Type Crystal Structure Research Articles

Novel 2D Material of MBenes: Structures, Synthesis, Properties, and Applications in Energy Conversion and Storage.

2D transition metal borides (MBenes) have garnered significant attention from researchers due to their exceptional electrical conductivity, strong mechanical rigidity, excellent dynamic and thermodynamic stability, which stimulates the enthusiasm of researchers for the study of MBenes. Over the past few years, extensive research efforts have been dedicated to the study of MBenes, resulting in a growing number of synthesis methods being developed. However, there remains a scarcity of comprehensive reviews on MBenes, particularly in relation to the synthesis techniques employed. To address this gap, this review aims to provide a comprehensive summary of the latest research findings on MBenes. An exhaustive exploration of the crystal structure types of MBenes is presented, highlighting the greater structural diversity compared to MXenes. Furthermore, a comprehensive review of the recent advancements in MBenes synthesis methodologies is provided. The review also delves into the physical and chemical properties of MBenes, while elucidating their applications in the realms of energy conversion and energy storage. Lastly, this review concludes by summarizing and offering insights on MBenes from three angles: synthesis, structure-property relationships, and application prospects.

Crystal structure and magnetic properties of Yb2Pt2Pb under multi-extreme conditions

ABSTRACT Structural and magnetic properties of the Shastry-Sutherland material Yb2Pt2Pb were studied in single-crystalline form under pressures up to 10 GPa, magnetic fields up to 17 T, and temperatures down to 0.3 K. Surprisingly robust magnetic order is observed with the Néel temperature T N = 2.1 K stable up to 8.1 GPa. Indication of an additional magnetic phase formation can be traced in resistivity data for magnetic field along the c-axis exceeding the (pressure-dependent) metamagnetic transition. The related anomaly shifts to higher temperatures with increasing field, merging T N at the tricritical point. Experiments with μ0 H // [110] revealed the pressure stabilization of observed magnetic phases with respect to the magnetic field. The crystal-structure type is stable up to 10 GPa, without any sign of symmetry change, exhibiting moderate volume compressibility with bulk modulus B = 116(13) GPa, in good agreement with B = 118 GPa provided by the density functional theory.

Two pressure-induced molecular superconductors with different types of crystal and electronic structures derived from an unsymmetrical tetrachalcogenafulvalene

Abstract We newly synthesized an organic donor molecule ETTM-STF (ethylenedithio(trimethylene)diselenadithiafulvalene), a molecular hybrid of HMTTF (hexamethylenetetrathiafulvalene) and BETS (bis(ethylenedithio)tetraselenafulvalene). Electrochemical oxidation of ETTM-STF provided two cation radical salts, (ETTM-STF)2Au(CN)2 and (ETTM-STF)2BF4. Crystal structure of the Au(CN)2 salt is characterized by a monolayer structure based on dimerized donor molecules. On the other hand, the BF4 salt shows a bilayer structure that is composed of two crystallographically independent conducting layers with different types of electronic structures. At ambient pressure, the Au(CN)2 salt is a Mott insulator and the BF4 salt undergoes a metal–nonmetal transition where the two types of conducting layers exhibit different behavior. Application of pressure suppressed the nonconducting behavior and induced a superconducting state in the Au(CN)2 salt (Tc = 3.4 K at 9.5 kbar) and in the BF4 salt (Tc = 6.8 K at 8 kbar).

Effect of Sourdough-Yeast Co-Fermentation on Physicochemical Properties of Corn Fagao Batter.

