Unique Atomic Arrangement Research Articles

Structure of a subnanometer-sized semiconductor Cd14Se13 cluster

Structure of a subnanometer-sized semiconductor Cd14Se13 cluster

A Review of the Preparation, Machining Performance, and Application of Fe-Based Amorphous Alloys

Amorphous alloy is an emerging metal material, and its unique atomic arrangement brings it the excellent properties of high strength and high hardness, and, therefore, have attracted extensive attention in the fields of electronic information and cutting-edge products. Their applications involve machining and forming, make the machining performance of amorphous alloys being a research hotspot. However, the present research on amorphous alloys and their machining performance is widely focused, especially for Fe-based amorphous alloys, and there lacks a systematic review. Therefore, in the present research, based on the properties of amorphous alloys and Fe-based amorphous alloys, the fundamental reason and improvement method of the difficult-to-machine properties of Fe-based amorphous alloys are reviewed and analyzed. Firstly, the properties of amorphous alloys are summarized, and it is found that crystallization and high temperature in machining are the main reasons for difficult-to-machine properties. Then, the unique properties, preparation and application of Fe-based amorphous alloys are reviewed. The review found that the machining of Fe-based amorphous alloys is also deteriorated by extremely high hardness and chemical tool wear. Tool-assisted machining, low-temperature lubrication assisted machining, and magnetic field-assisted machining can effectively improve the machining performance of Fe-based amorphous alloys. The combination of assisted machining methods is the development trend in machining Fe-based amorphous alloys, and even amorphous alloys in the future. The present research provides a systematic summary for the machining of Fe-based amorphous alloys, which would serve as a reference for relevant research.

Bulky Thiolate-Protected Silver Nanocluster Ag 213 (Adm-S) 44 Cl 33 with Excellent Electrocatalytic Performance toward Oxygen Reduction

Bulky Thiolate-Protected Silver Nanocluster Ag ₂₁₃ (Adm-S) ₄₄ Cl ₃₃ with Excellent Electrocatalytic Performance toward Oxygen Reduction

Tuning electronic structure via CoS clusters for visual photocatalytic H2 production and mechanism insight

Clusters with this unique atomic arrangement and configuration are highly potential cocatalysts, but designing efficient clusters and clarifying the mechanism of action remains a challenge. Herein, CoS clusters are in-situ grown on CdS nanorods, which leads to the existence of Cd-S-Co bonds. It is found that the Cd-S-Co bonds could induce interfacial charge rearrangements. Theoretical calculations reveal that the charge redistribution of heterostructures at interfaces is conducive to modulating d-band center, reducing thermodynamic energy barriers, and improving carrier separation. The optimized CdS/CoS composite shows a great photocatalytic H2 production rate (65.7 mmol h−1 g−1), such a H2 evolution rate exceeded most reported CdS nanorods photocatalyst. This study provides an experimental and theoretical foundation for the preparation of cluster-semiconductors photocatalytic materials and explores the transfer pathway between clusters and catalysts at the atomic level, and deeply discusses the mechanism of their catalytic performance.

Imaging the facet surface strain state of supported multi-faceted Pt nanoparticles during reaction

Nanostructures with specific crystallographic planes display distinctive physico-chemical properties because of their unique atomic arrangements, resulting in widespread applications in catalysis, energy conversion or sensing. Understanding strain dynamics and their relationship with crystallographic facets have been largely unexplored. Here, we reveal in situ, in three-dimensions and at the nanoscale, the volume, surface and interface strain evolution of single supported platinum nanocrystals during reaction using coherent x-ray diffractive imaging. Interestingly, identical {hkl} facets show equivalent catalytic response during non-stoichiometric cycles. Periodic strain variations are rationalised in terms of O2 adsorption or desorption during O2 exposure or CO oxidation under reducing conditions, respectively. During stoichiometric CO oxidation, the strain evolution is, however, no longer facet dependent. Large strain variations are observed in localised areas, in particular in the vicinity of the substrate/particle interface, suggesting a significant influence of the substrate on the reactivity. These findings will improve the understanding of dynamic properties in catalysis and related fields.

