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The structure of the first lithium containing bismuth ortho-thiophosphate was solved using a combination of powder X-ray, neutron, and electron diffraction. Li60–3xBi16+x(PS4)36 with x in the range of 4.2 to 6.7 possesses a complex monoclinic structure (space group C2/c, no. 15) and a large unit cell with lattice parameters a = 15.487Å, b = 10.323Å, c = 33.767Å, and = 85.394° for Li44.4Bi21.2(PS4)36. The disordered distribution of lithium ions within the interstices of the dense host-structure as well as the Li ion dynamics and diffusion pathways have been investigated by X-ray and neutron PDF analysis, solid-state NMR spectroscopy, PFG-NMR diffusion measurements, and BVS calculations. The total lithium ion conductivities range from 2.6 × 10−7 to 2.8 × 10−6 S cm−1 at 20 °C with activation energies between 0.29 and 0.32 eV, depending on the bismuth content. Despite the highly disordered nature of lithium ions in Li60–3xBi16+x(PS4)36, the underlying dense host-framework appears to limit the dimensionality of the lithium diffusion pathways and emphasizes once more the necessity of a close inspection of structure-property relationships in solid electrolytes.

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, A.G. and S.L. contributed equally to this work. Financial support is gratefully acknowledged from the Max Planck Society, the Cluster of Excellence “e-conversion” (EXC 2089/1–390776260), and the Center for Nanoscience. S.L. is thankful to the Science and Engineering Research Board (SERB), Government of India, for the award of a Ramanujan Fellowship (RJF/2021/000050). A.J.-S. gratefully acknowledges Spanish Ministry of Universities for funding through a Beatriz Galindo Research fellowship BG20/00015. The authors thank Prof. Gisela Schütz (Max Planck Institute for Intelligent Systems, MPI-IS, Stuttgart) for access to XPS analysis at their facilities. The authors are grateful to Dr. Gunther Richter for helpful discussion of XPS data and the MPI-IS for the XPS infrastructure support. The authors thank Andres RodríguezCamargo for FTIR and PXRD measurements and Marie-Luise Schreiber for extensive ICPOES elemental analysis. Open access funding enabled and organized by Projekt DEAL

Directed design of new photocatalysts remains a challenging task in materials chemistry. One approach in metal oxides is to engineer the bulk electronic structure to achieve enhanced visible-light ...

The development of all-solid-state sodium batteries for scalable energy storage solutions requires fast sodium conducting solid electrolytes. To fast-track their discovery, candidate materials need to be identified that are synthesized from abundant resources via cheap and green synthesis routes. Their ion conducting mechanism has to be understood and adapted to meet the stringent requirements for long-term operation in all-solid-state batteries. Here, structure and properties of the sodium hexathiohypodiphosphate Na4P2S6 obtained by two different synthesis methods are compared: a solid-state reaction and a precipitation route from aqueous solution. Combined investigations using powder X-ray diffraction (PXRD), precession electron diffraction (PED), differential scanning calorimetry (DSC), solid-state nuclear magnetic resonance spectroscopy (ssNMR), and Raman spectroscopy reveal that the solid-state synthesized material is characterized by a Na+ and vacancy disorder-driven enantiotropic phase transition at 160 °C (α- to β-Na4P2S6), which is accompanied by a symmetry change of the P2S64− anion. Precipitated Na4P2S6 already crystallizes in a β-like polymorph at room temperature, likely assisted by inter- and intralayer defects. Bond-valence and nudged elastic band (NEB) calculations were employed to identify a low energy, 2D conduction network in β-Na4P2S6, suggesting facile 2D long-range Na+ diffusion. Electrochemical impedance spectroscopy reveals a higher ionic conductivity at room temperature in precipitated β-like Na4P2S6 (2 × 10−6 S cm−1) compared to the solid-state α polymorph (7 × 10−7 S cm−1). The activation energy is around 0.4 eV for both materials. The findings highlight that even subtle structural changes can significantly impact the sodium-ion diffusion in solid electrolytes and at the same time reveal an intricate interplay between phase formation and synthetic control.