Fagao is one of China's traditional gluten-free staple foods made with rice or corn flour. Corn Fagao prepared by co-fermentation with sourdough and yeast exhibits better quality and less staling compared to traditional yeast-fermented Fagao. The physicochemical properties of corn Fagao batter during sourdough-yeast co-fermentation were investigated. The results showed that compared with yeast fermentation, the gas production and viscosity of the batter increased with co-fermentation. The co-fermented batter showed a higher hydrolysis of starch and less amylose content. The integrity of starch granules in the co-fermented batter was damaged more seriously, and the crystallinity and short-range ordered structure were less than in the yeast-fermented batter, even though the crystal structure type of starch did not obviously change. The peak viscosity, minimum viscosity, final viscosity, decay value, and recovery value of the corn batter were reduced by co-fermentation, which improved the thermal stability of the batter and slowed down the aging. Co-fermentation also resulted in a more pronounced reduction in protein subunit content than yeast fermentation. The changes in the physicochemical properties of the corn Fagao batter help explain the improvement in quality of corn Fagao made from the co-fermentation method and may provide theoretical references for co-fermentation with sourdough and yeast to other gluten-free foods.

Enhanced magnetic refrigeration capacities of Er6FeSb2 by manganese substitution

Er6FeSb2 is a potential magnetic refrigeration material that can work at the liquid hydrogen temperature range. This work enhances the magnetic refrigeration performance of Er6Fe1-xMnxSb2 by Mn substitution. Mn doping increases the cell volume while maintaining the compound’s crystal structure type. It also results in an increase in the charge density distribution between Er1 and Fe/Mn. As the Mn content increases, the ferromagnetic exchange is enhanced, and the TC continuously increases. The Mn doping induces spin reorientation at low temperature, transforming compounds from traditional magnetocaloric effects to table-like magnetocaloric effects, greatly enlarge the cooling temperature range. When the content of Mn increases from x = 0 to x = 0.3, the δTFWHM increases from 26 K to 62 K, the −(ΔSM)max decreases from 12.1 J/(kg·K) to 5.9 J/(kg·K), and the RCP first increases and then decreases, reaching the maximum value of 435.0 J/kg at x = 0.2. This study opens a new path for the search of magnetic refrigeration material with large cooling temperature range.

Investigation of the effects of graphene on Al0.3CoCrFeNi high entropy alloy/3graphene composite materials based on different crystal structures

The influence of graphene layers and crystal structure types on the nanoindentation reinforcement mechanism of Al0.3CoCrFeNi high-entropy alloy/graphene (HEA/Gp) composite materials was studied using molecular dynamics (MD) simulations. The results indicate that the influence of graphene layers on composite materials is related to the position of the indenter. Before the indenter contacts the graphene layer, some dislocations are absorbed by the graphene, unable to form dislocation cells and dislocation locks to hinder the deformation of the matrix, resulting in the hardness of the composite material being lower than that of the HEA matrix. After the indentation contacts the graphene layer, dislocations can penetrate the graphene to form a high-density dislocation cell. Due to graphene's excellent deformation resistance, the composite material's load-bearing capacity is much greater than that of the HEA matrix. In addition, stress propagates along the grain boundaries in polycrystalline and twinned polycrystalline structures. Grain boundaries decrease the material strength, while twinned boundaries can refine grain size and enhance grain stability. Additionally, composite materials' elastic recovery increases first and then decreases with the increase in graphene layers and twinning. The hardness of the material shows an anomalous phenomenon about grain size following a Hall-Petch relationship. When the angle between graphene layers is 0, the stress distribution inside the material is most uniform.

New stable transition metal carbonitrides: TM3C2N, TM3CN2, and TM4C3N

Transition metal carbonitrides have been widely applied in various fields due to their excellent physical and chemical properties. In the pursuit of identifying innovative and stable crystal structures among transition metal carbonitrides, we have employed first-principles calculations to investigate the substitution of transition metal elements (Cr, Hf, Mo, Nb, Ti, V, W, Zr) for Ta within three stable crystal structure types: Ta3C2N, Ta3CN2, and Ta4C3N. The thermal stability, dynamic stability, and mechanical stability of these twenty-four structures were systematically studied, and nine stable new crystal structures were finally identified. Our subsequent investigations have included assessments of their structural, electrical, and mechanical properties. Our findings in mechanical properties have revealed that five compounds, Nb3CN2, Hf4C3N, Nb4C3N, Ti4C3N, and Zr4C3N, exhibit hardness values of 20.3 GPa, 30.0 GPa, 22.4 GPa, 28.7 GPa, and 26.2 GPa, respectively. Furthermore, our electronic property assessments have indicated that these structures exhibit metallic characteristics.

