Two-dimensional transition metal carbides (MXenes) possess inherent advantages, including diverse chemical compositions, tunable layer thicknesses, and facile surface functionalization. These properties make them suitable as promising low-cost, stable and highly active non-precious metal catalysts for hydrogen evolution reaction (HER). However, the complexity of its structure and the lack of descriptors impede the rational design of highperformance HER electrocatalysts. In this work, employing a series of oxygen-terminated double-transition-metal carbides (M ' 2M '' C2O2, where M ' = Ti, V, Cr; M '' = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W), we propose the reasonable regulation strategy for the improved HER performances of MXene by integrating multidimensional insights from stacking energy, thermodynamic stability, electronic properties and activity descriptors. It is illustrated that ABA stacking configurations with high electron density commonly exhibit the enhanced thermodynamic stability. Six M ' 2M '' C2O2 are screened out exhibiting superior HER activity and robust thermodynamic stability across a wide hydrogen coverage. According to Gradient-Boosted Regression (GBR), the surface O p-band center (epsilon p) is identified as a robust activity descriptor for M ' 2M '' C2O2, which can even be extended to defect-containing model (R2 = 0.74). Furthermore, we demonstrate a rational design strategy for MXenes with improved HER performance through appropriately modulating epsilon p via introducing oxygen vacancies.

Two-dimensional (2D) iron trihalides (FeX3, X = F, Cl, Br, I) are an emerging family of van der Waals magnets whose fundamental physical properties are not yet fully understood. In this work, we present a systematic first-principles study incorporating hybrid functional (HSE06) calculations and Hubbard U corrections to unravel the spin state, magnetic order, electronic structure, and doping response in monolayer FeX3. The high-spin (S = 5/2) state is unequivocally established as the universal local ground state across the series. A chemical tuned magnetic transition is identified: FeF3 adopts Neel-type antiferromagnetic (AFM) order, while FeCl3, FeBr3, and FeI3 are ferromagnetic (FM) semiconductors with Curie temperatures (T-C) monotonically increasing from 154 K to 238 K. This trend is driven by the competition between direct AFM exchange and halogen-mediated FM superexchange. Electronically, FeCl3 and FeBr3 are identified as bipolar magnetic semiconductors, exhibiting a perfect linear scaling of the band gap with halogen electronegativity. An effective tight-binding model derived from maximally Wannier functions reveals a progressive increase in crystal-field splitting (Delta(oct)) from 3.36 eV to 4.22 eV, underpinning the evolving orbital hierarchy across iron trihalides. Crucially, electron doping induces a nonmonotonic magnetic evolution, from FM to geometrically frustrated AFM (zigzag/stripy), culminating in a reentrant FM state, driven by the competition between kinetic energy minimization and orbital-selective electron correlations. Finally, bilayer systems exhibit a universally robust interlayer AFM coupling driven by p(z) orbital-mediated superexchange across the van der Waals gap. Our work provides a complete microscopic picture of the basic magnetic and electronic properties of the 2D FeX3, establishing them as a highly versatile material platform for tunable magnetism and spintronics.

Surface coking under high temperature degrades the performance and longevity of engine components. Understanding its mechanism is essential for developing effective mitigation strategies. This study integrates density functional theory (DFT), ab initio molecular dynamics (AIMD), and targeted experimental characterizations to uncover the coking mechanism on stainless steel and explain the anti-coking behavior of an ALD-fabricated TiO2 coating. Simulations reveal that Fe/Ni sites on bare steel catalyze the initial cracking of long-chain alkanes (n-decane) into reactive species, which strongly chemisorb through pronounced hybridization between C-p and metal-d orbitals. Conversely, a stable TiO2 coating alters the interfacial chemistry: lowering the adsorption energy of coke precursors by >40% and suppressing accumulation. Crucially, AIMD simulations reveal a surface-oxygen-mediated carbon-removal pathway, in which adsorbed carbon reacts with surface lattice oxygen and desorbs as CO at 700-900 K, underpinning the active carbon desorption behavior of the TiO2 coating. TPSR measurements confirm this mechanism by showing distinct CO desorption peaks between 379 and 800 degrees C. Furthermore, combustion tests demonstrate that the ALD-fabricated TiO2 coating reduces carbon deposition by similar to 75%. Overall, this work providing a theoretical foundation for the rational design of advanced anti-coking coatings.

