Reducing iridium loading in proton exchange membrane water electrolyzer anodes is essential to meet cost targets for large‐scale green hydrogen production. Here, we report a photodeposition‐based synthesis of TiO 2 @IrO 2 core‐shell catalysts with iridium contents as low as 10 wt%. The influence of annealing temperature, iridium content, and iridium loading on structural and electrochemical properties is systematically investigated. An annealing temperature of 450 °C provides the best compromise between activity, conductivity, and stability. Remarkably, even at 10 wt% Ir (≈4.5 vol% IrO 2 ), the core‐shell architecture maintains high electronic conductivity and mass activity. The low iridium content results in ~18 μm thick catalyst layers at a loading of 0.35 mg Ir cm −2 , corresponding to a high thickness factor of 52.0 ± 0.8 μm (mg Ir cm −2 ) −1 . Two‐dimensional, two‐phase performance modeling reveals that these thick catalyst layers improve electronic connectivity at low loadings, leading to higher catalyst utilization than a commercial reference. As a result, the core‐shell catalyst outperforms the reference in single‐cell measurements, achieving 1.77 V at 2 A cm −2 at a low loading of 0.31 mg Ir cm −2 . During 200 h durability testing, reversible degradation is observed, while irreversible losses remain on par with the reference and the core–shell structure is preserved.

Stainless steel is a promising material for bipolar plates (BPP) in proton exchange membrane water electrolysis (PEMWE) that could drastically reduce stack costs. However, dissolution of Fe from stainless steel BPP might trigger membrane degradation, which releases fluoride. Fluoride in turn could accelerate stainless steel corrosion. Therefore, the influence of fluoride contamination (namely 0, 1, 5, and 20 ppm in 0.5 mM H2SO4) on the dissolution stability of stainless steel (316L) is investigated utilizing a scanning flow cell coupled on-line to an inductively coupled plasma mass spectrometer (SFC-ICP-MS). Fluoride enhances the dissolution exponentially, resulting in enhanced dissolution efficiencies with increased fluoride concentration reaching ≈50% at 20 ppm. Complementary micro and nanostructure analysis (laser profilometry, scanning electron microscopy, and scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy) reveals pitting corrosion, whose severity and occurrence appear highly increased with higher fluoride concentration. The results suggest that fluoride impurities in combination with exposed stainless steel, e.g., due to coating imperfections, should be avoided in PEMWE application, as accumulation of impurities of both might lead to a self-accelerating degradation process.

Metallic nanosponges are well known to exhibit distinct mechanical properties that are considered to originate from the interwoven mechanics of the nanoscale ligaments as individual units and as a network. A comprehensive understanding of the physical mechanisms behind these properties spanning over several length scales is to date lacking. Here, by employing a correlative and scale-bridging workflow combining non-destructive 3D electron and X-ray tomography, in situ mechanics and experimentally-informed real-size modelling, we reveal the atomic origins of size dependent deformation mechanisms of nanoporous gold ranging from sub-ten to hundreds of nanometers. A realistic distribution of geometries and sizes of the ligaments appears to be crucial to accurately capture the mechanical response of nanoporous gold, including deformation gradients and plasticity. Our workflow demonstrates the potential for exploring the atomistic mechanisms of material plasticity with geometrical complexity. The mechanical properties of nanoporous gold are tied to their topology and surface morphology. Here, a correlative and scale-bridging approach, combining non-destructive 3D tomography, mechanical testing and experimentally-informed modelling, reveals the origins of the size dependent deformation mechanisms.

The influence of the polarity of ceramic substrates on the structural evolution of thin metal films during annealing at elevated temperatures is investigated, including the competing processes of solid state dewetting (SSD) and grain growth, as well as the atomic structure of the epitaxial interface. For this purpose, Au thin films on polar O-ZnO(0001) and Zn-ZnO(0001) surfaces are annealed at elevated temperatures and times. Whereas SSD dominates on the O-terminated surface, pronounced grain growth is observed on the Zn-terminated surface. The texture analysis revealed that up to 600 degrees C, both samples exhibit a fiber texture with slightly dominating Au (111)[110] || ZnO(0001)[1120] orientation relation (OR 2). At 800 degrees C, Au on Zn-ZnO exhibits a transformation to a mazed bicrystal structure with Au(111)[110] || ZnO(0001)[1010] orientation relation (OR 1). Comparison of various interface structures in density-functional theory (DFT) indicates that atomically sharp interfaces between the Au(111) films and the ideal bulk-truncated polar ZnO surfaces are energetically favored for both substrate polarities in excellent agreement with atomically resolved electron microscopy. Due to the larger period of the coincidence site lattice in OR 2, the corresponding interface can be described as semi-coherent with clearly separated misfit dislocations. In contrast, the much smaller period of the (approximate) coincidence site lattice in OR 1 leads to a largely incoherent interface with local reconstructions. However, in the experimental situation, even a small rotational deviation from the perfect OR 1 can introduce an interfacial screw dislocation network superimposed on the incoherent interface structure, effectively making the interface semi-coherent.