An Advanced Methodology for Crystal System Detection in Li-ion Batteries

Detecting the crystal system of lithium-ion batteries is crucial for optimizing their performance and safety. Understanding the arrangement of atoms or ions within the battery’s electrodes and electrolyte allows for improvements in energy density, cycling stability, and safety features. This knowledge also guides material design and fabrication techniques, driving advancements in battery technology for various applications. In this paper, a publicly available dataset was utilized to develop mathematical equations (MEs) using a genetic programming symbolic classifier (GPSC) to determine the type of crystal structure in Li-ion batteries with a high classification performance. The dataset consists of three different classes transformed into three binary classification datasets using a one-versus-rest approach. Since the target variable of each dataset variation is imbalanced, several oversampling techniques were employed to achieve balanced dataset variations. The GPSC was trained on these balanced dataset variations using a five-fold cross-validation (5FCV) process, and the optimal GPSC hyperparameter values were searched for using a random hyperparameter value search (RHVS) method. The goal was to find the optimal combination of GPSC hyperparameter values to achieve the highest classification performance. After obtaining MEs using the GPSC with the highest classification performance, they were combined and tested on initial binary classification dataset variations. Based on the conducted investigation, the ensemble of MEs could detect the crystal system of Li-ion batteries with a high classification accuracy (1.0).

Intermetallic compounds in equilibrium with aluminum in Al–Ca–Cu ternary alloying system

The structure and properties of the new (Al,Cu)4Ca, Al27Ca3Cu7, and Al8CaCu4 intermetallic compounds in equilibrium with aluminum solid solution in the ternary Al–Ca–Cu alloying system were comprehensively analyzed. The (Al,Cu)4Ca intermetallic compound is treated as a line phase based on the Al4Ca phase with Cu substituted by Al. The solubility of copper in the compound reaches 10 at.% (19 wt.%), which leads to marked changes in the crystal lattice structure, physical and mechanical properties of the compound. For instance, the density of the compound increases from 2.22 to 2.79 g/cm3 and the microhardness from HV 180 to HV 250. The Al27Ca3Cu7 phase is treated as a strict stoichiometric ternary compound with a primitive BaHg11 type crystal structure of the Pm3m space group. The lattice parameter is accepted to be 8.514 Å corresponding to a density of 3.45 g/cm3. The Al8CaCu4 phase is also a strict stoichiometric ternary compound with a tetragonal crystal lattice structure of the Mn12Th type. The phase has the highest microhardness (HV 505) and density (4.57 g/cm3). The alloys pertaining to the binary (Al)+(Al,Cu)4Ca phase field and the quasi-binary (Al)+Al27Ca3Cu7 section can be considered promising as the base for new natural aluminum matrix composites.

Structural Properties of Thermoluminescence Dosimeter Materials, Preparation, Application, and Adaptability: A Systematic Review

Thermoluminescence dosimeters (TLDs) are widely used in radiation dosimetry due to their excellent properties, such as high sensitivity, small size, and ability to measure low doses of radiation. This review focuses on the structural properties of TLD materials, as well as their preparation, application, and adaptability. The review covers the various types of TLD materials, crystal structure, and properties, including energy response and fading characteristics. The different methods used to prepare TLD materials, such as solid-state synthesis, sol-gel synthesis, and solution growth methods, are discussed in detail. The review also includes a detailed discussion of the various applications of TLDs, including medical, environmental, and industrial radiation dosimetry. Extensive information on TLD is reviewed, and the TL characteristics that have a noticeable impact on the TL dosimetry potential for human and other purpose utilisation, such as mineral, oil, and gas resource investigation, can be done using natural and artificial TL signals. Information on TL measurement process requirements and the TL characteristics that have a noticeable impact on a compound TL dosimetry potential are also addressed. Finally, the review concludes by highlighting the adaptability of TLD materials to different dosimetry applications and their potential use in the future.

