Search

Alloying elements segregating to grain boundaries (GBs) is vital in determining structural stability and mechanical properties of alloys, especially in high‐entropy alloys (HEAs) that consist of multiple elements. However, some details remain unclear, such as the process of varied atoms (Cr and Co) cosegregation to GBs in FeNiCrCo alloy. Therefore, the competition and cooperation between Fe, Ni, Cr, and Co atoms segregating to GBs of FeNiCrCo alloy were investigated via molecular dynamic (MD) simulation. Five [110] symmetric tilt GBs of FeNiCrCo were applied to study the relation between the tendency of atomic segregation especially Cr and Co and GB characters including GB energy and GB excess free volume (GB excess volume). A competitive segregation phenomenon between Cr and Co atoms was discovered, which could be dominated by GB excess volume and different atomic radii among components. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) attract much attention as possible radiation-resistant materials due to their several unique properties. In this work, the generation and evolution of the radiation damage response of an FeNiCrCoCu HEA and bulk Ni in the early stages were explored using molecular dynamics (MD). The design, concerned with investigating the irradiation tolerance of the FeNiCrCoCu HEA, encompassed the following: (1) The FeNiCrCoCu HEA structure was obtained through a hybrid method that combined Monte Carlo (MC) and MD vs. the random distribution of atoms. (2) Displacement cascades caused by different primary knock-on atom (PKA) energy levels (500 to 5000 eV) of the FeNiCrCoCu HEA vs. bulk Ni were simulated. There was almost no element segregation in bulk FeNiCrCoCu obtained with the MD/MC method by analyzing the Warren–Cowley short-range order (SRO) parameters. In this case, the atom distribution was similar to the random structure that was selected as a substrate to conduct the damage cascade process. A mass of defects (interstitials and vacancies) was generated primarily by PKA departure. The number of adatoms grew, which slightly roughened the surface, and the defects were distributed deeper as the PKA energy increased for both pure Ni and the FeNiCrCoCu HEA. At the time of thermal spike, one fascinating phenomenon occurred where the number of Frenkel pairs for HEA was more than that for pure Ni. However, we obtained the opposite result, that fewer Frenkel pairs survived in the HEA than in pure Ni in the final state of the damage cascade. The number and size of defect clusters grew with increasing PKA energy levels for both materials. Defects were suppressed in the HEA; that is to say, defects were "cowards", behaving in an introverted manner according to the anthropomorphic rhetorical method. [ABSTRACT FROM AUTHOR]

Exploiting dual‐functional photoelectrodes to harvest and store solar energy is a challenging but efficient way for achieving renewable energy utilization. Herein, multi‐heterostructures consisting of N‐doped carbon coated MoS2 nanosheets supported by tubular TiO2 with photoelectric conversion and electronic transfer interfaces are designed. When a photo sodium ion battery (photo‐SIB) is assembled based on the heterostructures, its capacity increases to 399.3 mAh g−1 with a high photo‐conversion efficiency of 0.71 % switching from dark to visible light at 2.0 A g−1. Remarkably, the photo‐SIB can be recharged by light only, with a striking capacity of 231.4 mAh g−1. Experimental and theoretical results suggest that the proposed multi‐heterostructures can enhance charge transfer kinetics, maintain structural stability, and facilitate the separation of photo‐excited carriers. This work presents a new strategy to design dual‐functional photoelectrodes for efficient use of solar energy. [ABSTRACT FROM AUTHOR]

As a kind of efficient adsorptive material, hydrogel has a wide application prospect within different fields, owing to its unique 3D network structures composed of polymers. In this paper, different synthetic strategies, crosslinking methods and their corresponding limitations and outstanding contributions of applications in the fields of removing environmental pollutants are reviewed to further provide a prospective view of their applications in water resources sustainability. Furthermore, the applications within the biomedical field, especially in wound dressing, are also reviewed in this paper, mainly due to their unique water retention ability, antibacterial ability, and good biocompatibility. Finally, the development direction of hydrogels in the fields of environmental remediation and biomedicine were summarized and prospected. [ABSTRACT FROM AUTHOR]