The dehydrogenation on group IV elements Si, Ge, or Sn doped MgH2(110) surface was investigated by first-principles calculations. In addition, the dopant site preference was determined by comparing the total energies of different doping site systems. The results showed that Si and Ge prefer to occupy interstitial sites, while Sn prefers to replace one Mg atom. The electronic structure and density of states show that the doping of Si, Ge, or Sn significantly weakens the Mg-H bond on the surface of MgH2(110), and the band gap of the system is reduced, leading to structural instability. Finally, the calculated results of dehydrogenation energy and activation energy barrier indicated that Ge best improves the thermodynamics and hydrogen desorption kinetics of the MgH2(110) surface, followed by Si and Sn.

Developing efficient non-precious metal catalysts for high-current-density hydrogen evolution reaction (HER) is crucial for water splitting. This work fabricates a hierarchical heterostructured hydrogen electrode on nickel foam (Co–P@MoO2-x@NF), which integrates a MoO2-x support layer with a Co–P active layer, demonstrating outstanding HER performance with an overpotential of 170.5 mV at 500 mA cm−2 and stable operation for 1000 h at 100 mA cm−2 in 1 M KOH. The efficient hydrogen spillover effect facilitated by the built-in electric field (BIEF) in the MoO2-x/Co–P interface, coupled with the synergistic modulation of the Co-3d and Mo-4d band centers, which collectively optimize the thermody-namics and kinetics of H2O adsorption and dissociation. In situ formation of Co2P2O7 nano-sheets form in situ on the electrode surface, further enhancing its hydrophilicity, mass transfer, and structural stability. This study offers a new design strategy for durable, high-performance HER catalysts.

Ga2O3/GaN hybrid ultraviolet (UV) photodetector (PD) has photon-carriers generated in the Ga2O3 region and transported in the GaN layer. In this work, by designing Ga2O3/GaN UV PD with a gate metal on the Ga2O3 surface, common-connected with the cathode on the GaN layer, we have revealed that the impact of substrate defects in the GaN region on the photo-generated carrier transport is significant for Ga2O3/GaN UV PD. As a result, we have observed asymmetric current in terms of the anode bias of different polarities. According to our measurement, the photocurrent of 8.81 × 10-5 A/cm2/2.34 × 10-5 A/cm2, the responsivity of 6.65 A/W/1.16 A/W, the rise time of 1.07 s/1.14 s, and the fall time of 1.16 s/1.35 s are achieved at the anode bias of -6 V/+6 V, respectively. When the anode is biased positively, the poorer performances are well attributed to the substrate defects, such that Ga2O3/GaN UV PD pushes the photo-generated carriers deep into the more defected GaN substrate region. This observation is further proven by the developed physical models.

The stability and mechanical properties of CuFe alloys are primarily dependent on the Fe alloying induced solid solution/segregation, which can modulate the local atomic structure of grain boundaries (GBs), and thus their motion. Herein, hybrid Monte Carlo and Molecular dynamics (MC/MD) simulations are performed to investigate the effects of random Fe solute atoms and segregated Fe clusters on the atomic configurations and shearing driven motion of <110> tilt GBs in CuFe alloy. It is found that Fe clusters with FCC structure tend to segregate into dissociated and undissociated GBs except twin boundaries (TBs), markedly influencing the local structure and strain distribution of GBs. Different shear deformation mechanisms and GB motion behaviors are evidenced, and GB migration is coupled with shear deformation, dislocation emission and stacking fault (SFs) extension from GB. Thermodynamically, both the random Fe solute atoms and Fe clusters could lower the energy barrier of dislocation nucleation, reaction and gliding from GBs, however, kinetically, they will also pin and drag dislocation gliding and SFs extension. The balancing between the thermodynamical and kinetical determine the GB motion behaviors. The results may contribute to the coupling design of alloying and GB engineering in nano-crystalline alloys.

Lithium-sulfur (Li-S) batteries have attracted significant attention due to their high energy density and low cost of raw materials. Although the SPAN cathode has better electrochemical performance than the traditional S8/C composite, it is far from meeting the needs of commercialization, and its energy density, cycle stability, and rate performance need to be further improved. In this study, the swelling and dispersion of SPAN in different solvents are investigated for the first time by using different binders to optimize the electrode structure. The selection of water as a solvent can reduce the swelling of SPAN and inhibit cracking in the electrode preparation process, which effectively improves the structural stability of the electrode during the long-time charging and discharging process. The combination of CMC&SBR binder can reduce the agglomeration of active material and conductive carbon and contribute to the capacity of SPAN at a high current rate. As a result, the non-swelling SPAN with CMC&SBR binder exhibits a stable long cycling performance (83% capacity retention for 200 cycles at 1 C) and high rate performance (1192 mAh g-1 at 5 C). In particular, the Li-S pouch cell is able to cycle stably for more than 50 cycles at 0.2 C under high loading (SPAN loading level of 7.2 mg cm-2 and area capacity over 4 mAh cm-2) with the specific capacity maintained at 1306 mAh g-1. This work has the potential to promote the commercialization of Li-SPAN batteries.