Griffiths phase like behaviour in CoCrVZ (Z = Al, Ga) Heusler alloys

We report here the studies of structural and magnetic properties of two equiatomic quaternary Heusler alloys CoCrVZ (Z = Al, Ga). Both the alloys crystallize in LiMgPdSn type crystal structure (space group #216) with B2 (CoCrVAl) and A2 (CoCrVGa) type anti-site disorder between elemental sites. Intended stoichiometry was confirmed from the compositional analysis. The temperature dependence of dc magnetic susceptibility and the low temperature moment values show a nearly compensating ferrimagnetic behaviour at low temperatures for both the alloys. The inverse of dc magnetic susceptibility starts to deviate from the Curie–Weiss law below 220 K and 164 K for the alloys containing Al and Ga respectively. The Arrott plots confirms the absence of long range order down to 2 K. Further analysis of the dc and ac susceptibility shows that the observed behaviour is due to the presence of Griffiths like phase in these alloys.

DNA binding reveals hidden interdomain allostery of a MazE antitoxin from Mycobacterium tuberculosis

Type II toxin−antitoxin (TA) systems are ubiquitously distributed genetic elements in prokaryotes and are crucial for cell maintenance and survival under environmental stresses. The antitoxin is a modular protein consisting of the disordered C-terminal region that physically contacts and neutralizes the cognate toxin and the well-folded N-terminal DNA binding domain responsible for autorepression of TA transcription. However, how the two functional domains communicate is largely unknown. Herein, we determined the crystal structure of the N-terminal domain of the type II antitoxin MazE-mt10 from Mycobacterium tuberculosis, revealing a homodimer of the ribbon-helix-helix (RHH) fold with distinct DNA binding specificity. NMR studies demonstrated that full-length MazE-mt10 forms the helical and coiled states in equilibrium within the C-terminal region, and that helical propensity is allosterically enhanced by the N-terminal binding to the cognate operator DNA. This coil-to-helix transition may promote toxin binding/neutralization of MazE-mt10 and further stabilize the TA–DNA transcription repressor. This is supported by many crystal structures of type II TA complexes in which antitoxins form an α-helical structure at the TA interface. The hidden helical state of free MazE-mt10 in solution, favored by DNA binding, adds a new dimension to the regulatory mechanism of type II TA systems. Furthermore, complementary approaches using X-ray crystallography and NMR allow us to study the allosteric interdomain interplay of many other full-length antitoxins of type II TA systems.

Atom pair bond approach: an efficient method for determining the lattice parameters of NiAs-type compounds and comparative analysis with computational databases

Comparison of EOS properties such as lattice parameters, bulk modulus, etc calculated by density functional theory (DFT) with experiments is used, in general, to assess the precision reachable in computations, when using different codes and potentials. DFT calculations using a large number of codes and potentials by different groups, have reported excellent precision (0.02 Å) in the lattice parameters of 71 elements. It is of interest to study the precision levels reachable in compounds of hexagonal NiAs type crystal structure, in which a wide range of electrical conductivity and magnetic order are found to occur. In this study, lattice parameters for 42 intermetallic compounds of the NiAs type structure are determined from internal radii using the Atom Pair Bond method. These values are compared with the lattice parameters reported from the high throughput DFT computational techniques such as AFLOW and Materials Project compilations. Precision in lattice parameters obtainable in the three methods is assessed in comparison with those reported from the experiments. Selection of a set of compounds of same crystal structure brings out the role of differences in the electronic structure of elements involved. In the APB method, lattice parameters are obtained by the best-fit equations defined by radii change in a large number of compounds with a particular structure, and do not involve several approximations, unlike in DFT. It is interesting to see that the simple APB approach could estimate lattice parameters with accuracies comparable to DFT methods.