Electron tomography (ET) offers nanoscale 3D characterization of mesoporous materials but is often limited by their low scattering contrast. Here, we introduce a gallium (Ga) intrusion strategy for mesoporous silica that dramatically improves imaging contrast – a key benefit that enables more accurate 3D reconstructions. By infiltrating Ga through a modified mercury intrusion porosimetry process, the high-angle annular dark-field (HAADF) STEM signal is enhanced by 5 times, resulting in a 34 % improvement in reconstruction resolution and a 49 % enhancement in interface sharpness. In addition, the increased sample conductivity facilitates focused ion beam (FIB) milling by minimizing charging effects and reducing drift. This approach enables precise segmentation and quantitative analysis of pore connectivity and size distribution, thereby extending the applicability of ET to light-element non-conductive materials and advancing structure-property characterization of complex porous systems.

Stainless steel is a possible candidate for replacing titanium-based bipolar plates to reduce the cost of proton exchange membrane water electrolyzers. However, stainless steel is suspected to dissolve which could harm the system. Herein, we investigate the influence of applied potentials and temperatures on the dissolution stability of stainless steel (316L) in deionized (DI) water (pH approximate to 7) and highly diluted H2SO4 (pH approximate to 3) utilizing a scanning flow cell coupled on-line to an inductively coupled plasma mass spectrometer (SFC-ICP-MS). In H2SO4, the applied potentials critically influence the dissolution rates of 316L. Detrimental dissolution is observed at the open circuit potential, whereas dissolution is minimal in a potential window between 0.76 and 0.96 V. Temperature enhances the dissolution of 316L, especially due to a reduced stability of Cr. In DI water, the stability of 316L remains widely independent of potential and temperature, with dissolution rates remaining at an overall low level. Complementary scanning- and transmission electron microscopy reveal corrosion phenomena after electrochemical measurements in pH 3. Our results provide insights into factors influencing the stability of 316L and emphasize the importance of testing conditions that accurately mimic real-operations.

We present a comprehensive scale-bridging characterization approach for supported catalytically active liquid metal solutions (SCALMS) which combines lab-based X-ray microscopy, nano X-ray computed tomography (nano-CT), and correlative analytical transmission electron microscopy. SCALMS catalysts consist of low-melting alloy particles and have demonstrated high catalytic activity, selectivity, and long-term stability in propane dehydrogenation (PDH). We established an identical-location nano-CT workflow which allows us to reveal site-specific changes of Ga-Pt SCALMS before and after PDH. These observations are complemented by analytical transmission electron microscopy investigations providing information on the structure, chemical composition, and phase distribution of individual SCALMS particles. Key findings of this combined microscopic approach include (i) structural evolution of the SCALMS particles' GaOx shell, (ii) Pt segregation toward the oxide shell leading to the formation of Ga-Pt intermetallic phases, and (iii) cracking of the oxide shell accompanied by the release of liquid Ga-Pt toward the porous support.

Beyond their CO2 emittance when burned as fuels, hydrocarbons (HCs) serve as omnipresent raw materials and commodities. No matter if as liquid oil spills or the endless amounts of plastic roaming the oceans, HCs behave as persistent pollutants with water as main carrier to distribute. Even if their general chemical structure [-(CH2 )n -] is quite simple, the endless range of n leads to contaminations of different appearances and properties. A water remediation method based on superparamagnetic iron oxide nanoparticles (SPIONs) modified with self-assembled monolayers of alkyl phosphonic acid derivatives is presented. These molecules enable the SPIONs to non-covalently bind HCs, independently from the molecular weight, size and morphology. The attractive interaction is mainly based on hydrophobic and Coulomb interaction, which allows recycling of the SPIONs. The superparamagnetic core allows a simple magnetic collection and separation from the water phase which makes it a promising addition to wastewater treatment. Agglomerates of collected plastic "waste" even exhibit superior adsorption properties for crude oil, another hydrocarbon waste which gives these collected wastes a second life. This upcycling approach combined with presented recycling methods enables a complete recycling loop.

