The specific grain interior and grain boundary conductivities, obtained from impedance spectroscopy and the brick layer model, are reported for BaZr 0.9 Y 0.1 O 3 − δ as a function of p O 2 and temperature. p O 2-dependencies were indicative of dominating ionic and p-type electronic conduction for the grain interior under reducing and oxidizing conditions, respectively, while the grain boundaries showed an additional n-type electronic contribution under reducing conditions. Transmission electron microscopy revealed enrichment of Y in the grain boundary region. These findings indicate the existence of space-charge layers in the grain boundaries. A grain boundary core-space-charge layer model is therefore applied to interpret the data. Using a Mott-Schottky approximation, a Schottky barrier height of 0.5-0.6 V and an effective grain boundary width of 8-10 nm (= 2× space-charge layer thickness) is obtained at 250°C in wet oxygen. Finite-element modelling of the complex impedance over a grain boundary with a space-charge layer depletion of protons yields a distorted semicircle as observed in the impedance spectra.

A Cr/Al 2 O 3 alkane dehydrogenation catalyst exhibits a maximum in ethylene yield during an ethane dehydrogenation cycle. Isotopic labelling experiments with monolabelled 13 C-ethane and deuterium were used to elucidate whether the initial activity increase could be due to formation of an active, larger hydrocarbon intermediate on the surface. The results strongly indicate that this is not the case, and instead point to a traditional reaction cycle involving adsorption of ethane to form an ethyl species, followed by desorption of ethene and hydrogen. Transient kinetic data suggest that ethane adsorption is the rate-determining step of reaction.

Calcined hydrotalcite with or without added metal (Mg(Al)O, Pt/Mg(Al)O and Pt,Sn/Mg(Al)O) have been investigated with in situ X-ray Photoelectron Spectroscopy (XPS) during ethane dehydrogenation experiments. The temperature in the analysis chamber was 450ºC and the gas pressure was in the range 0.3 -1 mbar. Depth profiling of calcined hydrotalcite and platinum catalysts under reaction, oxidation and in hydrogenwater mixture was performed by varying the photon energy, covering an analysis depth of 10-21 Å. It was observed that the Mg/Al ratio in the Mg(Al)O crystallites does not vary significantly in the analysis depth range studied. This result indicates that Mg and Al are homogeneously distributed in the Mg(Al)O crystallites. Catalytic tests have shown that the initial activity of a Pt,Sn/Mg(Al)O catalyst increases during an activation period consisting of several cycles of reduction -dehydrogenation -oxidation. The Sn/Mg ratio in a Pt,Sn/Mg(Al)O catalyst was followed during several such cycles, and was found to increase during the activation period, probably due to a process where tin spreads over the carrier material and covers an increasing fraction of the Mg(Al)O surface. The results further indicate that spreading of tin occurs under reduction conditions. A PtSn 2 alloy was studied separately. The surface of the alloy was enriched in Sn during reduction and reaction conditions at 450°C. Binding energies were determined and indicated that Sn on the particle surface is predominantly in an oxidized state under reaction conditions, while Pt and a fraction of Sn is present as a reduced Pt-Sn alloy.

Silicon is often regarded as a likely candidate to replace graphite as the main active anode material in next-generation lithium ion batteries; however, a number of problems impacting its cycle stability have limited its commercial relevance. One approach to solving these issues involves the use of convertible silicon sub-oxides. In this work we have investigated amorphous silicon sub-nitride as an alternative convertible silicon compound by comparing the electrochemical performance of a-SiNx thin films with compositions ranging from pure Si to SiN0.89. We have found that increasing the nitrogen content gradually reduces the reversible capacity of the material, but also drastically increases its cycling stability, e.g. 40 nm a-SiN0.79 thin films exhibited a stable capacity of more than 1,500 mAh/g for 2,000 cycles. Consequently, by controlling the nitrogen content, this material has the exceptional ability to be tuned to satisfy a large range of different requirements for capacity and stability.

A new model for hydrogen-assisted fatigue crack growth (HAFCG) in BCC iron under a gaseous hydrogen environment has been established based on various methods of observation, i.e., electron backscatter diffraction (EBSD), electron channeling contrast imaging (ECCI) and transmission electron microscopy (TEM), to elucidate the precise mechanism of HAFCG. The FCG in gaseous hydrogen showed two distinguishing regimes corresponding to the 2 unaccelerated regime at a relatively low stress intensity factor range, ΔK, and the accelerated regime at a relatively high ΔK. The fracture surface in the unaccelerated regime was covered by ductile transgranular and intergranular features, while mainly quasi-cleavage features were observed in the accelerated regime. The EBSD and ECCI results demonstrated considerably lower amounts of plastic deformation, i.e., less plasticity, around the crack path in the accelerated regime. The TEM results confirmed that the dislocation structure immediately beneath the crack in the accelerated regime showed significantly lower development and that the fracture surface in the quasi-cleavage regions was parallel to the {100} plane. These observations suggest that the HAFCG in pure iron may be attributed to "less plasticity" rather than "localized plasticity" around the crack tip.

Herein, we report the discovery of a toroidal inorganic cluster of zirconium(IV) oxysulfate of unprecedented size with the formula Zr 70 (SO 4) 58 (O/OH) 146 •x(H 2 O) (Zr 70), which displays different packing of ring units and thus several polymorphic crystal structures. The ring measures over 3 nm across, has an inner cavity of 1 nm and displays a pseudo-10-fold rotational symmetry of Zr 6 octahedra bridged by an additional Zr in the outer rim of the ring. Depending on the cocrystallizing species, the rings form various crystalline phases in which the torus units are connected in extended chain and network structures. One phase, in which the ring units are arranged in layers and form one-dimensional channels, displays high permanent porosity (BET surface area: 241 m 2 g À1), and thus demonstrates a functional property for potential use in, for example, adsorption or heterogeneous catalysis.

Laboratory-based X-ray absorption spectroscopy (XAS) and especially X-ray absorption near-edge structure (XANES) offers new opportunities in catalyst characterization and presents not only an alternative, but also a complementary approach to precious beamtime at synchrotron facilities. We successfully designed a laboratory-based setup for performing operando, quasisimultaneous XANES analysis at multiple K-edges, more specifically, operando XANES of mono-, bi-, and trimetallic CO 2 hydrogenation catalysts containing Ni, Fe, and Cu. Detailed operando XANES studies of the multielement solid catalysts revealed metal-dependent differences in the reducibility and re-oxidation behavior and their influence on the catalytic performance in CO 2 hydrogenation. The applicability of operando laboratory-based XANES at multiple K-edges paves the way for advanced multielement catalyst characterization complementing detailed studies at synchrotron facilities.

We study the electronic structure of black phosphorus by combining state-of-the-art density functional theory, multiple scattering calculations and electron energy loss spectroscopy. The hybrid functionals HSE03 and PBE0 are tested to investigate whether they give an improved description compared to the more traditional PZ-LDA and PBE-GGA functionals. These calculations are compared with investigations of the conduction band using electron energy loss spectroscopy and calculations based on the real-space multiple scattering approach, and previous determinations of the bandgap. The hybrid functional HSE03 gives an improved correspondence with these experiments. Comparisons of the calculated valence band with previous XPS studies yield acceptable agreement for the traditional functionals, while the results from the hybrid functionals are less satisfactory, since the hybrid functionals overestimate the valence band width significantly.