In this study, a strategy to prepare CuO/Cu2O/Cu microwires that are fully covered by a nanowire (NW) network using a simple thermal-oxidation process is developed. The CuO/Cu2O/Cu microwires are fixed on Au/Cr pads with Cu microparticles. After thermal annealing at 425 °C, these CuO/Cu2O/Cu microwires are used as room-temperature 2-propanol sensors. These sensors show different dominating gas responses with operating temperatures, e.g., higher sensitivity to ethanol at 175 °C, higher sensitivity to 2-propanol at room temperature and 225 °C, and higher sensitivity to hydrogen gas at ∼300 °C. In this context, we propose the sensing mechanism of this three-in-one sensor based on CuO/Cu2O/Cu. X-ray diffraction (XRD) studies reveal that the annealing time during oxidation affects the chemical appearance of the sensor, while the intensity of reflections proves that for samples oxidized at 425 °C for 1 h the dominating phase is Cu2O, whereas upon further increasing the annealing duration up to 5 h, the CuO phase becomes dominant. The crystal structures of the Cu2O-shell/Cu-core and the CuO NW networks on the surface were confirmed with a transmission electron microscope (TEM), high-resolution TEM (HRTEM), and selected area electron diffraction (SAED), where (HR)TEM micrographs reveal the monoclinic CuO phase. Density functional theory (DFT) calculations bring valuable inputs to the interactions of the different gas molecules with the most stable top surface of CuO, revealing strong binding, electronic band-gap changes, and charge transfer due to the gas molecule interactions with the top surface. This research shows the importance of the nonplanar CuO/Cu2O layered heterostructure as a bright nanomaterial for the detection of various gases, controlled by the working temperature, and the insight presented here will be of significant value in the fabrication of new p-type sensing devices through simple nanotechnology.

Carbon nitrides are among the most studied materials for photocatalysis, however, limitations arise from inefficient charge separation and transport within the material. Here, this aspect is addressed in the 2D carbon nitride poly(heptazine imide) (PHI) by investigating the influence of various counterions, such as M = Li+, Na+, K+, Cs+, Ba2+, NH4+ and tetramethyl ammonium, on the material’s conductivity and photocatalytic activity. These ions in the PHI pores affect the stacking of the 2D layers, which further influences the predominantly ionic conductivity in M-PHI. Na-containing PHI outperforms the other M-PHI in various relative humidity (RH) environments (0-42 %RH) in terms of conductivity, likely due to pore channel geometry and size of the (hydrated) ion. With increasing RH, the ionic conductivity increases by 4-5 orders of magnitude (for Na-PHI up to 10-5 S cm-1 at 42 %RH). At the same time, the highest photocatalytic hydrogen evolution rate is observed for Na-PHI, which is mirrored by increased photo-generated charge carrier lifetimes, pointing to efficient charge carrier stabilization by mobile ions. These results indicate that ionic conductivity is an important parameter that can influence the photocatalytic activity. Besides, RH-dependent ionic conductivity is of high interest for separators, membranes, or sensors.

The in-depth understanding of the reported photoelectrochemical properties of the layered carbon nitride, poly(triazine imide)/LiCl (PTI/LiCl), has been limited by the apparent disorder of the Li/H atoms within its framework. To understand and resolve the current structural ambiguities, an optimized one-step flux synthesis (470 oC, 36 h, LiCl/KCl flux) was used to prepare PTI/LiCl and deuterated-PTI/LiCl in high purity. Its structure was characterized by a combination of neutron/X-ray diffraction and transmission electron microscopy. The range of possible Li/H atomic configurations were enumerated for the first time and, combined with total energy calculations, reveals a more complex energetic landscape than previously considered. Experimental data were fitted against all possible structural models, exhibiting the most consistency with a new orthorhombic model (Sp. Grp. Ama2) that also has the lowest total energy. In addition, a new Cu(I)-containing PTI (PTI/CuCl) was prepared with the more strongly scattering Cu(I) cations in place of Li, and which also most closely matched with the partially-disorded structure in Cmc21. Thus, a complex configurational landscape of PTI is revealed to consist of a number of ordered crystalline structures that are new potential synthetic targets, such as with the use of metal-exchange reactions.

