Grundlagen der Natur

Perovskite oxynitride materials can act as effective photocatalysts for water splitting driven by visible light. A combined neutron and x-ray study now provides unique insight into the underlying processes at the solid–liquid interface and highlights how solar-to-hydrogen conversion can be improved.

We report on the development of a miniaturized device for operando X-ray diffraction during laser 3D printing. Its capabilities are demonstrated by ex situ printing of complex shapes and operando X-ray diffraction experiments using Ti-6Al-4V powder. 

In situ high-energy synchrotron X-ray diffraction experiments in combination with electron microscopy observations reveal the influence of the thermo-mechanical history and chemical composition on the ordering kinetics during isochronal heating of 18 karat Au alloys.

La_1–xSr_xCoO_3-δ perovskites are potential catalysts for the anodic reaction of alkaline water electrolyzers, i.e., the oxygen evolution reaction (OER). It is well-known that La_1–xSr_xCoO_3−δ perovskites can easily display strontium surface segregation, but how this influences the performance of La_1–xSr_xCoO_3−δ perovskites as anodic electrode in alkaline water electrolyzers, particularly in terms of OER activity, has not been unveiled yet. This study focuses on La_0.2Sr_0.8CoO_3−δ, which shows relatively high activity for the OER, and reveals the influence of the preparation temperature on the amount and morphology of segregated strontium-containing islands. Thin film samples were prepared at different temperatures by using pulsed laser deposition. Those samples were then characterized with synchrotron-based X-ray photoelectron spectroscopy “as prepared” and after being immersed in ultrapure water. We found that higher preparation temperatures enhance the segregation of strontium, which is then almost quantitatively removed by washing the samples with ultrapure water. After immersion in water, the samples expose a cobalt-rich surface. Investigating the OER activity as a function of the perovskite deposition temperature, it has been found that the higher the deposition temperature (i.e., the more extended the strontium segregation), the higher the OER activity. Such an effect has been linked to the higher amount of cobalt accessible after removing the strontium segregated islands.

The temperature-dependent segregation of strontium-containing species on LSCO electrodes has been studied by means of XPS, SEM and XRD. Such surface species dissolve almost quantitatively upon immersion in water, leaving cobalt oxide, the active site of the reaction, free. 

The Dikic group at the Goethe University in Frankfurt am Main, Germany has published the first results following the opening of the "PRIORITY COVID-19 Call” at SLS. 

The nature of high activity of Cu/ZnO catalyst in methanol synthesis remains the subject of intensive debate. Here, the authors are revisiting carbon dioxide hydrogenation mechanism using high-pressure operando techniques.

The need for sustainable, renewable and low-cost approaches is a driving force behind the development of solar-to-H₂ conversion technologies. This study aims to develop a new strategy using a visible-light photocatalyst coupled to a biocatalyst for H₂ production. Photocatalytic methyl viologen (MV²⁺) reduction activity was investigated to discover active oxynitrides. In comparative studies with LaTiO₂N, BaTaO₂N and Ta₃N₅, it was revealed that the suitable surface area, band gap and band edge potentials are some physical factors that are responsible for the photocatalytic behaviors of GaN:ZnO in MV²⁺ reduction. The activity is enhanced at higher concentrations and the alkaline pH of triethanolamine (TEOA). The expression of an active [FeFe]-hydrogenase from Escherichia coli (Hyd⁺E. coli) as a recombinant biocatalyst was confirmed by its MV˙⁺-dependent H₂ production activity. In the photobiocatalytic system of GaN:ZnO and Hyd⁺E. coli, the rate of H₂ production reached the maximum level in the presence of MV²⁺ as an electron mediator at neutral pH as a biocompatible condition. The present work reveals a novel hybrid system for H₂ production using visible-light active GaN:ZnO coupled to Hyd⁺E. coli, which shows the feasibility of being developed for photobiocatalytic H₂ evolution under solar light.

Ultra-fast operando X-ray diffraction experiments reveal the temporal evolution of low and high temperature phases and the formation of residual stresses during laser 3D printing of a Ti-6Al-4V alloy. The profound influence of the length of the laser-scanning vector  on the evolving microstructure is revealed and elucidated.  

In general, magnetism and superconductivity are antagonistic to each other. However, there are several families of superconductors in which superconductivity coexists with magnetism, and a few examples are known where the superconductivity itself induces spontaneous magnetism. The best known of these compounds are Sr₂RuO₄ and some non-centrosymmetric superconductors. Here, we report the finding of ...

The first demonstration of laser spectroscopy of a meson, achieved at PSI's πE5 beamline, opens up new avenues for precision studies of ‘exotic atoms’.