Graphene is attracting much attention in condensed matter physics and material science in the two-dimensional(2D) system due to its special structure, and mechanical and electronic properties. However, the lack of electronic bandgap and uncontrollable phase structure greatly limit its application in semiconductors, such as power conversion devices, optoelectronic devices, transistors, etc. During the past few decades, 2D transition metal dichalcogenides (TMDs) with much more phase structures have attracted intensive research interest in fundamental studies and practical applications for energy storage, as catalysts, and in piezoelectricity, energy harvesting, electronics, optoelectronic, and spintronics. The controllable phase transition also provides another degree of freedom to pave the way for more novel devices. In this review, we introduce the abundant phase structures of 2D-TMDs, including 2H, 1T, 1T' and charge density waves, and highlight the corresponding attractive properties and applications of each phase. In addition, all the possible methods to trigger the phase transition in TMDs are systematically introduced, including strain engineering, electron doping, alloying, thermal, electric field, and chemical absorption. Finally, the outlook of future opportunities in TMD phase transitions and the corresponding challenges, including both the synthesis and applications, are also addressed. [ABSTRACT FROM AUTHOR]

Ceramics have become indispensable materials for a wide range of industrial applications due to their excellent properties. However, the traditional preparation of ceramic materials is often time-consuming and involves high sintering temperatures. These result in considerable energy consumption and high production costs, which limit the application of these materials in some industries. This paper focuses on the advent of polymer-derived ceramics (PDCs) technology, which enabled the application of ceramics to fibers, composites, coatings, and films, mainly due to the excellent design, process, and low-temperature ceramic properties. We review and evaluate the important research progress made in polymer-derived ceramics technology in recent years and discuss its recent development into high-entropy ceramics. The development of polymer-derived ceramics technology in the field of high-entropy ceramics has broad research prospects, which can greatly improve the understanding and design of high-entropy materials and accelerate their application in the industrial field. [ABSTRACT FROM AUTHOR]

MXene (Ti3C2Tx) film prepared by vacuum-assisted filtration (V-MXene film) is the most common 2D MXene macroscopic assembly with ultra-high electrical conductivity, tunable interlayer space, diverse surface chemical properties, favorable mechanical properties and so on, showing great commercial value in the fields of energy storage, electromagnetic interference shielding and actuators and so on. This paper focuses on the preparation, properties and applications of V-MXene film, objectively reviews and evaluates the important research progress of V-MXene film in recent years and analyzes the main problems at present. In addition, the development direction and trend of V-MXene film in the future are prospected from the aspects of preparation, property control and application fields, which provide guidance and inspiration for the further development of functional MXene-based films and make contributions to the progress of MXene technology. [ABSTRACT FROM AUTHOR]

The unique properties of MXenes that arise from terminating functional groups and oxidation of MXenes make them attractive for application in photovoltaic devices like perovskite solar cells (PSCs). Here, oxidation of Ti3C2Tx hydrocolloid was carried out to tune its properties desirable for an electron transport layer (ETL) in low-temperature processed PSCs. The calculations of the energy levels were carried out using the Vienna ab initio simulation package (VASP) code based on density functional theory (DFT). Oxidation of Ti3C2Tx can generate Ti–O bonds and effectively reduce the macroscopic defects of the film fabricated by spin-coating, while a transition from metallic material to semiconductor occurred after heavy oxidation. A better matching of energy levels between perovskite and ETL layer in the case of a hybrid of oxidized and pristine Ti3C2Tx renders a champion power conversion efficiency (PCE) of 18.29%. The improvement in PCE can be attributed to the increased electron mobility in the ETL, which promotes electron transport and reduces the electron–hole recombination. Hence, by presenting a simple method for high performance in PSCs by MXene-derived materials, this work demonstrates the great potential of these materials for applications in low-temperature processed PSCs and other photovoltaic technologies. [ABSTRACT FROM AUTHOR]