Summary Quantitative comparison of photocatalytic performances across different photocatalysis setups is technically challenging. Here, we combine the concepts of relative and optimal photonic efficiencies to normalize activities with an internal benchmark material, RuO2 photodeposited on a P25-TiO2 photocatalyst, which was optimized for reproducibility of the oxygen evolution reaction (OER). Additionally, a general set of good practices was identified to ensure reliable quantification of photocatalytic OER, including photoreactor design, photocatalyst dispersion, and control of parasitic reactions caused by the sacrificial electron acceptor. Moreover, a method combining optical modeling and measurements was proposed to quantify the benchmark absorbed and scattered light (7.6% and 81.2%, respectively, of λ = 300–500 nm incident photons), rather than just incident light (≈AM 1.5G), to estimate its internal quantum efficiency (16%). We advocate the adoption of the instrumental and theoretical framework provided here to facilitate material standardization and comparison in the field of artificial photosynthesis., Graphical Abstract, Highlights • A highly reproducible photocatalyst, RuO2/TiO2, has been developed as a benchmark system for the oxygen evolution reaction • A concept of relative photonic efficiency using this benchmark is introduced • A method to estimate internal quantum efficiency is proposed • Best practices to ensure the reliable quantification of photocatalytic O2 evolution data, Progress and Potential The continuous increase of atmospheric CO2 levels at alarming rates has put photocatalytic water splitting in the spotlight as a source of “green” energy . However, quantitative comparison of photocatalytic activities across different labs remains challenging, since it involves multiple factors including light scattering and reactor design. Here, we propose two methods to compare photocatalytic performance for the oxygen evolution reaction (OER) across different setups, and put forward a set of good practices to ensure its quantification: first, a benchmark OER photocatalyst (RuO2/TiO2) for the reliable determination of relative photonic efficiencies, and second, a procedure for estimating internal quantum efficiency by means of optical modeling and light-scattering measurements. These methods will open up new avenues for reliable comparison of photocatalytic performance across different laboratories and give a better overview and insight to the field., We present an approach to compare intrinsic material efficiencies in the field of artificial photosynthesis by means of highly reproducible photodeposited RuO2 on commercial TiO2 (P25) as a benchmark system. This is a challenging undertaking for which we present conceptual discussion and offer practical solutions. Here, we put forward two complementary methods (relative photonic efficiency and internal quantum efficiency) to achieve standardization of photocatalytic oxygen evolution reaction rates measured in different experimental setups and present a set of best experimental practices for reliable quantification.

The rational design of catalysts is crucial to make power-to-X technologies viable. Here the authors introduce the delafossite PdCoO2 as a highly active hydrogen evolution reaction catalyst due to the growth of a tensile-strained Pd-rich capping layer under reductive conditions. Image credit: Christop Hohmann., The rational design of hydrogen evolution reaction electrocatalysts that can compete with platinum is an outstanding challenge in the process of designing viable power-to-gas technologies. Here, we introduce delafossites as a family of hydrogen evolution reaction electrocatalysts in acidic media. We show that, in PdCoO2, the inherently strained Pd metal sublattice acts as a pseudomorphic template for the growth of a tensile-strained Pd-rich capping layer under reductive conditions. The surface modification ranges up to 400 nm and continuously improves the electrocatalytic activity by simultaneously increasing the exchange current density and by reducing the Tafel slope down to 38 mV dec(-1), leading to overpotentials eta(10) < 15 mV. The improved activity is attributed to the operando stabilization of a beta-PdHx phase with enhanced surface catalytic properties with respect to pure or nanostructured palladium. These findings illustrate how operando-induced electrodissolution can be used as a top-down design concept through the strain-stabilized formation of catalytically active phases.

Solving the structure of carbon nitrides has been a long-standing challenge due to the low crystallinity and complex structures observed within this class of earth-abundant photocatalysts. Herein, we report on two-dimensional layered potassium poly(heptazine imide) (K-PHI) and its proton-exchanged counterpart (H-PHI), obtained by ionothermal synthesis using a molecular precursor route. We present a comprehensive analysis of the in-plane and three-dimensional structure of PHI. Transmission electron microscopy and solid-state NMR spectroscopy, supported by quantum-chemical calculations, suggest a planar, imide-bridged heptazine backbone with trigonal symmetry in both K-PHI and H-PHI, whereas pair distribution function analyses and X-ray powder diffraction using recursive-like simulations of planar defects point to a structure-directing function of the pore content. While the out-of-plane structure of K-PHI exhibits a unidirectional layer offset, mediated by hydrated potassium ions, H-PHI is characterized by a high degree of stacking faults due to the weaker structure directing influence of pore water. Structure-property relationships in PHI reveal that a loss of in-plane coherence, materializing in smaller lateral platelet dimensions and increased terminal cyanamide groups, correlates with improved photocatalytic performance. Size-optimized H-PHI is highly active toward photocatalytic hydrogen evolution, with a rate of 3363 mu mol/gh H-2 placing it on par with the most active carbon nitrides. K- and H-PHI adopt a uniquely long-lived photoreduced polaronic state in which light-induced electrons are stored for more than 6 h in the dark and released upon addition of a Pt cocatalyst. This work highlights the importance of structure- property relationships in carbon nitrides for the rational design of highly active hydrogen evolution photocatalysts.

