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]

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]

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]

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.)