The ORR and OER properties of a series of recombinant single atom catalysts (SACs) prepared by recombining Pt single atoms on 26 representative MXenes were comprehensively studied by first-principles calculations. The stability of Pt atoms on the MXene surface was studied using formation energies and diffusion energy barriers. Charge transfer analysis showed that the Pt atoms not only acted as the catalytic center of the SACs but also behaved as a charge transfer medium between the MXene substrate and the reactants. The catalytic properties of the recombinant SACs were dependent on several interacting factors including the Pt-5d states, the work functions of the recombinant systems, the electronegativity of the submetals, and the vacant electron orbitals of the C/N and O/F elements of the MXenes. In all the recombinant SACs under investigation, V-, Ti-, Nb-, and Cr-based MXenes, including Ti2CF2-VF-Pt, Ti3C2F2-VF-Pt, V2CO2-VO-Pt, Nb2CF2-VF-Pt, Nb4C3F2-VF-Pt, Cr2TiC2F2-VF-Pt, Ti3(C,N)2-CO2-VO-Pt, and Ti3(C,N)2-NO2-VO-Pt, were screened as promising ORR catalysts. In particular, three F-terminated ones (Nb2CF2-VF-Pt, Nb4C3F2-VF-Pt, and Cr2TiC2F2-VF-Pt) were proposed as effective ORR/OER bifunctional catalysts. The results revealed the highly active nature of the selected SACs and highlighted the great potential of MXenes as efficient ORR and OER catalysts. [ABSTRACT FROM AUTHOR]

Lithium metal batteries are promising next generation energy storage devices. However, uncontrolled lithium dendrite growth and inevitable side reactions of traditional organic liquid electrolytes with electrodes are obstacles to their practical applications. Herein, a new ionogel electrolyte with an organic–inorganic semi-interpenetrating network is designed by the confinement of ionic liquid within a NH2 pendent group optimized cross-linked poly(ionic liquid) copolymer backbone and glass fiber scaffold. The ionogel electrolyte shows superior physicochemical properties, including improved lithium ion transmission, high mechanical strength, wide electrochemical window, non-leakage, non-volatility and fire resistance. In Li//Li symmetric cells fabricated with this ionogel electrolyte, repeated Li plating/stripping could last over 1800 h without significant dendrite formation. Besides, the full cells paired with a high-voltage Li3V2(PO4)3 cathode present excellent cycling stability with a capacity retention of 83% after 1000 cycles (0.5C rate, 3.0–4.3 V) and 91% after 100 cycles (0.2C rate, 3.0–4.8 V). This study presents a new strategy for the use of organic–inorganic semi-interpenetrating networks for designing new composite ionogel electrolytes with desirable properties for high-voltage LMBs. [ABSTRACT FROM AUTHOR]

Developing highly active, stable, and conductive bifunctional oxygen reduction (ORR) and oxygen evolution (OER) catalysts is a key step for fuel cells and metal–air batteries. Herein, an effective idea for designing bifunctional catalysts is presented by regulating the surface electronic structures of Nb2CT2 (T = O, F, and OH) using Pt/Pd single atoms. The results indicated that Pt-doped systems (Nb2CO2–VO–Pt, Nb2CF2–VF–Pt) were the most promising bifunctional ORR/OER catalysts. In particular, Nb2CF2–VF–Pt was even better than landmark Pt(111) and IrO2(110) catalysts, with relatively low overpotentials of 0.40 V and 0.37 V for ORR and OER, respectively. The high catalytic nature of Nb2CF2–VF–Pt was explained by electronic structures, volcano plots, and charge transfer mechanisms, which mainly depended on the electron donor capacity and synergistic effects from F-terminated groups and Pt noble metals. Moreover, 100% utilization of Pt was achieved for the designed bifunctional catalysts with a minimum radius between two adjacent active centers. This was the first design of a bifunctional ORR/OER catalyst based on Nb2CT2 and highlighted a new perspective on the application of MXenes. [ABSTRACT FROM AUTHOR]