ABSTRACT Motion recognition and image preprocessing are critical for artificial vision systems, but there remains a need for more efficient and energy‐saving devices with versatile image processing capabilities. Herein, we developed highly efficient photovoltaic detectors with bidirectional photocurrent and polarization‐sensitive characteristics by sandwiching gold nanoparticles (Au NPs) between MoTe 2 and ReS 2 , enabling two photoelectric units to operate collaboratively. The Au NPs induce localized surface plasmon resonance (LSPR) and hot electron injection, modulating the interface electronic structure, enhancing the light absorption efficiency, and extending the spectral response range to 1550 nm, surpassing the bandgap limitations of MoTe 2 and ReS 2 . The responsivity and detectivity reach up to 8.35 A W −1 and 9.6 × 10 11 Jones under 808 nm, respectively, which are about two orders of magnitude improvement over the pristine MoTe 2 /ReS 2 device. The polarization ratio (PR) also increases from 4.7 to 9.1, which enables multi‐task image processing applications. Leveraging the bidirectional photocurrent and polarization photo‐response, the convolution processing is further combined with the device for realizing motion recognition and image processing tasks, including sharpening, edge extraction, and noise filtering. This work opens a new avenue for the development of Au NPs engineered photodetectors for image processing and motion recognition applications.

The structural, electronic, and magnetic properties of one-dimensional (1D) MoX3 (X = Br,I) atomic chains (ACs), as well as their sensitivity to strain, carrier doping, and optical excitation, were comprehensively investigated using first-principles calculations and the tight-binding approximation. These 1D MoX3 ACs, characterized by alternating Mo-Mo dimers, exhibit semiconducting behavior and a staggered antiferromagnetic (AFM) state, arising from the robust AFM direct exchange. The magnetocrystalline anisotropy energies are 1.079 meV/Mo for MoBr3 and 1.031 meV/Mo for MoI3. Fully noncollinear magnetic calculations reveal that magnetic spirals with helical angles theta = 2 pi/n (n = f2, f3, f4, ... , f infinity) possess higher energy than the collinear AFM state, confirming the AFM state as the ground state. Under tensile strain, structural transitions occur at 12% for MoBr3 and 6.5% for MoI3, with remarkable superelasticity up to 36% for MoBr3 and 38% for MoI3 before structural failure. Furthermore, carrier doping facilitates an AFM-to-FM phase transition, enabling 100% spin polarization. The lowest energy excitation involves domain walls with an energy of similar to 0.17 eV, readily achievable through moderate doping of optically excited electron-hole pairs. These findings provide profound insights into the electronic and magnetic characteristics of 1D MoX3 ACs, highlighting their significant potential for applications in spintronic and wearable flexible electronic devices.

Oxygen modification on the interface is crucial to improve the mechanical strength of graphene/copper (Gr/Cu) composites. However, the existing form of interface oxygen and the strengthening mechanisms are not well understood. In this work, first principles calculations are performed to investigate the mechanisms for oxygen modification in the Gr/Cu interface and the influences on the bonding behaviors. It is found that oxygen modification could increase the separation work of the Gr/Cu interface by about 300 %, and thus enhance the interface bonding substantially, owing to the formation of strong ionic bonds between O and Cu. As a result, the theoretical tensile strength is increased from 3.29 GPa to 4.67 GPa by 42 %. Changes in charge density and atomic spacing at the interface during stretching suggest that fracture occurs along the interface between graphene and O. This study provides valuable insights into the design of high-strength Gr/Cu composites.