A cross-section analysis is presented of defects in ZnO nanospikes, investigated by means of transmission electron microscopy and defect simulation., The examination of anisotropic nanostructures, such as wires, platelets or spikes, inside a transmission electron microscope is normally performed only in plan view. However, intrinsic defects such as growth twin interfaces could occasionally be concealed from direct observation for geometric reasons, leading to superposition. This article presents the shadow-focused ion-beam technique to prepare multiple electron-beam-transparent cross-section specimens of ZnO nanospikes, via a procedure which could be readily extended to other anisotropic structures. In contrast with plan-view data of the same nanospikes, here the viewing direction allows the examination of defects without superposition. By this method, the coexistence of two twin configurations inside the wurtzite-type structure is observed, namely and , which were not identified during the plan-view observations owing to superposition of the domains. The defect arrangement could be the result of coalescence twinning of crystalline nuclei formed on the partially molten Zn substrate during the flame-transport synthesis. Three-dimensional defect models of the twin interface structures have been derived and are correlated with the plan-view investigations by simulation.

A big challenge for nonlinear optical (NLO) materials is the application in high power lasers, which needs the simultaneous occurrence of large second harmonic generation (SHG) and high laser induced damage threshold (LIDT). Herein we report the preparation of a new Ga2 Se3 phase, which shows the SHG intensities of around 2.3 times and the LIDT of around 16.7 times those of AgGaS2 (AGS), respectively. In addition, its IR transparent window ca. 0.59-25 μm is also significantly wider than that of AGS (ca. 0.48-≈11.4 μm). The occurrence of the strong SHG responses and good phase-matching indicate that the structure of the new Ga2 Se3 phase can only be non-centrosymmetric and have a lower symmetry than the cubic γ-phase. The observed excellent SHG and phase-matching properties are consistent with our diffraction experiments and can be well explained by using the orthorhombic models obtained through our high throughput simulations.

The carbon nitride poly(heptazine imide), PHI, has recently emerged as a powerful 2D carbon nitride photocatalyst with intriguing charge storing ability. Yet, insights into how morphology, particle size and defects influence its photophysical properties are virtually absent. Here, ultrasonication is used to systematically tune the particle size as well as concentration of surface functional groups and study their impact. Enhanced photocatalytic activity correlates with an optimal amount of those defects that create shallow trap states in the optical band gap, promoting charge percolation, as evidenced by time-resolved photoluminescence spectroscopy, charge transport studies, and quantum-chemical calculations. Excessive amounts of terminal defects can act as recombination centers and hence, decrease the photocatalytic activity for hydrogen evolution. Re-agglomeration of small particles can, however, partially restore the photocatalytic activity. The type and amount of trap states at the surface can also influence the deposition of the co-catalyst Pt, which is used in hydrogen evolution experiments. Optimized conditions entail improved Pt distribution, as well as an enhanced wettability and colloidal stability. A description of the interplay between these effects is provided to obtain a holistic picture of the size–property–activity relationship in nanoparticulate PHI-type carbon nitrides that can likely be generalized to related photocatalytic systems.

Covalent organic frameworks have emerged as a powerful synthetic platform for installing and interconverting dedicated molecular functions on a crystalline polymeric backbone with atomic precision. Here, we present a novel strategy to directly access amine-linked covalent organic frameworks, which serve as a scaffold enabling pore-wall modification and linkage-interconversion by new synthetic methods based on Leuckart-Wallach reduction with formic acid and ammonium formate. Frameworks connected entirely by secondary amine linkages, mixed amine/imine bonds, and partially formylated amine linkages are obtained in a single step from imine-linked frameworks, or directly from corresponding linkers in a one-pot crystallisation-reduction approach. The new, 2D amine-linked covalent organic frameworks, rPI-3-COF, rTTI-COF, and rPy1P-COF, are obtained with high crystallinity and large surface areas. Secondary amines, installed as reactive-sites on the pore wall, enable further post-synthetic functionalisation to access tailored covalent organic frameworks, with increased hydrolytic stability, as potential heterogeneous catalysts.