The high electrochemical performance of Li2MnO3‐derived Li‐rich layered oxides suggests that Na2MnO3 might be a promising cathode material for sodium‐ion batteries for its effective anionic oxygen redox. However, experimental and theoretical evidence for anionic redox and enhanced Na+ capacity of Na2MnO3 has not been established. In the present work, the structural and thermal stability, and the anionic oxygen redox mechanism of Na2MnO3 were studied by using first‐principle calculations based on density functional theory. About 1.75 Na+ per formula unit were extracted from Na2‐xMnO3 through partial O2− oxidation while the local structure remained intact, resulting in a large theoretical capacity of 315 mA h g−1. Surface Na+ was extracted before bulk Na+, which might have led to oxygen loss and structural transformation from the surface to the material bulk. Given the importance of high capacity in practical applications, Na2MnO3 and its derived Na‐rich layered oxides might be considered promising cathode materials for sodium ion batteries. [ABSTRACT FROM AUTHOR]

The adsorption and activation of O2 is regarded as the first critical step for the oxygen reduction reaction (ORR), and catalysts with a high performance toward O2 adsorption and activation would provide a theoretical foundation for further investigations. Here, we have studied the adsorption and electronic properties as well as the catalytic activities of group 9–11 single metal atoms deposited on NbC(001), denoted M/NbC(001). According to the location of the d-band centers and the frontier molecular orbital analysis, single metals of Co, Rh, Ir and Ni on NbC(001) exhibit higher activities than other metals (Pd, Pt, Cu, Ag and Au). The quite different catalytic activities of M/NbC(001) may be attributed to the differences in their electro-negativities and work-functions. Meanwhile, the reasonable stabilities of Co, Rh, Ir and Ni on NbC(001) were clarified by investigating the agglomeration resistance and oxidation resistance, and the results indicate that Co and Ni have poor oxidative stability, and Rh and Ir are antioxidants on NbC(001). Further research into the adsorption and activation of O2 confirmed the outstanding properties of Rh/NbC(001) and Ir/NbC(001), which may provide great opportunities to find alternative catalysts. [ABSTRACT FROM AUTHOR]

The popularity of portable and wearable flexible electronic devices, coupled with the rapid advancements in military field, requires electromagnetic interference (EMI) shielding materials with lightweight, thin, and flexible characteristics, which are incomparable for traditional EMI shielding materials. The film materials can fulfill the above requirements, making them among the most promising EMI shielding materials for next‐generation electronic devices. Meticulously controlling structure of composite film materials while optimizing the electromagnetic parameters of the constructed components can effectively dissipate and transform electromagnetic wave energy. Herein, the review systematically outlines high‐performance EMI shielding composite films through structural design strategies, including homogeneous structure, layered structure, and porous structure. The attenuation mechanism of EMI shielding materials and the evaluation (Schelkunoff theory and calculation theory) of EMI shielding performance are introduced in detail. Moreover, the effect of structure attributes and electromagnetic properties of composite films on the EMI shielding performance is analyzed, while summarizing design criteria and elucidating the relevant EMI shielding mechanism. Finally, the future challenges and potential application prospects of EMI shielding composite films are prospected. This review provides crucial guidance for the construction of advanced EMI shielding films tailored for highly customized and personalized electronic devices in the future. [ABSTRACT FROM AUTHOR]

• The similarities and differences in the electrochemical behavior and mechanism of the bulk phase and monolayer in TiSe 2 were discussed. • Theoretical calculations illustrated that there are two stages of redox reaction in the lithiation process, both in bulk phase and monolayer TiSe 2. • Monolayer TiSe 2 was found to be a promising anode material for lithium-ion batteries with high theoretical capacity(780 mA·h·g−1 with a voltage window of 0.18–1.43 V) and fast diffusion kinetics (≤161 meV). Two-dimensional transition metal dichalcogenides (TMDs) have been intensively studied as electrode materials for lithium-ion batteries. But, most of TMDs are low electronic conductors, and there is lack of research on the distinct electrochemical mechanisms of monolayer and bulk TMDs. In this work, the Li+ storage properties of monolayer and bulk TiSe 2 are studied by first-principles calculations based on the density functional theory. Calculations showed that bulk TiSe 2 works on the intercalation mechanism, which results in a theoretical capacity of 260 mA·h·g−1 in the voltage window of 1.14–2.09 V. In comparison, monolayer TiSe 2 works on the adsorption mechanism which gives a theoretical capacity of 780 mA·h·g−1 in 0.18–1.43 V. A two-stage redox process was revealed for both TiSe 2 forms. In the initial stage, Se acted as the main redox species; then both Ti and Se participated in the redox reaction. In addition, the material possesses low Li+ diffusion barriers. Especially, a very small diffusion barrier of 163 meV at high Li+ concentration and 39 meV at low Li+ concentration was obtained for monolayer TiSe 2 , which provide great potential as a high rate anode material for lithium ion batteries. [ABSTRACT FROM AUTHOR]

