Magnetic properties in perovskite titanates ATiO(3-& delta;) (A = Ca, Sr, Ba) were investigated before and after arc melting. Crystal structure analysis was conducted by powder synchrotron X-ray diffraction with Rietveld refinements. Quantitative chemical element analysis was carried out by X-ray photoelectron spectroscopy. Magnetic measurements were conducted by vibrating sample magnetometer and X-ray magnetic circular dichroism (XMCD). The magnetic properties are found to be affected by impurities of 3d elements such as Fe, Co, and Ni. Depending on the composition and crystal structure, the occupation of the magnetic ions in perovskite titanates is selectively varied, which is interpreted to be the origin of the different magnetic behaviors in arc-melted perovskite titanates ATiO(3-& delta;) (A = Ca, Sr, Ba). In addition, both formation of oxygen vacancies and the reduction of Ti4+ to Ti3+ during arc-melting also play a role as proven by XMCD. Nevertheless, preferential site occupation of magnetic impurities is dominant in the magnetic properties of arc-melted perovskite ATiO(3-& delta;) (A = Ca, Sr, Ba).

The application of ZnO materials as solid-state supports for molecular heterogeneous catalysis is contingent on the functionalization of the ZnO surface with stable self-assembled monolayers (SAMs) of catalyst linker molecules. Herein, experimental and theoretical methods are used to study SAMs of azide-terminated molecular catalyst linkers with two different anchor groups (silane and thiol) on poly and monocrystalline (0001, 101 over bar 0$10\bar{1}0$) ZnO surfaces. Angle-resolved and temperature-dependent X-ray photoelectron spectroscopy (XPS) is used to study SAM binding modes, thermal stabilities, and coverages. The binding strengths and atomistic ordering of the SAMs are determined via atom-probe tomography (APT). Density functional theory (DFT) and ab initio molecular dynamics (AIMD) calculations provide insights on the influence of the ZnO surface polarity on the interaction affinity and conformational behavior of the SAMs. The investigations show that SAMs based on 3-azidopropyltriethoxysilane possess a higher binding strength and thermal stability than the corresponding thiol. SAM surface coverage is strongly influenced by the surface polarity of ZnO, and the highest coverage is observed on the polycrystalline surface. To demonstrate the applicability of linker-modified polycrystalline ZnO as a catalyst support, a chiral Rh diene complex is immobilized on the azide-terminal of the SAM and its coverage is evaluated via XPS.

The prevalent global energy crisis calls for searching viable pathways for generating green hydrogen as an alternative energy resource. Dye-sensitized photocatalytic water splitting is a feasible solution to produce green hydrogen. However, identifying suitable catalysts has been one of the bottlenecks in driving dye-sensitized photocatalysis efficiently. In this work, we report a new class of electrocatalysts based on the layered Weyl semimetals MIrTe4 (M = Nb, Ta) for the Eosin Y (EY)-sensitized hydrogen evolution reaction (HER) under visible light illumination. NbIrTe4 and TaIrTe4 exhibit HER activities of ~ 18000 and ~ 14000 mol.g-1, respectively after 10h of irradiation with visible light. Time-dependent UV-Vis spectroscopy and high-pressure liquid chromatography coupled with mass spectroscopy analysis shed light on the reaction dynamics and enable deeper understanding of the observed trend in hydrogen evolution rates for MIrTe4 materials. MIrTe4 (M = Nb, Ta) semimetals outperform related catalysts including transition metal dichalcogenides and other Weyl semimetals in terms of HER activity using EY as photosensitizer and triethanolamine as the sacrificial agent. We hypothesize that the topology-related band inversion in MIrTe4 Weyl semimetals promotes a high density of metal d-states near the Fermi level, driving their high catalytic performance. This study introduces a new class of layered Weyl semimetals as efficient catalysts, and provides perspectives for designing topology-enhanced catalysts.

In the field of artificial photosynthesis with semiconductor light harvesters, the default cocatalyst morphologies are isotropic, 0D nanoparticles. Herein, the use of highly anisotropic 2D ruthenium oxide nanosheet (RONS) cocatalysts as an approach to enhance photocatalytic oxygen evolution (OER) rates on commercial WO3 nanoparticles (0D light harvester) is presented. At optimal cocatalyst loadings and identical photocatalysis conditions, WO3 impregnated with RONS (RONS/WO3) shows a fivefold increase in normalized photonic efficiency compared to when it is impregnated with conventional ruthenium oxide (rutile) nanoparticles (RONP/WO3). The superior RONS/WO3 performance is attributed to two special properties of the RONS: i) lower electrochemical water oxidation overpotential for RONS featuring highly active edge sites, and ii) decreased parasitic light absorption on RONS. Evidence is presented that OER photocatalytic performance can be doubled with control of RONS edges and it is shown that compared to WO3 impregnated with RONP, the advantageous optical properties and geometry of RONS decrease the fraction of light absorbed by the cocatalyst, thus reducing the parasitic light absorption on the RONS/WO3 composite. Therefore, the results presented in the current study are expected to promote engineering of cocatalyst morphology as a complementary concept to optimize light harvester-cocatalyst composites for enhanced photocatalytic efficiency.