Although defects such as vacancies may degrade the in-plane mechanical properties of graphene and carbon nanotube (CNT), they may also promote interfacial crosslinking and load transfer, and thus enhance the mechanical behavior of graphene- and CNT-based composites. The balance between these effects is crucial for optimizing the design of graphene- and CNT-based composites. Herein, molecular dynamics simulations were constructed to unravel the effect of vacancy-induced interfacial crosslinking on the mechanical behaviors of graphene/CNT composites. Higher defect concentrations led to a higher density of sp(3) C-C bonds at the interface, which reduced the tensile failure stress but increased the tensile failure strain. Meanwhile, the layer-by-layer failure transformed into a brittle failure. During compressive loading, the composites tended to buckle in the lower defect concentration range (<0.5 %) but exhibited outstanding buckling resistance at higher defect concentrations (5 %, 10 %). Shear loading led to wrinkling, and deformation instability was suppressed at the higher defect concentration, and all the composites demonstrated a layer-by-layer failure mode. Furthermore, the composites with a higher concentration of defects demonstrated excellent recoverable behavior during compressive loading. The results provide insights into the interface-dominated performance of graphene/CNT composites and help guide their design and fabrication.

Motion recognition and image preprocessing are critical for artificial vision systems, but there remains a need for more efficient and energy-saving devices with versatile image processing capabilities. Herein, we developed highly efficient photovoltaic detectors with bidirectional photocurrent and polarization-sensitive characteristics by sandwiching gold nanoparticles (Au NPs) between MoTe2 and ReS2, enabling two photoelectric units to operate collaboratively. The Au NPs induce localized surface plasmon resonance (LSPR) and hot electron injection, modulating the interface electronic structure, enhancing the light absorption efficiency, and extending the spectral response range to 1550 nm, surpassing the bandgap limitations of MoTe2 and ReS2. The responsivity and detectivity reach up to 8.35 A W-1 and 9.6 x 1011 Jones under 808 nm, respectively, which are about two orders of magnitude improvement over the pristine MoTe2/ReS2 device. The polarization ratio (PR) also increases from 4.7 to 9.1, which enables multi-task image processing applications. Leveraging the bidirectional photocurrent and polarization photo-response, the convolution processing is further combined with the device for realizing motion recognition and image processing tasks, including sharpening, edge extraction, and noise filtering. This work opens a new avenue for the development of Au NPs engineered photodetectors for image processing and motion recognition applications.

Lithium-ion batteries (LIBs) as an effective low carbon technology provide a solution for achieving NetZero emissions, in line with the Sustainable Development Goals set by the United Nations. Research efforts have been devoted to increasing the energy density and efficiency of LIBs. However, large-scale deployment of LIBs is challenged by thermal runaway and safety problems, particularly under abusive conditions. To tackle this challenge, we must gain insight into the safety features of batteries and design durable strategies by fundamentally analyzing battery thermal runaway processes. In this review, we systematically summarize the abusive indicators that may trigger the thermal issues at the macroscopic level from thermal, chemical, and mechanical perspectives, and point out failure mechanisms that correlate with each component, e.g., cathode, anode, separator, electrolyte and current collector. Beyond material innovations, we emphasize the importance of optimizing industrial-scale manufacturing, integrating regulatory frameworks through advanced battery management systems, and enhancing safety engineering from an battery external perspective. Moreover, we systematically evaluate the contributions of theoretical and computational approaches to battery safety, critically comparing physics-based, machine learning, and hybrid models, and proposing targeted improvements. The broader implications of these safety strategies are considered in the context of environmental sustainability and recycling. Finally, we present design principles for safer, high-performance batteries and outline emerging research and industrial directions through a critical synthesis of thermal runaway mechanisms and mitigation strategies.

Understanding the multi-bead overlapping process in wire-arc directed energy deposition (DED) is critical for the process and performance control of large superalloy components. In this work, a comprehensive analysis of the evolution of microstructure and mechanical properties of wire-arc DED of multi-bead Inconel 718 structure with oscillatory deposition mode was carried out. The correlation between deposition characteristics, thermal history, microstructure, and properties was established. The results indicate that multi-bead, as compared to single-bead, leads to coarser dendrites, frequent cracks, and pore defects in the overlap area by altering the thermal cycling in their vicinity. Meanwhile, the shape of the Laves phase here was transformed from small-sized islands to largesized long chains, and the overlap area still retains Laves phases of reduced size after heat treatment. This ultimately results in inhomogeneity in the mechanical properties of the deposited wall structure, severe reduction (similar to 78.9 %) of the tensile ductility, and a slight reduction (similar to 5 %) of the strength in the overlapping area. The fracture mechanism changes from ductile fracture to cleavage fracture in the overlap area. However, the superalloy deposited by the oscillation mode still maintains its high strength advantage, with a minimum yield strength of 1126 MPa. This study provides new insights for the optimization of the wire-arc DED process for large components of Inconel 718 superalloys and offers new insights into high-performance additive manufacturing of nickel-based superalloys.

