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In recent times, newly unveiled 2D materials exhibiting exceptional characteristics, such as MBenes and MXenes, have gained widespread application across diverse domains, encompassing electronic devices, catalysis, energy storage, sensors, and various others. Nonetheless, numerous technical bottlenecks persist in the development of high‐performance, structurally flexible, and adjustable electronic device materials. Research investigations have demonstrated that 2D van der Waals superlattices (vdW SLs) structures comprising materials exhibit exceptional electrical, mechanical, and optical properties. In this work, the advantages of both materials are combined and compose the vdW SLs structure of MBenes and MXenes, thus obtaining materials with excellent electronic properties. Furthermore, it integrates machine learning (ML) with first‐principles methods to forecast the electrical properties of MBene/MXene superlattice materials. Initially, various configurations of MBene/MXene superlattice materials are explored, revealing that distinct stacking methods exert significant influence on the electronic structure of MBene/MXene materials. Specifically, the BABA‐type stacking of CrB (layer A) and Co2CO2 MXene (layer B) is most stable configureation. Subsequently, multiple descriptors of the structure are constructed to predict the density of states of vdW SLs through the employment of ML techniques. The best model achieves a mean absolute error (MAE) as low as 0.147 eV. [ABSTRACT FROM AUTHOR]

Gradient nanostructured metals have become one of the research hotspots in the field of materials science due to their excellent mechanical properties and unique deformation behavior. In our contributions, the nanotwin gradient was introduced into the nanocrystalline Ni–Co alloy, and the influence of the gradient structure on the shear properties and microscopic deformation behavior was studied in order to reveal the strengthening mechanism. The gradient nanotwin Ni–Co alloy has elastic deformation and work hardening at the initial shear stage. The stress decreases after reaching the stress limit, and the uniform plastic deformation is maintained at the later stage. The excellent stability of fine twin layer and its effective hindrance to dislocation nucleation and movement can improve the strength of the material. In addition, the yield and work hardening of nanotwin gradient Ni–Co alloy are easy to occur at low temperature, and the stress–strain curve fluctuates obviously. At high temperature, the alloy is prone to plastic deformation, and the strength is reduced macroscopically. The higher the temperature is, the more difficult it is to yield. The results provide a solid theoretical basis for the design of Ni‐based alloys. [ABSTRACT FROM AUTHOR]

Grain boundary engineering is an effective and feasible metal strengthening strategy to enhance the properties of nanopolycrystalline alloys by changing the number, configuration, and connectivity of different types of grain boundaries, especially for the twin boundaries. In the present contribution, the effect of twin spacing and loading mode on the deformation behavior and mechanism of NiCoAl columnar polycrystalline alloy is investigated. The results show that the nanotwins can not only increase the bearing capacity of dislocations but also emit many dislocations, resulting in the coupling effect of dislocation strengthening and twin strengthening. When the twin spacing is large, intrinsic stacking faults occur and gradually transform into deformation twins. In this stage, Shockley partial dislocation controls plastic deformation. When the twin spacing is small, the high‐density twin layers and stacking faults are more likely to interweave, showing a combination action of Shockley partial dislocation and stair‐rod dislocation. With the loading changing to Z axis, the yield strength decreases due to reduced resistance to the dislocation and a weakened number of Shockley partial dislocations of the emission, leading to less strengthening of the twins. The insights provide a solid theoretical foundation for the further application of NiCoAl in industrial production. [ABSTRACT FROM AUTHOR]

The addition of oxygen atoms in solid solution to α‐Ti alloy can increase not only its hardness but also its brittleness. Herein, the edge dislocation mobility of Ti–O single crystals at oxygen concentrations of 0–2 at% and temperatures of 100–900 K is investigated by molecular dynamics simulations. The results show that the interstitial oxygen atoms have a strong hindering effect on the a/3 [112¯0] edge dislocations on the {1¯100} prismatic planes, which is attributed to the pinning effect of the vacancy clusters on the dislocation movement due to the interstitial oxygen atoms, thus leading to pronounced dislocation strengthening and hardening. The critical resolved shear stress (CRSS) for dislocation movement increases with increasing oxygen content and decreases with increasing temperature. Moreover, the effect of oxygen concentration on dislocation mobility also diminishes with increasing temperature. [ABSTRACT FROM AUTHOR]