High‐temperature sodium‐sulfur battery (HT Na–S) technology has attracted substantial interest in the stationary energy storage sector due to its low cost and high energy density. However, the currently used solid electrolyte (ß‐alumina) is expensive and can only be operated at high temperatures, which compromises safety. On the other hand, liquid electrolytes in room temperature sodium‐sulfur batteries (RT Na–S) are susceptible to dendrite formation and polysulfide shuttle. Consequently, an electrolyte with both solid (shuttle blocking) and liquid (ionic conductivity) properties to overcome the above‐mentioned issues is highly desired. Herein, a high‐performance quasi‐solid state crosslinked gel polymer electrolyte (GPE) prepared in situ using pentaerythritol triacrylate (PETA) exhibiting high ionic conductivity of 2.33 mS cm−1 at 25 °C is presented. The GPE‐based electrolyte shows high stability resulting in a high discharge capacity of >600 mAh gs−1 after 2500 cycles with an average Coulombic efficiency of 99.91%. Density functional theory calculations reveal a weak interaction between the Na+ ions and the oxygen molecules of the PETA moiety, which leads to a facile cation movement. The crosslinked polymer network is tightly connected to the cathode and can confine sulfides, thereby facilitating the conversion process.

Nonmagnetic Pd exhibits ferromagnetism in the nanosize regime. Various stabilization agents, including surfactants, metal oxide supports, polymers, and porous materials (e.g., metal-organic frameworks (MOFs)), have been employed to prevent the agglomeration of metal nanoparticles. However, magnetic properties are greatly affected by the structural and electronic changes imposed by these stabilizing agents. In particular, metal-MOF hybrids (NPs@MOFs) have reduced magnetic properties, as reported by several authors. Herein, we report the enhancement in magnetic properties resulting from the combination of magnetic Pd NPs with UiO-66(Hf), which exhibits ferromagnetism, and the corresponding modifications in the hybridized structures. These hybridized structures are found to be strongly ferromagnetic, showing high magnetization and coercivity. We observed that the magnetic property is enhanced by 2 to 3 times upon including the Pd NPs on the surface of a UiO-66(Hf) shell support. For a fundamental understanding, the magnetization (M-H data) of the hybridized structure is analyzed with a modified Langevin function.

Nanoporous gold (NPG) is a type of functional material that has been extensively investigated. Herein, a solid-phase reaction method was used to develop in situ NPG thin-film comprising Au nanobranch structures. The proposed method was found to be simple, fast and without complicated procedures. Electrochemical detection of nitrite was performed through cyclic voltammetry and linear sweep voltammetry. Test results demonstrated that the improved catalytic behaviour of the NPG for nitrite electrooxidation reaction is highly dependent on its unique morphology. These findings are expected to provide an effective and rational pathway for the design and optimization of nitrite electrochemical sensors. (C) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

Graphene of thickness a few atomic layers has been grown in Ni/a-C bilayers at temperatures as low as 300 degrees C by Ni-induced crystallization of the amorphous carbon (a-C) in high vacuum. The mechanism of such very low-temperature growth of graphene has been investigated by a combinatorial experimental approach including x-ray diffraction, scanning electron microscopy, Auger electron spectroscopy, x-ray photoelectron spectroscopy and transmission electron microscopy. The growth of this few atomic layer thickness graphene has been found to be mediated by a coupled grain-boundary (GB) diffusion/surface diffusion mechanism. GBs in the top Ni sublayer provide fast diffusion paths for C atoms through the Ni layer, as a result of which graphene layers form above the Ni. The revealed low-temperature growth mechanism of graphene induced by contact with a metal can be applicable in advancing research fields as metal-matrix graphene composites and advanced energy storage devices. (C) 2019 Elsevier Ltd. All rights reserved.

The rational design of highly active electrocatalysts for the ethanol electrooxidation reaction (EOR) is important for future commercial applications of efficient direct ethanol fuel cells. Herein, we describe application of a solid-phase reaction for the creation of a well-defined, high-efficiency, nanoporous gold (NPG) electrocatalyst for EOR. The evaluation of the feature size and physical properties of the NPG electrocatalysts was undertaken using field-emission scanning electron microscopy and high-resolution transmission electron microscopy. Additionally, the catalytic performance of the prepared NPG electrocatalysts was determined using cyclic voltammetry (CV) and chronoamperometry (CA), with results indicating that their enhanced electrocatalytic activities and long-term durability were highly dependent upon morphology. The created NPG exhibited a mass activity of 308 mA mg(Au)(-1) toward EOR in alkaline media, which is much higher than those of nanostructured Au catalysts. In particular, 800-cycle CV and 2000-s CA tests in alkaline solution consistently suggested excellent long-term stability and durability of the NPG. Our findings suggest the developed NPG as a promising electrocatalyst and an ideal substrate for multifunctional electrocatalysts for EOR.