The self-assembly of shape-anisotropic nanocrystals intolarge-scalestructures is a versatile and scalable approach to creating multifunctionalmaterials. The tetrahedral geometry is ubiquitous in natural and manmadematerials, yet regular tetrahedra present a formidable challenge inunderstanding their self-assembly behavior as they do not tile space.Here, we report diverse supracrystals from gold nanotetrahedra includingthe quasicrystal (QC) and the dimer packing predicted more than adecade ago and hitherto unknown phases. We solve the complex three-dimensional(3D) structure of the QC by a combination of electron microscopy,tomography, and synchrotron X-ray scattering. Nanotetrahedron vertexsharpness, surface ligands, and assembly conditions work in concertto regulate supracrystal structure. We also discover that the surfacecurvature of supracrystals can induce structural changes of the QCtiling and eventually, for small supracrystals with high curvature,stabilize a hexagonal approximant. Our findings bridge the gap betweencomputational design and experimental realization of soft matter assembliesand demonstrate the importance of accurate control over nanocrystalattributes and the assembly conditions to realize increasingly complexnanopolyhedron supracrystals.

Epitaxial growth methods usually need dedicated equipment, high energy consumption to maintain pure vacuum conditions and evaporation of source materials, and elevated substrate temperatures. Solution epitaxial growth requires nothing of that but is rarely used because the achieved microstructures are of low quality, not homogeneous, and finally exhibit worse performances in devices. Here, an antisolvent-vapor-assisted-crystallization of metal-halide-perovskites as a method overcoming these disadvantages is demonstrated. The methylammonium lead tribromide exhibits van-der-Waals type of epitaxial growth on mica substrates, resulting in micro-crystallites whose shape can be controlled to be either triangular micro-prism or micro-cuboid. These micro-crystallites act as optical resonators supporting various optical modes and lasing is achieved under optical excitation with low thresholds and record high environmental stability. Selecting suitable resonators from a large variety of sizes allows control of mode spacing and finally mono-mode operation, considered to be an important feature of semiconductor laser devices. The achieved results are essentially competitive to those obtained by vapor phase epitaxial microstructures, highlighting that epitaxy of high-quality optoelectronic device structures is feasible by minimum technological efforts and energy consumption, which are of increasing importance considering issues such as global warming and the current energy crisis.

Journal Article Correlative Micro-Compression and 3D X-ray Nanotomography Study of the Fracture Behavior of TCP Phases in an Additively Manufactured Ni-Base Superalloy Get access Michael Sommerschuh, Michael Sommerschuh Institute of Micro- and Nanostructure Research (IMN) & Center for Nanoanalysis and Electron Microscopy (CENEM), Interdisciplinary Center for Nanostructured Films (IZNF), Department of Materials Science and Engineering, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Bavaria, Germany Corresponding authors: michi.sommerschuh@fau.de, erdmann.spiecker@fau.de Search for other works by this author on: Oxford Academic Google Scholar Janis Wirth, Janis Wirth Institute of Micro- and Nanostructure Research (IMN) & Center for Nanoanalysis and Electron Microscopy (CENEM), Interdisciplinary Center for Nanostructured Films (IZNF), Department of Materials Science and Engineering, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Bavaria, Germany Search for other works by this author on: Oxford Academic Google Scholar Benoit Merle, Benoit Merle Materials Science & Engineering - Institute I, Interdisciplinary Center for Nanostructured Films (IZNF), Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Erlangen, Bavaria, Germany Search for other works by this author on: Oxford Academic Google Scholar Julian Pistor, Julian Pistor Chair of Materials Science and Engineering for Metals (WTM), Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Erlangen, Bavaria, Germany Search for other works by this author on: Oxford Academic Google Scholar Silvan Englisch, Silvan Englisch Institute of Micro- and Nanostructure Research (IMN) & Center for Nanoanalysis and Electron Microscopy (CENEM), Interdisciplinary Center for Nanostructured Films (IZNF), Department of Materials Science and Engineering, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Bavaria, Germany Search for other works by this author on: Oxford Academic Google Scholar Thomas Przybilla, Thomas Przybilla Institute of Micro- and Nanostructure Research (IMN) & Center for Nanoanalysis and Electron Microscopy (CENEM), Interdisciplinary Center for Nanostructured Films (IZNF), Department of Materials Science and Engineering, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Bavaria, Germany Search for other works by this author on: Oxford Academic Google Scholar Carolin Körner, Carolin Körner Chair of Materials Science and Engineering for Metals (WTM), Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Erlangen, Bavaria, Germany Search for other works by this author on: Oxford Academic Google Scholar Mathias Göken, Mathias Göken Materials Science & Engineering - Institute I, Interdisciplinary Center for Nanostructured Films (IZNF), Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Erlangen, Bavaria, Germany Search for other works by this author on: Oxford Academic Google Scholar Benjamin Apeleo Zubiri, Benjamin Apeleo Zubiri Institute of Micro- and Nanostructure Research (IMN) & Center for Nanoanalysis and Electron Microscopy (CENEM), Interdisciplinary Center for Nanostructured Films (IZNF), Department of Materials Science and Engineering, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Bavaria, Germany Search for other works by this author on: Oxford Academic Google Scholar Erdmann Spiecker Erdmann Spiecker Institute of Micro- and Nanostructure Research (IMN) & Center for Nanoanalysis and Electron Microscopy (CENEM), Interdisciplinary Center for Nanostructured Films (IZNF), Department of Materials Science and Engineering, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Bavaria, Germany Corresponding authors: michi.sommerschuh@fau.de, erdmann.spiecker@fau.de Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 294–298, https://doi.org/10.1017/S1431927622001982 Published: 01 August 2022