In this study, a strategy to prepare CuO/Cu

3D networks of Al-doped ZnO tetrapods decorated with ZnAl2O4particles synthesised by the flame transport method were investigated in detail using optical techniques combined with morphological/structural characterisation. Low temperature photoluminescence (PL) measurements revealed spectra dominated by near band edge (NBE) recombination in the UV region, together with broad visible bands whose peak positions shift depending on the ZnO?:?Al mixing ratios. A close inspection of the NBE region evidences the effective doping of the ZnO structures with Al, as corroborated by the broadening and shift of its peak position towards the expected energy associated with the exciton bound to Al. Both temperature and excitation density-dependent PL results pointed to an overlap of multiple optical centres contributing to the broad visible band, with the peak position dependent on the Al content. While in the reference sample the wavelength of the green band remained unchanged with temperature, in the case of the composites, the deep level emission showed a blue shift with increasing temperature, likely due to distinct thermal quenching of the overlapping emitting centres. This assumption was further validated by the time-resolved PL data, which clearly exposed the presence of more than one optical centre in this spectral region. PL excitation analysis demonstrated that the luminescence features of the Al-doped ZnO/ZnAl2O4composites revealed noticeable changes not only in deep level recombination, but also in the material's bandgap when compared with the ZnO reference sample. At room temperature, the ZnO reference sample exhibited free exciton resonance at ~3.29 eV, whereas the peak position for the Al-doped ZnO/ZnAl2O4samples occurred at ~3.38 eV due to the Burstein-Moss shift, commonly observed in heavily doped semiconductors. Considering the energy shift observed and assuming a parabolic conduction band, a carrier concentration of ~1.82 ×1019cm-3was estimated for the Al-doped ZnO/ZnAl2O4samples.

Powder samples of Ag3LiIr2O6 and Ag3LiRu2O6 were synthesized from alpha-Li2IrO3 and Li2RuO3 respectively by ion exchange in an AgNO3 melt. The crystal structures of the title compounds were solved from high resolution laboratory X-ray powder diffraction (XRPD) patterns and from pair distribution function (PDF) analysis using synchrotron X-ray powder diffraction data. In both crystal structures edge sharing LiO6/3- and (Ir/Ru)O-6/3-octahedra form honeycomb like layers that are stacked in a staggered fashion. Silver cations, situated in-between the layers mediate the interlayer interactions by linear O-Ag-O bonds. Anisotropic peak broadening in the XRPD patterns and diffuse scattering occurring as streaks in the precession electron diffraction (PED) patterns indicate the presence of stacking faults, which could be also visualized by high resolution transmission electron microscopy (HRTEM). Possible alternative stacking sequences were derived from the ideal crystal and incorporated into a microstructure model. By applying a supercell approach that randomly generates and averages stacking sequences based on transition probabilities and combining it with a grid search algorithm, the microstructures, i.e. the degrees of faulting in the structures of the title compounds were refined to the measured XRPD data. In result the crystal structures of Ag3LiIr2O6 and Ag3LiRu2O6 were found to be vastly faulted with almost no coherence of the stacked layers.

The occurrence of a unique 3D nanoscale network in Ni–Cr–S, treated via spark-plasma sintering, was discovered with a variety of ex situ and in situ TEM and XRD techniques. The starting material, consisting of a heterogeneous mixture of different phases, could be purified upon application of the sintering process. The obtained samples showed a network of chemically segregated domains being either Ni rich and Cr deficient or vice versa. These domains could be proven to intergrow fully coherently in 3D, thus establishing a unique microstructure. Electron beam irradiation caused the initial Cr3S4-type structures to transform into the disordered NiAs-type. The disordering is characterised by significant short-range ordering as indicated by the appearance of prominent diffuse scattering. Thermoelectric characterisation at room temperature indicated an n-type semiconductor behaviour with thermal and electrical conductivities similar to usual thermoelectric materials, however with a low Seebeck coefficient and a low power factor of 49.3 μW m−1 K−2.

Tuning the chemical composition and structure for targeted functionality in two-dimensional (2D) nanosheets has become a major objective in the rapidly growing area of 2D materials. In the context of photocatalysis, both miniaturization and extending the light absorption of UV active photocatalysts are major assets. Here, we investigate the solid solution between two photocatalytic systems known from literature to evolve H-2 from water/methanol under UV-RbCa2Nb3O10 (E-g = 3.7 eV) -and visible light irradiation - RbPb2Nb3O10 (E-g = 3.0 eV) - by synthesizing hypothetical RbCa2-xPbxNb3O10. While the calcium niobate can easily be exfoliated into individual nanosheets via cation-proton exchange and subsequent treatment with tetra-n-butyl-ammonium hydroxide (TBAOH), the lead niobate barely yields nano-sheets. Spectroscopic and microscopic analysis suggest that this is caused by volatilization of Pb during synthesis, leading to a local 3D linkage of RbPb2Nb3O10 perovskite units with Pb deficient units. On the one hand, this linkage progressively prevents exfoliation along with an increasing Pb content. On the other hand, introducing Pb into the perovskite blocks successively leads to bandgap narrowing, thus gradually enhancing the light harvesting capability of the solid solution. Finding a compromise between this narrowing of the bandgap and the possibility of exfoliation, visible light sensitized nanosheets can be engineered in good yield for an initial molar ratio of Ca:Pb >= 1:1.