Thickness dependence of structural and magnetic properties of electrodeposited Co2FeSn films

Co2FeSn films have been electrochemically deposited on polycrystalline Cu substrates in potentiostatic mode. Processed films with thicknesses of 320 nm, 780 nm, and 1400 nm exhibited highly ordered L21 type crystal structure with saturation magnetizations of 1023.38 kA/m (5.08 ± 0.04 μB/f.u.), 1035.31 kA/m (5.14 ± 0.04 μB/f.u.) and 1044.34 kA/m (5.18 ± 0.04 μB/f.u.) at 5 K and 965.00 kA/m (4.79 ± 0.04 μB/f.u.), 967.75 kA/m (4.81 ± 0.04 μB/f.u.), and 1003.52 kA/m (4.97 ± 0.04 μB/f.u.) at 300 K, respectively. The soft ferromagnetic films possess coercivity of ∼ 15.92 kA/m (200 Oe) with a high effective anisotropy constant of ∼ 105 J/m3. Thermo-magnetization measurements yielded high Curie temperatures of 995 K, 1005 K, and 1123 K for films of thicknesses 320 nm, 780 nm, and 1400 nm, respectively. Tailoring the thickness from 320 to 1400 nm could be achieved by merely varying the electrodeposition time without appreciable departure from chemical stoichiometry or compromise in crystalline order or magnetic properties. This establishes a methodology to prepare high quality L21 ordered Co2FeSn films with a few hundred nanometers thickness by electrodeposition. Electrodeposited Co2FeSn films with high magnetic moment, high Keff value, and high Curie temperature are potential candidates for fabricating nanomagnetic devices.

Phase Relation and Equation of State of Iron‐Titanium Oxyhydroxides With α‐PbO2 Type Crystal Structure at Deep Mantle Conditions

AbstractPhase relation and equation of state of iron‐titanium oxyhydroxide with α‐PbO2‐type crystal structure (hydrous α‐phase) was investigated at pressure from middle upper mantle to mantle transition zone. The experiments were performed using multi‐anvil apparatus with in situ synchrotron X‐ray diffraction. The metal‐diamond sample container was used to maintain a closed system with respect to water while allowing X‐ray transmittance. Starting materials were mixture of reagent grade goethite and anatase with Fe:Ti = 1:1 and 1:3. The hydrous α‐phase was synthesized at 11–14 GPa and 800–900°C. The X‐ray diffraction data were obtained over a wide range of pressures from 5 to 22 GPa and temperatures from room temperature to 930°C. Using pressure‐volume‐temperature data of the hydrous α‐phase with Fe:Ti = 1:1 collected at room temperature to 800°C and at 8.9–20.8 GPa, we determined the isothermal bulk modulus (KT0 = 183 (1) GPa) and the thermal expansivity (α0 = 3.29 (1) × 10−5K−1) at ambient condition. The stability field of the hydrous α‐phase and phase relation of FeOOH‐TiO2 system at 900°C was well constrained. It was found that the hydrous α‐phase decomposes into baddeleyite‐type TiO2 + ε‐FeOOH at pressure of approximately 20–21 GPa, and into ilmenite + rutile at 5–6 GPa. This stability field equivalent to depth of 180–600 km in the subduction zone. Our results suggest that the hydrous α‐phase is an important water reservoir in the middle upper mantle to mantle transition zone.

Crystal-Structure Control of Molecular Semiconductors by Methylthiolation: Toward Ultrahigh Mobility.