A general strategy for polishing SiC wafers to atomic smoothness with arbitrary facets

SiC is essential for epitaxial growth of graphene and promises to be an ideal material for next generation high-power electronics. The electronic properties of graphene are highly dependent on the facet on which it is grown. Therefore, the selection of facet provides an extra tuning parameter to obtain its desired characteristics. As one of the key factors of growing pristine graphene on SiC wafers, their roughness requires to be atomically smooth. In this work, we present a data-driven study of the grinding, mechanical polishing and chemical mechanical polishing (CMP) procedures applied to a SiC wafer with arbitrary facets. The phenomena and principles in the polishing steps are discussed. As specific facets of SiC have unique atomic arrangements, different recipes are required for the C and Si faces and their performances are investigated. The interesting, but rarely studied (1 1‾ 05) facet is taken as an example of a non-polar case to apply the procedures. It is found that the material removal rate (MRR) in mechanical polishing is directly related to the facet hardness. Hence, the MRR of the (1 1‾ 05) facet is the slowest in that process, however, during CMP its MRR is 18 times faster than the Si-face, hints the different chemical and physical polishing mechanism. Accordingly, polishing recipes are proposed that can be adjusted to create atomically smooth wafers of arbitrary facets of SiC.

Quantitative probing of hydrogen environments in quasicrystals by high-resolution NMR spectroscopy

Metal-based quasicrystals with unique quasi-periodic atomic arrangements are known to store a large amount of hydrogen under reasonable pressure and temperature for practical application as energy storage materials. While details on the atomic environments around hydrogen are central to understanding their hydrogen-storage capacity, the experimental probing of hydrogen environments and direct estimation of hydrogen content in hydrogen-bearing metal compounds, including quasicrystals, remain the holy grail in metallurgy and materials science because of the lack of suitable spectroscopic probes of hydrogen in noncrystalline metal alloys. While 1H nuclear magnetic resonance (NMR) measurement under fast spinning has the potential to reveal the nature of bonding around hydrogen, applying NMR to these metallic compounds has been challenging. Here, we report the first 1H nuclear magnetic resonance (NMR) spectra of hydrogenated quasicrystals under fast sample spinning, revealing previously unknown details of the bonding environment and hydrogen content. The NMR spectra of TiZrNi quasicrystals show that the metal atoms in the first coordination shell of neutral hydrogen shift gradually from Zr to Ti to Ni with increasing hydrogen content. This trend accounts for Ni-induced increase in the hydrogen-storage capacity and the enhanced desorption kinetics observed near ambient conditions. The 1H peak maximum shifted linearly toward lower frequencies with increasing hydrogen content, highlighting the utility of fast-spinning NMR as a novel quantitative probe of hydrogenated quasicrystals. These results open a new window to access the nature of hydrogen and its content in diverse hydrogen-bearing energy materials based on metal alloys using high-resolution 1H NMR spectroscopy, providing improved prospects for the hydrogen economy.

Progress and Perspective of Metallic Glasses for Energy Conversion and Storage

AbstractOwing to its unique atomic arrangement and electronic structure, metallic glass (MG) has been widely investigated in the field of energy storage and conversion. In the past few decades, multiple strategies have been developed to synthesize bulk and nanosized MG based materials. Here, combining the structure–activity relationship of MG with electrochemical reaction kinetics, the substantial progress of glass structures in electrocatalytic processes are highlighted, including the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, methanol oxidation reaction, carbon dioxide reduction reaction, and nitrogen fixation. Meanwhile, applications of MG materials in energy storage devices, like supercapacitors and lithium‐ion batteries, are also introduced in detail. Finally, challenges and possibilities for reasonable design of highly‐efficient MG‐based electrode materials are proposed. The integration of high‐throughput methods, artificial intelligence technology, as well as advanced characterization techniques is fundamental to screen materials with remarkable performance. This review aims to deepen the understanding of the relationship between electronic structure and electrochemical performance, providing guidance for rational design of functional MG materials with outstanding activity, selectivity, and durability.