Herein, the effects of different Co content and temperature factors on the shear mechanical properties of nano‐polycrystalline nickel–cobalt alloy are analyzed by molecular dynamics (MD) simulations. It is found in the work that the highest shear modulus of 63.03 GPa is obtained when the Co content is 10%, attributed to the lattice distortion caused by the difference in the lattice parameters between two elements. During the shearing process, the multilevel twins are present with intensification of the deformation process, resulting in excellent dynamic shear performance. Shockley dislocations will drive the stacking faults and other partial dislocations to constitute a tetrahedral edge, and finally forms a tetrahedral structure. In addition, as the temperature of the shear environment increases, the highest strain and stress decrease. The grain boundary atoms increase significantly, and the atoms inside the grains decrease accordingly. As the degree of atomic disorder increases, the grain boundaries will melt gradually. The decrease of partial dislocation density can weaken the entanglement effect caused by dislocations. The previous conclusions promote the product development and application of nano‐polycrystalline alloys in the future, and provide important guidance significant for the engineering application of nickel–cobalt alloys. [ABSTRACT FROM AUTHOR]

The fabrication of Zn‐CO2 batteries is a promising technique for CO2 fixation and energy storage. Herein, nitrogen‐doped ordered mesoporous carbon (NOMC) is adopted as a bifunctional metal‐free electrocatalyst for CO2 reduction and oxygen evolution reaction in the near‐neutral electrolyte. The ordered mesoporous structures and abundant N‐dopings of NOMC facilitate the accessibility and utilization of the active sites, which endow NOMC with excellent electrocatalysis performance and outstanding stability. Especially, a nearly 100% CO Faradaic efficiency is achieved at an ultralow overpotential of 360 mV for CO2 reduction. When constructed as an aqueous rechargeable Zn‐CO2 battery using NOMC as the cathode, it yields a high peak power density of 0.71 mW cm−2, a good cyclability of 300 cycles, and excellent energy efficiency of 52.8% at 1.0 mA cm−2. [ABSTRACT FROM AUTHOR]

Using hydrazine oxidation reaction (HzOR) to replace the oxygen evolution reaction is an effective way to decrease the overpotential of the anodic reaction in overall water splitting (OWS), facilitating cost‐effective and safe hydrogen production. Herein, Rh2S3/N‐doped carbon hybrids (Rh2S3/NC) are first reported as novel and efficient bifunctional electrocatalysts for hydrazine‐assisted hydrogen generation over a wide pH range. Specifically, Rh2S3/NC exhibits low overpotentials for the hydrogen evolution reaction (HER) in alkaline (38 mV), neutral (46 mV), and acidic (21 mV) electrolytes, to reach the current density of 10 mA cm−2, and maintains the activities over 70 h. Meanwhile, Rh2S3/NC also displays competitive HzOR performance at all‐pH electrolytes. Thus, serving as a bifunctional electrocatalyst for both HER and HzOR, Rh2S3/NC shows overwhelming‐Pt/C performance in three electrolytes, and can save over 93.3%, 85.2%, and 78.3% energy consumption compared to the corresponding OWS system. Moreover, theoretical calculations confirm that Rh2S3/NC owns low free‐energy changes of the H adsorption and the dehydrogenation of adsorbed NHNH both of which are beneficial to enhance catalytic activity. This work develops a novel bifunctional electrocatalyst with free pH‐dependent condition for the hydrazine‐assisted electrolysis system to furtherly reduce the cost of massive industrial H2 production. [ABSTRACT FROM AUTHOR]

Solar‐driven electrochemical overall CO2 splitting (OCO2S) offers a promising route to store sustainable energy; however, its extensive implementation is hindered by the sluggish kinetics of two key reactions (i.e., CO2 reduction reaction and oxygen evolution reaction (CO2RR and OER, respectively)). Here, as dual‐functional catalysts, Co2FeO4 nanosheet arrays having high electrocatalytic activities toward CO2RR and OER are developed. When the catalyst is applied to a complete OCO2S system driven by a triple junction GaInP2/GaAs/Ge photovoltaic cell, it shows a high photocurrent density of ≈13.1 mA cm−2, corresponding to a remarkably high solar‐to‐CO efficiency of 15.5%. Density functional theory studies suggest that the Co sites in Co2FeO4 are favorable to the formation of *COOH and *O intermediates and thus account for its efficient bifunctional activities. The results will facilitate future studies for designing highly effective electrocatalysts and devices for OCO2S. [ABSTRACT FROM AUTHOR]

Powered by renewable electricity, the electrochemical reduction of nitrogen to ammonia is proposed as a promising alternative to the energy‐ and capital‐intensive Haber–Bosch process, and has thus attracted much attention from the scientific community. However, this process suffers from low NH3 yields and Faradaic efficiency. The development of more effective electrocatalysts is of vital importance for the practical applications of this reaction. Of the reported catalysts, single‐atom catalysts (SACs) show the significant advantages of efficient atom utilization and unsaturated coordination configurations, which offer great scope for optimizing their catalytic performance. Herein, progress in state‐of‐the‐art SACs applied in the electrocatalytic N2 reduction reaction (NRR) is discussed, and the main advantages and challenges for developing more efficient electrocatalysts are also highlighted. [ABSTRACT FROM AUTHOR]