ConspectusThe crystal structure of organic semiconductors has been regarded as one of the crucial factors for realizing high-performance electronic devices, such as organic field-effect transistors. However, although the control of crystal structures of organic semiconductors has been examined in the last two decades of intensive efforts of the development of organic semiconductors, active measures to control crystal structures enabling high carrier mobility are still limited. In 2016, our research group noticed that regioselective methylthiolation could provide a selective crystal structure change from an ordinary herringbone structure to a pitched π-stacking structure, similar to the crystal structure of rubrene, in the benzo[1,2-b:4,5-b']dithiophene (BDT) system. Following this serendipitous finding, our group systematically investigated the relationship between the molecular and crystal structures of a range of methylthiolated aromatic and heteroaromatic compounds.This Account provides a comprehensive overview of our research efforts and advancements in the development of methylthiolated small-molecule-based organic semiconductors (molecular semiconductors). We first describe the outline of the past development of molecular semiconductors, focusing on the types of crystal structures of high-performance molecular semiconductors. Then, we describe our findings on the drastic crystal structure change in the BDT system upon methylthiolation, detailing the causes of the change in terms of the intermolecular contacts and intermolecular interaction energies. This is followed by the confirmation of the generality of the crystal-structure change by methylthiolation of a series of acene and heteroacenes, where the herringbone structure in the parent system is unexceptionally transformed into the pitched π-stacking structure, a promising crystal structure for high-mobility molecular semiconductors well exemplified by the prototypical molecular semiconductor, rubrene. In fact, the methylthiolated anthradithiophene afforded comparable high mobility to rubrene in single-crystal field-effect transistors. Then, we demonstrate that the sandwich herringbone structures of peri-condensed polycyclic aromatic hydrocarbons, including pyrene, perylene, and peropyrene, change into brickwork crystal structures upon methylthiolation and that, among these compounds, very promising molecular semiconductors, methylthiolated pyrene and peropyrene, showing ultrahigh mobility of 30 cm2 V s-1, are realized.Through the studies, by gaining insights into the underlying mechanisms driving the crystal structure changes, we lay a strong foundation for tackling challenges related to controlling the crystal structures and developing high-performance molecular semiconductors. This will be a distinct approach from the past activities in the development of molecular semiconductors that mainly focused on molecules themselves, including their synthesis, properties, and characterization. We thus anticipate that our findings and the present Account will open the door to a new era of the development of molecular semiconductors.

Kristjánite, KNa2H(SO4)2, a new fumarolic mineral from Iceland containing the [SO4–H–SO4]3– anion in the crystal structure

Abstract Kristjánite, KNa2H(SO4)2, is a new mineral (IMA2022–131) found in a high-temperature fumarole on Fimmvörðuháls, Iceland. It is monoclinic, P21/n, a = 6.9625(1), b = 9.9953(1), c = 11.0928(2) (Å), β = 105.637(2)° and V = 743.40(2) Å3. Kristjánite forms colourless transparent crystals up to ~100 μm in size in compact aggregates with metathénardite, belomarinaite, aphthitalite, ivsite and an unknown mineral with tentative composition K2NaH(SO4)2, or grows in white globules of smaller grains on their surface. The eight strongest maxima in a powder X-ray diffraction diagram are [d, Å (Intensity)] 4.37 (59), 3.65 (32), 3.48 (78), 3.36 (100), 3.18 (76), 2.83 (43), 2.73 (38) and 2.405 (23). The mineral represents a novel crystal structure type. In it, K is coordinated by eight O atoms, and two symmetrically independent Na atoms by seven O atoms. Two symmetrically independent S atoms are in tetrahedral coordination by O atoms. A close to linear, very short hydrogen bond (2.44 Å), connects the two to a SO4–H–SO4 dimer. K and Na coordination polyhedra share vertices, edges and even faces forming with sulfate tetrahedra a tight structure with narrow [100] channels lined on two opposite sides by hydrogen bonds.