Novel anodes for Li-ion batteries have been characterized by transmission electron microscopy (TEM). The anodes consist of arrays of ordered silicon microwires obtained from conventional silicon wafers by controlled etching processes. Suitable preparation methods for wires in the micrometer range have been tested, optimized, and subsequently applied. Ex situ TEM measurements have been performed for pristine as well as for electrochemically cycled wires that have been charged and discharged for several times. The influences of cycling rate, an electrolyte additive, as well as elevated temperatures on the anodes’ stability have been investigated.

The discovery of 2D forms of matter, pioneered by graphene, has not only triggered new insights into fundamental physics but also pushed the limits of miniaturization. To process nanosheets into ultrathin functional devices, the development of scalable exfoliation routes is of key interest. Here, we demonstrate for the first time a mild, yet highly effective silver-ion-based exfoliation route for layered transition metal oxides. Single layer transition metal oxide nanosheets were obtained by applying silver ion exchange and subsequent treatment of the silver-intercalated phases with an aqueous suspension containing organic iodides. This generic exfoliation route can be widely applied also to acid-sensitive materials and allows the modification of the nanosheets with non-conventional organic ligands, which owing to their chemical functionality may be used to tailor the optoelectronic and surface properties of the nanosheet–ligand hybrid.

3D networks of Al-doped ZnO tetrapods decorated with ZnAl

Powder samples of Ag3LiIr2O6 and Ag3LiRu2O6 were synthesized from α-Li2IrO3 and Li2RuO3 respectively by ion exchange in an AgNO3 melt. The crystal structures of the title compounds were solved from high resolution laboratory X-ray powder diffraction (XRPD) patterns and from pair distribution function (PDF) analysis using synchrotron X-ray powder diffraction data. In both crystal structures edge sharing LiO6/3- and (Ir/Ru)O6/3-octahedra form honeycomb like layers that are stacked in a staggered fashion. Silver cations, situated in-between the layers mediate the interlayer interactions by linear O-Ag-O bonds. Anisotropic peak broadening in the XRPD patterns and diffuse scattering occurring as streaks in the precession electron diffraction (PED) patterns indicate the presence of stacking faults, which could be also visualized by high resolution transmission electron microscopy (HRTEM). Possible alternative stacking sequences were derived from the ideal crystal and incorporated into a microstructure model. By applying a supercell approach that randomly generates and averages stacking sequences based on transition probabilities and combining it with a grid search algorithm, the microstructures, i.e. the degrees of faulting in the structures of the title compounds were refined to the measured XRPD data. In result the crystal structures of Ag3LiIr2O6 and Ag3LiRu2O6 were found to be vastly faulted with almost no coherence of the stacked layers.

The single-step incorporation of multiple immiscible elements into colloidal high-entropy alloy (HEA) nanoparticles has manifold technological potential, but it continues to be a challenge for state-of-the-art synthesis methods. Hence, the development of a synthesis approach by which the chemical composition and phase of colloidal HEA nanoparticles can be controlled could lead to a new pool of nanoalloys with unparalleled functionalities. Herein, this study reports the single-step synthesis of colloidal CoCrFeMnNi HEA nanoparticles with targeted equimolar stoichiometry and diameters less than 5 nm by liquid-phase, ultrashort-pulsed laser ablation of the consolidated and heat-treated micropowders of the five constituent metals. Further, the scalability of the process with an unprecedented productivity of 3 grams of colloidal HEA nanoparticles per hour is demonstrated. Electrochemical analysis reveals a unique redox behavior of the particles' surfaces in an alkaline environment and a potential for future application as a heterogeneous catalyst for the oxygen evolution reaction.