The thermal oxidation of ZrAl2 in the temperature range of 550-750 degrees C in pure oxygen has been investigated by a combinational experimental approach using X-ray diffraction, scanning electron microscopy/energy dispersive spectrometer, Auger electron spectroscopy and cross-sectional transmission electron microscopy. The thermal oxidation leads to the growth of anomalously thick (up to 4.5 mu m) amorphous (Zr0.33Al0.67)O-1.66 surficial layers at temperatures as high as 750 degrees C. The oxidation kinetics obeys a parabolic law with an activation energy of 143 kJ/mol. The underlying mechanism for the formation of such micrometer-thick amorphous oxide surficial layers has been discussed on the basis of interface thermodynamics and the occurrence of high interface stability associated with a synchronous oxidation of Al and Zr elements. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

The effect of structural order in the parent alloy substrate on the oxidation kinetics and oxide phase evolution was investigated for the thermal oxidation of amorphous Cu33at.%Zr67at.% and crystalline CuZr2 alloys of identical compositions in the temperature range of 200-250 degrees C. It was found that, besides the strong preferential oxidation of Zr in both alloys, the lack of structural order in the amorphous Cu33at.%Zr67at.% alloy results in much slower oxidation kinetics, as well as in distinctly different microstructures of the oxide overgrowth and its Zr-depletion zone in the wake of the ZrO2 overlayer growth front. The experimental findings can be rationalized on the basis of the strikingly different atomic mobilities of Cu, Zr and dissolved O in the amorphous and crystalline alloys, which also results in different nucleation barriers for crystalline oxide nucleation. The thus obtained knowledge on the underlying oxidation mechanisms provides new and profound insights into the surface engineering of metallic alloys. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

To realize the commercial feasibility of nanoporous metal-based electrocatalysts in fuel cells, there is a need for a rapid and viable integrated process for fabricating membrane electrodes assemblies (MEAs). Herein, we report a type of electrocatalyst design for the glucose electro-oxidation reaction (GOR) based on a solid-phase reaction method. In the proposed design, structural defects and a nanoporous framework were integrated in a nanoporous gold (NPG) thin-film electrocatalyst to effectively boost the electrocatalytic behaviors for the GOR in an alkaline solution. The fabricated NPG thin-film catalyst was shown to exhibit a specific activity ca. 1.6 and 25.0 times higher than those of conventional NPG and polycrystalline Au and remarkably higher long-term cyclic stability. Hence, the proposed approach is a promising strategy for the integrated preparation of NPG-based MEAs, which are expected to ultimately promote the commercial applicability of fuel cells. (C) 2019 The Electrochemical Society.

High silicon content Al-Si composites with a composition of Al-40 wt% Si were fabricated via a highenergy ball milling method. The microstructure evolution of Al-40 wt% Si milled powders and sintered composites has been thoroughly studied by scanning electron microscopy, X-ray diffraction, energy-dispersive spectrometry and high-resolution transmission electron microscopy. The mechanism of ball milling Al-40 wt% Si powders has been disclosed in detail: fracture mechanism dominating in the early stages, followed by the agglomeration mechanism, finally reaching the balance between the fragments and the agglomerates. It has been found that the average particle sizes of mixed Al-Si powders can be refined to the nanoscale, and the crystallite sizes of Al and Si have been reduced to 10 nm and 62 nm upon milling for 2 h-50 h, respectively. The finally formed Al-Si interfaces after ball milling for 50 h are wellcohesive. A dense and homogenous Al-40 wt% Si composite have been achieved by solid-state sintering at 550 degrees C. The results thus provide an effective support for producing bulk nanostructured Al-Si composites. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

The difference in the microstructural and texture evolution of Al films grown on amorphous SiO2 (a-SiO2) and amorphous Ge (a-Ge) substrates have been investigated. Surprisingly, the a-Ge substrate was found to change the preferred orientation of Al grains from the conventional (1 1 1) to the unconventional (1 1 0). The effect of the high mobility of Ge atoms at the metal-semiconductor interface on the microstructural and texture evolution of the metal thin film was studied. The diffusion of the Al adatoms on the a-Ge substrate was suppressed owing to the segregation of Ge atoms at the film surface. The mobility of Al grain boundaries was also suppressed because of grain-boundary wetting by the Ge atoms. It is concluded that the a-Ge substrate could tailor the Al grain orientation from (1 1 1) to (1 1 0) owing to the change in the film-growth mode from three-dimensional to twodimensional nucleation. The concept of interaction-induced island-growth model, which is based on the Volmer-Weber growth model, is also discussed here. This work thus demonstrates how the atomic mobility at the interface of the metal thin film and the semiconductor substrate controls the film microstructure and texture during deposition.