Ultrahigh Degree of Cationic Disorder, Configurational Entropy in New Type of High-Entropy Pseudobrookite Phase.

High-entropy ceramics exhibit various excellent properties owing to their high configurational entropy, which is caused by multi-principal elements sharing one lattice site. The configurational entropy will further increase significantly if multi-principal elements randomly share two different lattice sites. For this purpose, pseudobrookite phase containing two cationic lattice sites (A and B sites) is selected, and corresponding high-entropy pseudobrookite (M2+ 0.4M3+ 1.2)Ti1.4O5 is synthesized. Herein, the distribution of the 2-valent and 3-valent cations in the A and B sites are analysed in depth. The distance between the A and B sites in the crystal structure models which are constructed by the Rietveld analysis is calculated and defined as distance d. Meanwhile, the atomic column positions in the STEM images are quantified by a model-based mathematical algorithm, and the corresponding distance d are calculated. By comparing the distance d, it is determine that the 2-valent and 3-valent cations are jointly and disorderly distributed in the A and B sites in high-entropy (M2+ 0.4M3+ 1.2)Ti1.4O5. The density functional theory (DFT) simulations also demonstrate that this type of crystal structure is more thermodynamically stable. The higher degree of cationic disorder leads to a higher configurational entropy in high-entropy (M2+ 0.4M3+ 1.2)Ti1.4O5, and endows high-entropy (M2+ 0.4M3+ 1.2)Ti1.4O5 with very low thermal conductivity (1.187-1.249Wm-1K-1).

Li2GeS3: New Structural Type of Lithium Solid Electrolyte for All-Solid-State Batteries

Sulfide inorganic materials exhibit favorable qualities such as high ionic conductivity and mechanical softness, making them promising candidates for solid electrolytes in Li-ion all-solid-state batteries. Sulfide solid electrolytes exist in various structural types, including β-Li3PS4, Li10GeP2S12, argyrodite, Li4PS4I, Li7P3S11, and Li1.82SiP0.036S3. While these materials exhibit high ionic conductivities of up to ~10− 2 S cm− 1 at room temperature and possess mechanical softness, they also have limitations, such as a narrow electrochemical stability window and air instability, which can hinder their scalability. The electrochemical and air stabilities of a solid electrolyte (Li–M–S, where M = non-Li metal ions) are largely governed by its stability of crystal structure consisting of MSn polyhedra and Li ions. A material with a different crystal structure would show its distinct properties. However, despite extensive research, no single structure known to date has proven superior in all aspects of performance. Given the importance of crystal structure in developing high-performance solid electrolytes, exploring and identifying novel ion-conducting materials with unique crystal structures is imperative. Additionally, once a new structural type of material is discovered, its performance can be adjusted, enhanced, or optimized through various techniques, such as chemical substitution, morphology and particle size control, and surface coating. In this work, we discovered a new crystal structural type of Li-ion conductor Li2GeS3. It was first known in 2000 by Kanno et al., with only orthorhombic unit cell dimension reported. However, our study using ab initio structure determination techniques from powder X-ray diffraction data, similar to our previous works, unveiled its structure possessing a hexagonal P61 symmetry with lattice parameters of a = 6.80098(4) Å and c = 17.92827(11) Å, revealing a new type of crystal structure. Its structure is comprised of a distorted hexagonal close-packed arrangement of sulfur anions with three asymmetric metal atoms: Ge and Li2 are in tetrahedral cavities surrounded by sulfur atoms; Li1 is in the trigonal bipyramidal cavity. The material displayed an ionic conductivity of 1.63 × 10− 8 S cm− 1 at 303 K and 2.45 × 10− 7 S cm− 1 at 383 K. Bond valence energy landscape calculations revealed three-dimensional lithium diffusion pathways within the structure. These results suggest that Li2GeS3 is expected to be a host structure from which improved ionic conductors can be derived through appropriate chemical substitution.