Solvent‐Assisted Synthesis of Supramolecular‐Assembled Graphitic Carbon Nitride for Visible Light Induced Hydrogen Evolution – A Review

AbstractMany graphitic carbon nitride (g‐C3N4)‐based photocatalysts have attracted a significant interest because of the unique arrangement of carbon and nitrogen atoms. Changeable morphologies with tunable bandgap of g‐C3N4 materials were used in many applications including batteries, photovoltaics, photocatalysts, sensors, etc. This review focuses on the recent progress in the solvent assisted supramolecular‐assembled carbon nitride preparation for visible light induced hydrogen evolution from water. The synthesis involves tailoring the supramolecular assembly from different monomers followed by calcination. Different types of non‐covalent interactions between the monomers have been explained. In addition, the crucial role of solvent has been re‐counted in terms of the alteration of the structural morphology of assemblies. The mechanistic pathways of interaction in the formation of supramolecular assemblies have been also documented by molecular dynamics simulation. Finally, visible light triggered hydrogen evolution has been demonstrated along with discussion on challenges and future research direction.

Unique Arrangement of Atoms Leads to Low Thermal Conductivity: A Comparative Study of Monolayer Mg2C.

Two-dimensional Mg2C, one of the typical representative MXene materials, is attracting lots of attention due to its outstanding properties. In this study, we find the thermal conductivity of monolayer Mg2C is more than 2 orders of magnitude lower than graphene and is even lower than MoS2 despite the relatively lighter atoms of Mg and C. Based on the comparative analysis with graphene, silicene, and MoS2, the underlying mechanism is found lying in the unique arrangement of atoms (lighter atoms in the middle plane) and large electronegativity difference in Mg2C. The phonon anharmonicity is strong due to the resonant bonding. In addition, dual band gaps emerge in the phonon dispersion of Mg2C, which limit the phonon-phonon scattering and reduce the phonon relaxation time. This study reveals a new mechanism responsible for low thermal conductivity, which would be helpful for designing thermal functional materials and pave the way for applications in thermoelectrics.

Synthesis of enhanced corrosion resistant Fe–B–C–Ti amorphous ribbons and evaluation of their photodegradation efficiency under light irradiation

Fe-based amorphous alloys have been found to be very efficient in the degradation of water pollutants due to their unique atomic arrangements with long-range disordered structure. In this work, Fe–B–C–Ti amorphous ribbons were successfully synthesized and showed high catalytic efficiency in the degradation of methylene blue (MB) under simulated sunlight and across a wide pH range. The catalytic efficiency was evaluated under different conditions to optimize the degradation performance. The amorphous ribbon Fe75B10C10Ti5 was found to exhibit the highest photocatalytic activity as explained by its optical and photoelectrochemical properties. It can degrade MB completely with low Fe-leaching and significant recyclability at pH close to a neutral range (pH 5). The degradation mechanisms can be explained in terms of photocatalytic activity along with the galvanic cell effect which contributed to the efficient MB degradation. This work provides a comprehensive idea for the synthesis of amorphous alloys by optimizing their elemental composition and also explains the catalytic activity of partially crystallized regions on the ribbon surface. The significant corrosion resistance and the quick degradation of MB in a wide pH range in a recyclable manner by these easily separable and highly efficient catalysts indicate great potential for their practical application.

Trimetallic synergy in dendritic intermetallic PtSnBi nanoalloys for promoting electrocatalytic alcohol oxidation

Developing effective and robust novel electrocatalysts for direct alcohol fuel cells has been gaining much attention. However, the widely used Pt catalyst suffers from limitations including the sluggish kinetics, severe CO poisoning, and catalyst lost caused by aggregation and Ostwald ripening during alcohol oxidation reaction. Herein, dendritic intermetallic PtSnBi nanoalloys were synthesized via a facile hydrothermal approach with high electrocatalytic performance and enhanced CO resistance for methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) owing to the synergism of the chosen three elements and unique three-dimensional morphology. Specifically, the PtSnBi nanoalloys display 4.6 and 6.7 times higher of mass activity (7.02 A mg−1Pt) and specific activity (16.65 mA cm−2) toward MOR than those of commercial Pt/C, respectively. The mass activity of PtSnBi nanoalloys still retains 75.7% of the initial value after 800 cycles of stability test, superior to Pt/C (38.0%). The dual-functional effect of Sn, optimized electronic structure by the ligand effect, and unique atomic arrangement are responsible for the enhanced MOR activity and stability of PtSnBi nanoalloys. Furthermore, the PtSnBi nanoalloys with highlighted anti-CO poisoning capacity also improve the electrocatalytic performance toward EOR, indicating their great promise as broad energy electrocatalysts.