Out-of-plane pressure and electron doping can affect interlayer interactions in van der Waals materials, modifying their crystal structure and physical and chemical properties. In this study, we used magnetic monolayer 1T/1T'-CrS 2 and high symmetry 2D-honeycomb material GeC to construct a GeC/CrS 2 /GeC triple layered van der Waals heterostructure (vdWH). Based on density functional theory calculations, we found that applying out-of-plane strain and doping with electrons could induce a 1T'-to-1T phase transition and consequently the ferromagnetic (FM)-to-antiferromagnetic (AFM) transition in the CrS 2 layer. Such a phase and magnetic transition arises from the pressure and electron-induced interlayer interaction enhancement. The electron doping can effectively decrease the critical compressive stress from ∼4.3 GPa (charge neutrality) to ∼664 MPa ( Q = 9 × 10 -3 e - per atom) for the FM-to-AFM transition. These properties could be used to fabricate and program the 2D lateral FM/AFM heterostructures for artificial controlled spin texture and miniaturized spintronic devices.

Exploiting dual-functional photoelectrodes to harvest and store solar energy is a challenging but efficient way for achieving renewable energy utilization. Herein, multi-heterostructures consisting of N-doped carbon coated MoS 2 nanosheets supported by tubular TiO 2 with photoelectric conversion and electronic transfer interfaces are designed. When a photo sodium ion battery (photo-SIB) is assembled based on the heterostructures, its capacity increases to 399.3 mAh g -1 with a high photo-conversion efficiency of 0.71 % switching from dark to visible light at 2.0 A g -1 . Remarkably, the photo-SIB can be recharged by light only, with a striking capacity of 231.4 mAh g -1 . Experimental and theoretical results suggest that the proposed multi-heterostructures can enhance charge transfer kinetics, maintain structural stability, and facilitate the separation of photo-excited carriers. This work presents a new strategy to design dual-functional photoelectrodes for efficient use of solar energy., (© 2023 Wiley-VCH Verlag GmbH.)

As a kind of efficient adsorptive material, hydrogel has a wide application prospect within different fields, owing to its unique 3D network structures composed of polymers. In this paper, different synthetic strategies, crosslinking methods and their corresponding limitations and outstanding contributions of applications in the fields of removing environmental pollutants are reviewed to further provide a prospective view of their applications in water resources sustainability. Furthermore, the applications within the biomedical field, especially in wound dressing, are also reviewed in this paper, mainly due to their unique water retention ability, antibacterial ability, and good biocompatibility. Finally, the development direction of hydrogels in the fields of environmental remediation and biomedicine were summarized and prospected.

Redox mediators (RMs) have a substantial ability to govern oxygen reduction reaction (ORR) in Li-O 2 batteries, which can realize large capacity and high-rate capability. However, studies on understanding RM-assisted ORR mechanisms are still in their infancy. Herein, a quinone-based molecule, vitamin K1 (VK1), is first used as the ORR RM for Li-O 2 batteries, together with 2,5-di- tert -butyl-1,4-benzoquinone (DBBQ), to elucidate key factors on the catalytic activity of RMs. By combining experiments and first-principle computations, we demonstrate that the reduced VK1 has strong oxygen affinity and can effectively retard the deposition of Li 2 O 2 films on the electrode surface, thereby guaranteeing enough active sites for electron transfer. Besides, the low reaction free energy of disproportionation of the Li(VK1)O 2 intermediate into Li 2 O 2 also significantly accelerates the ORR process. Consequently, the catalytic activity of VK1 is significantly boosted, and the discharge capacity of VK1-assisted batteries is 3.2-4.5 times that of DBBQ-assisted batteries. This study provides new insight for better understanding the working roles of RMs in Li-O 2 batteries.