Understanding on the transportation and mechanical properties of polycrystalline UO2 is critical for the development and design of high-performance nuclear fuels. However, the influence of grain boundaries (GBs) on the basic properties of UO2 has not been fully understood. Herein, a high-accuracy deep learning (DP) potential is constructed for UO2 based on a comprehensive database obtained from density functional theory (DFT) calculations. The melting, self-diffusion and phase transition of single-crystal UO2 are studied by molecular dynamics (MD) simulations using DP potential, demonstrating the excellent predictive capabilities of the DP potential. The DP potential could also well describe the local atomic structure of symmetrical tilt grain boundaries (STGBs) in UO2. UO2 bi-crystals exhibit the pre-melting at GBs during heating process. The self-diffusion of O is enhanced by all the GBs, whereas the self-diffusion of U atoms is only enhanced by the dislocations in low-angle STGBs. Brittle fracture occurs in UO2 bi-crystals at the lower temperatures (<1200 K), while amorphization takes place around GBs at high temperatures (>1200 K). This leads to brittle-to-ductile transition in polycrystalline UO2 at high temperature. The self-healing of pre-cracks in UO2 bi-crystals is determined by the diffusion of O and U atoms at high temperatures. The developed DP potential can be further applied in the studies on the microstructure design of UO2 based nuclear fuels.

The electrocatalytic performance of VSe2 doped with nonmetals (NMs) was studied using density functional theory, in which NM atoms (C, N, O, P, S, F, Cl, Br, and I) replaced Se or V (denoted as NM@Se or NM@V). Notably, P@V and Br@V monolayers exhibit high catalytic hydrogen evolution reaction activity with the lowest Delta G(H)* = 0.08 eV and -0.03 eV, respectively, surpassing Pt (Delta G(H)* = -0.1 eV). By applying the scaling relationship of Delta G(H)* of H*, which is an intermediate for each volcano, the exchange current density diagrams are established. Based on thermodynamic analysis, P@V and Br@V monolayers produce exchange currents of about -1.42 and -0.70i(0)/(A cm(-2)), respectively. The oxygen evolution reaction activity of the I@Se monolayer (eta(OER) = 0.95 V) is the best among all the monolayers. Among the oxygen reduction reaction catalysts, the O@Se monolayer displays high activity with a low eta(ORR) (0.82 V), which is even better than that of binary Pt and Pd alloys (0.9-0.87 V).

With increasing capacity of energy storage implemented into the power system services, a growing interest in evaluating the environmental impacts of energy storage systems (ESSs) has been sparked. In the present work, a comprehensive life cycle environmental hotspots assessment model for alternative ESSs was developed, including lithium iron phosphate battery (LIPB), vanadium redox flow battery, compressed air energy storage (CAES), supercapacitor and flywheel energy storage. A detailed life cycle inventory for the considered typical ESSs in China was provided to ensure the validity of the comparative assessment. It was indicated that the environmental impacts of ESSs were significantly dependent on technical solutions and grid application scenarios, including energy time-shift, frequency regulation, photovoltaic self-consumption, and renewable energy support. The results ranged from 26 to 702 kg CO2 eq/MWh for global warming potential (GWP), 0.1-1.2 kg PM2.5 eq/MWh for fine particulate matter formation, 0.1-3.0 kg SO2 eq/MWh for terrestrial acidification, 11-146 kg oil eq/MWh for fossil resource scarcity, and 0.0005-0.0122 kg N eq/MWh for marine eutrophication. LIPB emerged as a promising solution, while the environmental competitiveness of CAES increased in renewable-based power systems. It is advisable to prioritize the deployment of ESSs with minimal environmental footprints in the manufacturing process, such as CAES, despite the constraints imposed by relatively limited round-trip efficiencies. Moreover, the influences of the round-trip efficiency, depth of discharge, cycle frequency, and electrical grid emissions factor on the results were discussed. Particularly, the GWP of ESSs under the energy time-shift and frequency regulation scenarios decreased by approximately 3%-7% with a 1%-pts increase in the round-trip efficiency. Overall, the results could help manufacturers make informed decisions on energy storage materials selection. Besides, decision makers are recommended to consider multiple environmental impact indicators in devising future energy storage strategies.