Structural Uniqueness of the [Nb(As5)2]5- Cluster in the Zintl Phase Cs5NbAs10.

The structure of the novel Zintl phase, Cs5NbAs10, is reported for the first time. This compound crystallizes in the monoclinic P21/c space group (no. 14) with eight formula units per cell. The structure represents a unique atomic arrangement, constituting a new structure type with Wyckoff sequence e32. The most important structural element is the unprecedented [Nb(As5)2]5- cluster anion, formed by a Nb atom enclosed between two As5 rings. These nonaromatic cyclic species, formally [As5]5-, adopt an envelope conformation similar to that of cyclopentane. To date, it is only the second example of an [As5]5- ring with this conformation, reported in an inorganic solid-state compound. The bonding characteristics of the [Nb(As5)2]5- cluster and the [As5]5- rings are thoroughly investigated using first-principles methods and discussed. Electronic band structure calculations on Cs5NbAs10 suggest that this compound is a semiconductor with an estimated band gap of ca. 1.4 eV.

Novel class of nanostructured metallic glass films with superior and tunable mechanical properties

A novel class of nanostructured Zr50Cu50 (%at.) metallic glass films with superior and tunable mechanical properties is produced by pulsed laser deposition. The process can be controlled to synthetize a wide range of film microstructures including dense fully amorphous, amorphous embedded with nanocrystals and amorphous nano-granular. A unique dense self-assembled nano-laminated atomic arrangement characterized by alternating Cu-rich and Zr/O-rich nanolayers with different local chemical enrichment and amorphous or amorphous-crystalline composite nanostructure has been discovered, while significant in-plane clustering is reported for films synthetized at high deposition pressures. This unique nanoarchitecture is at the basis of superior mechanical properties including large hardness and elastic modulus up to 10 and 140 GPa, respectively and outstanding total elongation to failure (>9%), leading to excellent strength/ductility balance, which can be tuned by playing with the film architecture. These results pave the way to the synthesis of novel class of engineered nanostructured metallic glass films with high structural performances attractive for a number of applications in microelectronics and coating industry.

High Facets on Nanowrinkled Cu via Chemical Vapor Deposition Graphene Growth for Efficient CO2 Reduction into Ethanol

Achieving high electrochemical conversion of carbon dioxide (CO2) into valuable fuels and chemicals is one of the most promising directions to address environmental and energy challenges. Although several single-crystal based studies and simulation results have reported that rich in steps on Cu (100) surfaces are favorable to convert toward C2 alcohol products, most studies are still stuck in low-index (100) facets or surface defect-derived low density of step-sites. In the present work, we report the high production of ethanol by synthesizing a wrinkled Cu catalyst with high facets via a chemical vapor deposition (CVD) graphene growth process. Under our approach, we used graphene as a guiding material to produce wrinkled Cu film for use as an electrocatalyst. The graphene-grown Cu films are not only mass-producible but composed of a high density of step-sites with high-facet atomic arrangements, including the (200) and (310) facets, which are difficult to synthesize using existing methods. The wrinkled Cu film with a unique atomic arrangement showed high ethanol selectivity, achieving 40% faradaic efficiency (FE) at −0.9 V vs reversible hydrogen electrode (RHE), one of the largest selectivity values reported thus far for a Cu-based CO2 conversion catalyst. The C2 selectivity and productivity was 57% FE and −2.2 mA/cm2 at −1.1 V vs RHE, respectively. Density functional theory (DFT) calculation results demonstrated that such a high ethanol productivity is mainly attributable to the (310) facet of the wrinkles, which feature a low C–C coupling barrier (0.5 eV) and a preferred reaction path toward ethanol among other products.

