying physical mechanism of performance enhancement through formation of the Fe2O3/Fe2TiO5/CoFe‐PBA heterostructure reveals that the surface states' electronic levels of hematite are modified such that an interfacial charge transfer becomes kinetically favorable. These findings open new pathways for the future design of cheap and efficient hematite‐based photoanodes in acidic electrolytes. [ABSTRACT FROM AUTHOR]

High energy density electrochemical systems such as metal batteries suffer from uncontrollable dendrite growth on cycling, which can severely compromise battery safety and longevity. This originates from the thermodynamic preference of metal nucleation on electrode surfaces, where obtaining the crucial information on metal deposits in terms of crystal orientation, plated volume, and growth rate is very challenging. In situ liquid phase transmission electron microscopy (LPTEM) is a promising technique to visualize and understand electrodeposition processes, however a detailed quantification of which presents significant difficulties. Here by performing Zn electroplating and analyzing the data via basic image processing, this work not only sheds new light on the dendrite growth mechanism but also demonstrates a workflow showcasing how dendritic deposition can be visualized with volumetric and growth rate information. These results along with additionally corroborated 4D STEM analysis take steps to access information on the crystallographic orientation of the grown Zn nucleates and toward live quantification of in situ electrodeposition processes. [ABSTRACT FROM AUTHOR]