Structure determines properties, and properties determine applications, which is an important ideology of natural sciences. For optical materials, it is vital to lucubrate the corresponding relationship between the local crystal structure and luminescence properties for their design, synthesis, and application. This work reports a newly designed Y 2 Mg 2 Al 2 Si 2 O 12 (YMAS):Eu 3+ red phosphor, in which difunctional Eu 3+ ion is used as a red-light activator and spectroscopic probe. The qualitative and quantitative studies on the relationship between the local crystal structure and the luminescence properties of YMAS:Eu 3+ are performed experimentally and computationally, using the Y 3 Al 5 O 12 (YAG):Eu 3+ as contrast. Moreover, compared with YAG:Eu 3+ , the newly designed YMAS:Eu 3+ has stronger luminescence, superior Commission Internationale de L'Eclairage chromaticity coordinates, a lower optimal doping concentration, and equally excellent thermal stability. The satisfactory color-rendering index of packaged white-light-emitting diodes demonstrates its potential performance as a red phosphor. Briefly, this work provides not only a new case for the study of the local crystal structure and luminescence properties but also a new possibility for the application of a red phosphor in solid-state lighting.

Multiple negative factors, including the poor electronic conductivity of sulfur, dissolution and shuttling of lithium polysulfides (Li 2 S n ), and sluggish decomposition of solid Li 2 S, seriously hinder practical applications of lithium-sulfur (Li-S) batteries. To solve these problems, a general strategy was proposed for enhancing the electrochemical performance of Li-S batteries using surface-functionalized Ti 3 C 2 MXenes. Functionalized Ti 3 C 2 T 2 (T = N, O, F, S, and Cl) showed metallic conductivity, as bare Ti 3 C 2 . Among all Ti 3 C 2 T 2 investigated, Ti 3 C 2 S 2 , Ti 3 C 2 O 2 , and Ti 3 C 2 N 2 offered moderate adsorption strength, which effectively suppressed Li 2 S n dissolution and shuttling. This Ti 3 C 2 T 2 exhibited effective electrocatalytic ability for Li 2 S decomposition. The Li 2 S decomposition barrier was significantly decreased from 3.390 eV to ∼0.4 eV using Ti 3 C 2 S 2 and Ti 3 C 2 O 2 , with fast Li + diffusivity. Based on these results, O- and S-terminated Ti 3 C 2 were suggested as promising host materials for S cathodes. In addition, appropriate functional group vacancies could further promote anchoring and catalytic abilities of Ti 3 C 2 T 2 to boost the electrochemical performance of Li-S batteries. Moreover, the advantages of a Ti 3 C 2 T 2 host material could be well retained even at high S loading, suggesting the potential of surface-modified MXene for confining sulfur in Li-S battery cathodes.

Transition metal polysulfides with high S content, such as VS 4 , TiS 4 , and MoS 3 , have high specific Li + capacities, but their reaction mechanisms for lithium-ion batteries remain unclear due to unknown intermediate products. In this work, first-principles calculations based on the density functional theory were performed to reveal the electrochemical properties of VS 4 for lithium-ion batteries. The results demonstrated multiple phase transformations during Li + insertion, starting with nucleation transformation from VS 4 to Li 3 VS 4 and followed by gradual decomposition reactions. Enthalpy-driven long-range migration of Li 2 S molecules resulted in crystalline to amorphous transformation during decomposition. S and V successively behaved as redox centers for Li x VS 4 before and after x = 3. Moreover, low activation energy and high Li + diffusivity were observed at room temperature, revealing superior rate capability of the material.