Supraparticles are spherical colloidal crystals prepared by confined self-assembly processes. A particularly appealing property of these microscale structures is the structural color arising from interference of light with their building blocks. Here, we assemble supraparticles with high structural order that exhibit coloration from uniform, polyhedral metal-organic framework (MOF) particles. We analyse the structural coloration as a function of the size of these anisotropic building blocks and their internal structure. We attribute the angle-dependent coloration of the MOF supraparticles to the presence of ordered, onion-like layers at the outermost regions. Surprisingly, even though different shapes of the MOF particles have different propensities to form these onion layers, all supraparticle dispersions show well-visible macroscopic coloration, indicating that local ordering is sufficient to generate interference effects.

Hierarchical pore structures exhibit morphological features on several length scales, which govern important materials properties in catalysis, such as catalytic activity, diffusivity or selectivity. Correlative tomography offers unique opportunities for a comprehensive and scale‐bridging 3D characterization of such complex pore morphologies, which is crucial to further optimize materials design and synthesis routines. This study explores the capabilities of correlative 360° electron tomography (ET) and lab‐based nano X‐ray computed tomography (Nano‐CT) enabling 3D analyses of volumes of up to (60 µm)³ with down to nm resolution, as demonstrated for zeolite particles with embedded macropores. By first applying the two techniques to the same particle the higher resolution and fidelity of ET are used to improve the segmentation of pore space in the Nano‐CT reconstruction. Extended statistical relevance and access to interparticle pore space are obtained from reconstructions of larger particle agglomerates, using the large‐field‐of‐view mode of the Nano‐CT. The presented correlative approach enables real space analyses of important pore characteristics for comparison with complementary pore characterization techniques. Moreover, by investigating samples from different stages of the synthesis, 360°‐ET and Nano‐CT provide unique insights into the formation mechanism of porous materials, as demonstrated for the steam‐assisted crystallization of the macroporous zeolite particles.

Supersaturated Ni-Au solid solution particles were synthesized by rapid solid-state dewetting of bilayer thin films deposited onto c-plane sapphire single-crystals. Rapid thermal annealing above the miscibility gap of the Ni-Au system followed by quenching to room temperature resulted in textured and faceted submicron-sized particles as a function of alloying content in the range of 0-28 at% Au. Morphologically, the observed kinetic crystal shapes are confined by close-packed planes; in addition, high-index facets are identified as a function of alloying content by TEM cross-sectioning and equilibrium crystal shape simulations. All samples exhibit a distinct ( 111 ) out-of-plane as well as in-plane texture along densely packed directions. Lattice parameters extracted from independent orthogonal X-ray and electron diffraction techniques prove the formation of a solid solution without tetragonal distortion imposed by the sapphire substrate. At the particle-substrate interface of highly alloyed particles segregation of Au atoms as well as dislocations in stand-off position are found. These observations are in-line with a semi-coherent interface, where Au segregation is triggered by the reduction of the overall strain energy due to: (i) a lower shear modulus on the particle side of the interface, (ii) the shifting of misfit dislocations in stand-off position further away from the stiffer substrate and (iii) a reduction of intrinsic misfit dislocation strain energy on the tensile side. In addition, the mechanical properties of pure and alloyed particles were characterized by in situ compression experiments in the SEM. Typical force-displacement data of defect-free single-crystals were obtained, reaching the theoretical strength of Ni for particles smaller than 400 nm. Alloying changes the mechanical response from an intermittent and discrete plastic flow behavior into a homogeneous deformation regime at large compressive strain. (c) 2021 The Author(s). Published by Elsevier Ltd on behalf of Acta Materialia Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/ )