A Deeper Insight into Stability of Pt-Alloy Nanoparticles as Oxygen Reduction Reaction Electrocatalysts

One of the links in the chain of creating a carbon-neutral society is undoubtedly hydrogen-powered vehicles. However, due to a very high price of platinum (Pt), which is used as an electrocatalyst for the hydrogen oxidation reaction (HOR) at the anode, as well as the oxygen reduction reaction (ORR) at the cathode of the proton exchange membrane fuel cell (PEMFC), their massive production is still unfeasible. Moreover, a very slow kinetics of the ORR and consequently the need for larger quantities of electrocatalyst makes this issue even higher. Therefore, in the fuel cell community there is a lot of effort to reduce the use of Pt. The most promising solution on that path seems to be carbon supported Pt-based nanoalloys, where part of Pt is replaced by a less noble and at the same time less expensive metal (e.g. Co, Cu, Fe, Ni).1 Nevertheless, although the ORR activity of carbon supported Pt-based alloys has been extensively studied and already proven, their stability is still an unsolved area. Here will be presented the latest findings regarding the stability of the carbon supported intermetallic Pt-alloy nanoparticles (Pt-M/C, where M = Co, Cu or Ni) obtained by utilization of advanced, in-house designed methodologies such as the high-temperature accelerated degradation tests (HT-ADTs) and the high-temperature electrochemical flow cell coupled to an inductively coupled plasma mass spectrometry (HT-EFC-ICP-MS).2,3 Whereas the former enables ADT to be performed in a liquid electrolyte half-cell using a standard rotating disk electrode at temperatures of up to 80 °C, the latter allows for precise (ppb range) time-temperature-and-potential resolved measurements of dissolution of metals. By simulating close-to-real operational conditions, these technologies enabled to show that in addition to the carbon corrosion, which follows the Arrhenius law and increases exponentially with temperature,3,4 also Pt dissolution, as well as less noble metal dissolution, increases with increasing temperature.2,3 However, with an increase in temperature, not only the dissolution of Pt, but also the rate of its re-deposition (due to the Ostwald ripening) is increased at the same time.2,3,5 Furthermore, the widening of the potential window results in an exponential growth of temperature impact on metals dissolution.2,3 These previous findings about the dependence of the stability of Pt and less noble metal on the temperature and potential window2 will be upgraded with new information about the impact of some other non-intrinsic as well as intrinsic properties on the stability of metal nanoparticles in the carbon supported Pt-nanoalloys. In other words, the effect of a different number of cycles of the degradation tests on the behavior of Pt and less noble metal in the operational potential window (i.e. 0.6-0.95 V) at the high temperature (60 °C) will be presented. In continuation, the influence of the type of crystal structure on the stability of Pt-alloy nanoparticles will also be discussed. References 1 L. J. Moriau, A. Hrnjić, A. Pavlišič, A. R. Kamšek, U. Petek, F. Ruiz-Zepeda, M. Šala, L. Pavko, V. S. Šelih, M. Bele, P. Jovanovič, M. Gatalo, N. Hodnik, iScience 2021, 102102.2 T. Đukić, L. J. Moriau, L. Pavko, M. Kostelec, M. Prokop, F. Ruiz-Zepeda, M. Šala, G. Dražić, M. Gatalo, N. Hodnik, ACS Catal. 2022, 12, 101–115.3 T. Đukić, L. Pavko, P. Jovanovič, N. Maselj, M. Gatalo, N. Hodnik, Chem. Commun. , DOI:10.1039/d2cc05377b.4 N. Maselj, M. Gatalo, F. Ruiz-Zepeda, A. Kregar, P. Jovanovič, N. Hodnik, M. Gaberšček, J. Electrochem. Soc. 2020, 167, 114506.5 A. Kregar, M. Gatalo, N. Maselj, N. Hodnik, T. Katrašnik, J. Power Sources 2021, 514, 230542.