Polaron transport in porous graphene nanoribbons

Porous graphene (PG) forms a class of graphene-related materials with nanoporous architectures. Their unique atomic arrangements present interconnected networks with high surface area and high pore volume. Some remarkable PG properties, such as high mechanical strength and good thermal stability, have been widely studied. However, their electrical conductivity, and most importantly, their charge transport mechanism are still not fully understood. Herein, we employed a numerical approach based on a 2D tight-binding model Hamiltonian to first reveal the nature of the charge transport mechanism in PG nanoribbons. Results showed that the charge transport in these materials is mediated by polarons. These carrier species are dynamically stable and present very shallow lattice distortions. The porosity allows for polaron-like charge carriers, and it can preserve the PG semiconducting character even in broader nanoribbons. The polarons move in PG within the optical regime with terminal velocities varying from 0.50 up to 1.15 Å/fs. These velocities are lower than those for polarons in conventional graphene nanoribbons (2.2–5.1 Å/fs).

Excellent electromagnetic wave absorption of Co/Fe2O3 composites by additional activated carbon for tuning the optical and the magnetic properties

The new absorbing materials, thin, light, and strong become a challenge and attract more scientists to find excellent absorption performance. In this work, the composite Co/Fe2O3/AC was achieved through a simple milling method at 10 Hz for 1 h. The Co/Fe2O3/AC for 20%AC has an excellent absorption of electromagnetic wave performance with a minimum reflection loss (RL) value of −69.39 dB for the thickness of 4 mm at the frequency 11.302 GHz, followed by 15% AC with an RL value of −61.74 dB for the thickness of 3 mm at the frequency 11.19 GHz. The excellent absorption performance is related to conductivity loss, multiple reflections, electron hoping, and scattering caused by the unique arrangement of atoms. The study provided new and high potentials composite for the development of electromagnetic wave absorbing materials.

Two-dimensional arsenene polymorph beyond the auxetic foam: high mechanical sensitivity and large, negative NPR

Single-layer δ-As and γ-P have unique atomic arrangement, which belong to the Pmc21 and Pbcm space groups, respectively. Because of the coupling hinge structure, the physical properties of the two materials have obvious anisotropy. In this paper, we report the mechanical properties of the single-layer δ-As and γ-P. That is, their inherent negative Poisson ratio (NPR) is -0.708 and -0.226, respectively. Surprisingly, the absolute value of the NPR of δ-As is approximately 26.2 times greater than that of single-layer black phosphorus (the NPR of single-layer black phosphorus is -0.027), and remains invariant at a certain strain range. Thus, single-layer δ-As will have huge potential applications in nanosensors and electronic wearable devices due to its invariant and large, negative NPR.

Pd(ii)-Based polyoxometalate polymers as highly efficient heterogeneous catalysts for Suzuki–Miyaura reactions

Five Pd(ii)/polyoxometalate catalysts with a unique atomic arrangement and high Pd loading were synthesized under solvothermal conditions, and their structures were determined by single crystal X-ray diffraction.

Atomically resolved tomographic reconstruction of nanoparticles from single projection: Influence of amorphous carbon support

Nanoparticles have a wide range of applications due to their unique geometry and arrangement of atoms. For a precise structure-property correlation, information regarding atomically resolved 3D structures of nanoparticles is utmost beneficial. Though modern aberration-corrected transmission electron microscopes can resolve atoms with the sub-angstrom resolution, an atomic-scale 3D reconstruction of a nanoparticle using Scanning Transmission Electron Microscopy (STEM) based tomographic method faces hurdles due to high electron irradiation damage and “missing-wedge”. Instead, inline 3D holography based tomographic reconstructions from single projection registered at low electron doses is more suitable for defining atomic positions at nanostructures. Nanoparticles are generally supported on amorphous carbon film for Transmission Electron Microscopy (TEM) experiments. However, neglecting the influence of carbon film on the tomographic reconstruction of the nanoparticle may lead to ambiguity. To address this issue, the effect of amorphous carbon support was quantitatively studied using simulations and experiments and it was revealed that increasing thickness and/or density of carbon support increases distortion in tomograms.