Hierarchical pore structures exhibit features on several length scales governing important materials properties. Correlative 360° electron tomography and lab-based Nano-CT allowing for scale-bridging 3D analyses of volumes of (60 μm)3 with nm-resolution were applied to macroporous zeolite particles. More details can be found in article number 2001154 by Benjamin Apeleo Zubiri, Erdmann Spiecker, and co-workers.

A scale-bridging study of the influence of TCP phases on the mechanical properties of an additive manufactured Ni-base superalloy combining microcompression testing, X-ray nanotomography and TEM - Volume 27 Issue S1

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Light-induced halide segregation limits the bandgap tunability of mixed-halide perovskites for tandem photovoltaics. Here we report that light-induced halide segregation is strain-activated in MAPb(I1−xBrx)3 with Br concentration below approximately 50%, while it is intrinsic for Br concentration over approximately 50%. Free-standing single crystals of CH3NH3Pb(I0.65Br0.35)3 (35%Br) do not show halide segregation until uniaxial pressure is applied. Besides, 35%Br single crystals grown on lattice-mismatched substrates (e.g. single-crystal CaF2) show inhomogeneous segregation due to heterogenous strain distribution. Through scanning probe microscopy, the above findings are successfully translated to polycrystalline thin films. For 35%Br thin films, halide segregation selectively occurs at grain boundaries due to localized strain at the boundaries; yet for 65%Br films, halide segregation occurs in the whole layer. We close by demonstrating that only the strain-activated halide segregation (35%Br/45%Br thin films) could be suppressed if the strain is properly released via additives (e.g. KI) or ideal substrates (e.g. SiO2). Mixed-halide perovskites are of interest for photovoltaic devices, but light-induced halide segregation obstructs bandgap tuning and is not fully understood. Here the authors study the effects of strain and iodide/bromide ratio on light-induced halide segregation in mixed-halide perovskites.

Material properties are often governed by morphologies on certain length scales which can be addressed by different 3D imaging techniques providing complementary advantages. Nanoparticulate agglomerates or macroporous particles in the lower μm-range are such examples and two appropriate methods for their 3D exploration are electron tomography (ET) and high-resolution X-ray tomography (Nano-CT). Whereas ET reaches spatial resolutions down to (1 nm)3 of volumes up to (3 μm)3, the resolution of laboratory Nano-CT can get down to (50 nm)3 with samples sizes of up to (64 μm)3. So, each technique has its benefits and there is always a balance between spatial resolution and sample size.

The structure of finite self-assembling systems depends sensitively on the number of constituent building blocks. Recently, it was demonstrated that hard sphere-like colloidal particles show a magic number effect when confined in spherical emulsion droplets. Geometric construction rules permit a few dozen magic numbers that correspond to a discrete series of completely filled concentric icosahedral shells. Here, we investigate the free energy landscape of these colloidal clusters as a function of the number of their constituent building blocks for system sizes up to several thousand particles. We find that minima in the free energy landscape, arising from the presence of filled, concentric shells, are significantly broadened. In contrast to their atomic analogues, colloidal clusters in spherical confinement can flexibly accommodate excess colloids by ordering icosahedrally in the cluster center while changing the structure near the cluster surface. In-between these magic number regions, the building blocks cannot arrange into filled shells. Instead, we observe that defects accumulate in a single wedge and therefore only affect a few tetrahedral grains of the cluster. We predict the existence of this wedge by simulation and confirm its presence in experiment using electron tomography. The introduction of the wedge minimizes the free energy penalty by confining defects to small regions within the cluster. In addition, the remaining ordered tetrahedral grains can relax internal strain by breaking icosahedral symmetry. Our findings demonstrate how multiple defect mechanisms collude to form the complex free energy landscape of hard sphere-like colloidal clusters.