This study targets one of the grand challenges of electrochemical hydrogen production: a durable and cost-effective oxygen-evolution catalyst. We present a thin-film composite electrode with a unique morphology and an ultralow loading of iridium that has extraordinary electrocatalytic properties. This is accomplished by the electrochemical growth of a defined, high-surface-area titanium oxide nanotubular film, followed by the nitridation and effective immobilization of iridium nanoparticles. The applicative relevance of this production process is justified by a high oxygen-evolution reaction (OER) activity and high stability. Enhanced OER performance is due to the strong metal–support interaction (SMSI). The high durability is achieved by self-passivation of the titanium oxynitride (TiON) surface layer with TiO2, which in addition also effectively embeds the Ir nanoparticles while still keeping them electrically wired. An additional contribution to the enhanced durability comes from the nitrogen atoms, which according to our density functional theory (DFT) calculations reduce the tendency of the Ir nanoparticles to grow. Materials are analyzed by advanced electrochemical characterization techniques. Namely, the entire process of the TiON–Ir electrode’s preparation and the electrochemical evaluation can be tracked with scanning electron microscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) at identical locations. In general, the experimental approach allows for the unique morphological, structural, and compositional insights into the preparation and electrocatalytic performance of thin films, making it useful also outside electrocatalysis applications.

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The influence of the flooding gas during ToF-SIMS depth profiling was studied to reduce the matrix effect and improve the quality of the depth profiles. The profiles were measured on three multilayered samples prepared by PVD. They were composed of metal, metal oxide, and alloy layers. Dual-beam depth profiling was performed with 1 keV Cs + and 1 keV O 2 + sputter beams and analyzed with a Bi + primary beam. The novelty of this work was the application of H 2 , C 2 H 2 , CO, and O 2 atmospheres during SIMS depth profiling. Negative cluster secondary ions, formed from sputtered metals/metal oxides and the flooding gases, were analyzed. A systematic comparison and evaluation of the ToF-SIMS depth profiles were performed regarding the matrix effect, ionization probability, chemical sensitivity, sputtering rate, and depth resolution. We found that depth profiling in the C 2 H 2 , CO, and O 2 atmospheres has some advantages over UHV depth profiling, but it still lacks some of the information needed for an unambiguous determination of multilayered structures. The ToF-SIMS depth profiles were significantly improved during H 2 flooding in terms of matrix-effect reduction. The structures of all the samples were clearly resolved while measuring the intensity of the M n H m – , M n O m – , M n O m H – , and M n – cluster secondary ions. A further decrease in the matrix effect was obtained by normalization of the measured signals. The use of H 2 is proposed for the depth profiling of metal/metal oxide multilayers and alloys.

We studied V-shaped twins of chrysoberyl (BeAl 2 O 4 ) from Rio das Pratinhas pegmatites near Arataca in the Bahia state of Brazil. The local structure of the twin boundaries was determined using powder X-ray diffraction analysis (XRD), transmission electron microscopy (TEM) methods, and density functional theory (DFT) calculations. To provide the most reliable model for DFT and HRTEM simulations the structure of chrysoberyl was first refined in the orthorhombic space group 62 (Pmnb) with unit-cell parameters: a = 5.4825(1) Å, b = 9.4163(2) Å, and c = 4.4308(1) Å, with 0.5 at% of Fe 3+ present on the Al(2) sites, suggesting an average composition of BeAl 1.99 Fe 0.01 O 4 . TEM study of V-shaped twins showed that the twin boundary lies in the (130) planes, and the angle measured between the crystal domains related by mirror twin operation is ∼59.5°. Rigid structural model of (130) twin boundary in chrysoberyl was refined by DFT calculations, using a pseudo-potential method. The twin boundaries show local enrichment with Ti. Bulk chrysoberyl contains numerous nanosized TiO 2 precipitates with a distorted rutile structure, following the orientation relationship of [001] Ch {120} Ch ||[010] R {103} R . The increase of Ti at the twin boundaries and the formation of rutile-type TiO 2 precipitates in bulk chrysoberyl suggest a transient Ti-exsolution that took place after the twin formation.