Joints of three-dimensional (3D) rutile-type (r) tin dioxide (SnO2) nanowire networks, produced by the flame transport synthesis (FTS), are formed by coherent twin boundaries at (101)r serving for the interpenetration of the nanowires. Transmission electron microscopy (TEM) methods, i.e. high resolution and (precession) electron diffraction (PED), were utilized to collect information of the atomic interface structure along the edge-on zone axes [010]r, [111]r and superposition directions [001]r, [101]r. A model of the twin boundary is generated by a supercell approach, serving as base for simulations of all given real and reciprocal space data as for the elaboration of three-dimensional, i.e. relrod and higher order Laue zones (HOLZ), contributions to the intensity distribution of PED patterns. Confirmed by the comparison of simulated and experimental findings, details of the structural distortion at the twin boundary can be demonstrated.

We report on the structural alterations of the thermoelectric material CuCrS2 introduced by the removal of 1/3 of the Cu+ ions which are located between CrS2 layers. X-ray diffraction (XRD) and pair distribution function (PDF) analyses revealed a newly formed Cu0.66CrS2 phase with monoclinic symmetry and a 3a superstructure. Simultaneously, a distortion of CrS6 octahedra is observed strongly indicating the oxidation of Cr3+ → Cr4+ leading to a Jahn–Teller distortion. The structural features extracted from XRD indicate a pronounced disorder in the cationic sub-lattice at moderate temperatures (400 K). Transmission electron microscopy (TEM) examination elucidates the formation of a second Cu0.66CrS2 phase without the superstructure, caused by incipient Cu+ mobility upon beam irradiation. The synergetic combination of high temperature XRD and TEM investigations unveiled the complete mechanism of the phase transition occurring at 503 K, where a transformation into the spinel CuCr2S4 and stoichiometric CuCrS2 occurs.

Five new compounds in the Cu/P/Se phase diagram have been synthesized, and their crystal structures have been determined. The crystal structures of these compounds comprise four previously unreported zero-, one-, and two-dimensional selenidophosphate anions containing low-valent phosphorus. In addition to two new modifications of Cu4P2Se6 featuring the well-known hexaselenidohypodiphosphate(IV) ion, there are three copper selenidophosphates with low-valent P: Cu4P3Se4 contains two different new anions, (i) a monomeric (zero-dimensional) selenidophosphate anion [P2Se4](4-) and (ii) a one-dimensional selenidophosphate anion [Formula: see text], which is related to the well-known gray-Se-like [Formula: see text] Zintl anion. Cu4P4Se3 contains one-dimensional [Formula: see text] polyanions, whereas CuP2Se contains the 2D selenidophosphate [Formula: see text] polyanion. It consists of charge-neutral CuP2Se layers separated by a van der Waals gap which is very rare for a Zintl-type phase. Hence, besides black P, CuP2Se constitutes a new possible source of 2D oxidized phosphorus containing layers for intercalation or exfoliation experiments. Additionally, the electronic structures and some fundamental physical properties of the new compounds are reported. All compounds are semiconducting with indirect band gaps of the orders of around 1 eV. The phases reported here add to the structural diversity of chalcogenido phosphates. The structural variety of this family of compounds may translate into a variety of tunable physical properties.

Titanium-rich TiNiCu shape memory thin films with ultralow fatigue have been analysed for their structural features by transmission electron microscopy. The stabilization of austenite (B2) and orthorhombic martensite (B19) variants epitaxially connected to Ti2Cu-type precipitates has been observed and found responsible for the supreme mechanical cycling capability of these compounds. Comprehensiveex situandin situcooling/heating experiments have demonstrated the presence of an austenitic nanoscale region in between B19 and Ti2Cu, in which the structure shows a gradual transition from B19 to B2 which is then coupled to the Ti2Cu precipitate. It is proposed that this residual and epitaxial austenite acts as a template for the temperature-induced B2↔B19 phase transition and is also responsible for the high repeatability of the stress-induced transformation. This scenario poses an antithesis to residual martensite found in common high-fatigue shape memory alloys.

Here, we report on a new aero-material, called aero-ZnS, representing self-organized architectures made of ZnS hollow micro-tetrapod structures with nanoscale thin walls. The fabrication process is based on the hydride vapor phase epitaxy of CdS on sacrificial micro-tetrapods of ZnO with simultaneous or subsequent transformation of CdS into ZnS and removal of the sacrificial ZnO crystals. The nanostructure of the obtained ZnS hollow micro-tetrapods exhibits the polytypic intergrowth of wurtzite- and sphalerite-type phases perpendicular to their close packed planes. The inner surface of the micro-tetrapod walls preserves oxygen sites, as demonstrated by imaging based on electron energy-loss filtering. The self-organized aero-ZnS architecture proves to be hydrophilic under tension and hydrophobic when compressed against water. Self-propelled liquid marbles assembled using ZnS hollow micro-tetrapod structures are demonstrated.