Based on first‐principles with the generalized gradient approximation (GGA) of the Perdew–Burke–Ernzerhof (PBE) form, the authors carry out systematic investigations regarding the electronic structures and optical properties of zinc‐blende (ZB) ZnS doped with six types of transition metals. The Cd‐doped system has greater structural stability with a lower formation energy of 0.526 eV compared to other systems. Additionally, the band structures of systems are employed to show the superior semiconductor capacity of Mo‐ and Pt‐doped systems with decreased band gaps (EG) of 0.978 eV and 0.843 eV, which are smaller than those of the pure system and others. Moreover, charge difference density maps show that the covalent properties of MoS and PtS bonds are enhanced by exposing the electron‐deficient region. Meantime, optical properties, including absorption and reflectivity spectra, dielectric constant, and loss function, are introduced to reveal that the absorption spectra curves reach the lowest absorption peak of 2.375 × 105 cm−1 at 7.227 eV for the Mo‐doped system, in which the system exhibits a relatively negative reflectivity spectrum and dielectric loss that is expected in the solar cell industry, predicting its broad scope of application prospects in the photoelectric and microelectronic device fields. [ABSTRACT FROM AUTHOR]

Mechanical behavior and plastic deformation mechanism of a new type of Co30Fe16.67Ni36.67Ti16.67 high entropy alloys (HEAs) have been calculated by the molecular dynamics method. The results show that the polycrystalline Co30Fe16.67Ni36.67Ti16.67 HEA has remarkable tensile plasticity and anisotropy. When the crystallographic orientation of the grain is <001>, the plastic deformation mechanism is face‐centered cubic (FCC)→body‐centered cubic (BCC) transformation and deformation twins. Grain boundary and vacancy reduce the nucleation energy of FCC→BCC phase transition, making BCC phase nucleation easy and growing in a shear manner, eventually forming deformation twins in the BCC phase. When the crystallographic orientation of grain is <110> and <111>, the plastic deformation mechanism is stacking faults, FCC→hexagonal‐close‐packed (HCP) phase transformation, and deformation twins. The motion of Shockley dislocation leads to the stacking fault, intrinsic stacking fault leads to the FCC→HCP phase transition, extrinsic stratification fault leads to the twin deformation, and the grain refining occurs during the tension process. Temperature and strain rate also have strong effects on tensile strength and elastic modulus. These results will provide a theoretical basis for the development of the HEAs and expand their application. [ABSTRACT FROM AUTHOR]

Potassium (K) metal anodes are the most competitive candidates for low‐cost and high‐energy density rechargeable batteries. However, uncontrolled K dendrite growth strictly impedes the practical application of K metal anodes. Herein, a potassiophilic and conductive dual‐gradient free‐standing host (named TS‐PKS) composed of the bottom layer with Ti3CN and F doped SnO2 (F‐SnO2) and the top layer with perfluorinated sulfonic acid K (PFSA‐K) and ordered mesoporous silica (SBA15) is constructed to achieve dendrite‐free K deposition. The potassiophilicity and conductivity of the TS‐PKS host increase along with the depth direction to generate a bottom‐up dual‐gradient of K+ affinity and electroconductivity. Such bottom‐up dual‐gradient of K+ affinity and electroconductivity can synergistically manipulate uniform K metal deposition following the bottom‐up manner, preventing the notorious K dendrite growth. As a result, the TS‐PKS@K symmetric cell can stably cycle over 2800 h at 0.5 mA cm−2/0.5 mAh cm−2. Meanwhile, the TS‐PKS@K//PTCDA full battery also exhibits an initial specific capacity of 118.3 mAh g−1 at a high current density of 500 mA g−1 and maintains up to 81.1 mAh g−1 after 1000 cycles. This novel dual‐gradient strategy design offers a straightforward approach to effectively manipulate K metal deposition manner for achieving dendrite‐free K metal anodes. [ABSTRACT FROM AUTHOR]

Front Cover: Single-Atom Catalysts for the Electrocatalytic Reduction of Nitrogen to Ammonia under Ambient Conditions (Chem. B Benefits of being single b : Single-atom catalysts (SACs) have attracted much attention in the design of high-performance N SB 2 sb reduction reaction (NRR) electrocatalysts owing to their significant advantages of efficient atom utilization and unsaturated coordination configurations. In the Minireview by Xijun Liu et al., state-of-the-art SACs applied in the electrocatalytic NRR are discussed, and the main advantages and challenges for developing more efficient electrocatalysts are highlighted. [Extracted from the article]