Joints of three-dimensional (3D) rutile-type (r) tin dioxide (SnO2) nanowire networks, produced by the flame transport synthesis (FTS), are formed by coherent twin boundaries at (101)r serving for the interpenetration of the nanowires. Transmission electron microscopy (TEM) methods, i.e. high resolution and (precession) electron diffraction (PED), were utilized to collect information of the atomic interface structure along the edge-on zone axes [010]r, [111]r and superposition directions [001]r, [101]r. A model of the twin boundary is generated by a supercell approach, serving as base for simulations of all given real and reciprocal space data as for the elaboration of three-dimensional, i.e. relrod and higher order Laue zones (HOLZ), contributions to the intensity distribution of PED patterns. Confirmed by the comparison of simulated and experimental findings, details of the structural distortion at the twin boundary can be demonstrated.

In this work, a facile two-step fabrication and characterization of printed acetone sensors based on mixed semiconducting metal oxides is introduced. The devices are fabricated by Direct Ink Writing metal microparticle (MP) stripes of commercially available pure iron and copper particles onto the surface of a glass substrate, forming a bridging multi-phase semiconducting oxide net by subsequent thermal annealing. The open, highly porous bridging structures consist of heterojunctions which are interconnected via non-planar CuO/Cu2O/Cu nanowires and Fe2O3/Fe nanospikes. Morphological, vibrational, chemical and structural studies were performed to investigate the contact-forming Fe2O3–CuO nanostructures on the surface of the MPs. The power consumption and the gas sensing properties showed selectivity to acetone vapor at an operating temperature of around 300 °C with a high gas response of about 50% and the lowest operating power of around 0.26 μW to a concentration of 100 ppm of acetone vapor. The combination of the possibility of acetone vapor detection, the controllable size and geometry and their low power make these printed structures important candidates for next developments of accessible detection devices, as well as acetone vapor monitoring (even below 1 ppm). The printing of MPs in general paves the way for a new generation of printed different devices, even in “home-made” conditions, for a manifold of applications tailored by the composition and geometry of the printed MP stripes, enabled through the simplicity and versatility of the fabrication method.

Stabilization of covalent organic frameworks (COFs) by post-synthetic locking strategies is a powerful tool to push the limits of COF utilization, which are imposed by the reversible COF linkage. Here we introduce a sulfur-assisted chemical conversion of a two-dimensional imine-linked COF into a thiazole-linked COF, with full retention of crystallinity and porosity. This post-synthetic modification entails significantly enhanced chemical and electron beam stability, enabling investigation of the real framework structure at a high level of detail. An in-depth study by electron diffraction and transmission electron microscopy reveals a myriad of previously unknown or unverified structural features such as grain boundaries and edge dislocations, which are likely generic to the in-plane structure of 2D COFs. The visualization of such real structural features is key to understand, design and control structure–property relationships in COFs, which can have major implications for adsorption, catalytic, and transport properties of such crystalline porous polymers., Stabilization of covalent organic frameworks (COFs) by post-synthetic locking is a powerful tool to push the limits of COF utilization. Here the authors demonstrate a sulfur-assisted conversion of an imine-linked COF into a thiazole-linked COF, with retention of crystallinity and porosity, allowing for direct imaging of defects in COFs.

By establishing magnetic order in a square lattice compound, we introduce the first magnetic “new fermion.”, Recent interest in topological semimetals has led to the proposal of many new topological phases that can be realized in real materials. Next to Dirac and Weyl systems, these include more exotic phases based on manifold band degeneracies in the bulk electronic structure. The exotic states in topological semimetals are usually protected by some sort of crystal symmetry, and the introduction of magnetic order can influence these states by breaking time-reversal symmetry. We show that we can realize a rich variety of different topological semimetal states in a single material, CeSbTe. This compound can exhibit different types of magnetic order that can be accessed easily by applying a small field. Therefore, it allows for tuning the electronic structure and can drive it through a manifold of topologically distinct phases, such as the first nonsymmorphic magnetic topological phase with an eightfold band crossing at a high-symmetry point. Our experimental results are backed by a full magnetic group theory analysis and ab initio calculations. This discovery introduces a realistic and promising platform for studying the interplay of magnetism and topology. We also show that we can generally expand the numbers of space groups that allow for high-order band degeneracies by introducing antiferromagnetic order.