Two-dimensional transition metal carbides (MXenes) have garnered significant attention due to their distinctive physical and chemical properties. In this study, utilizing density functional theory calculations, we introduce a novel phase of transition metal carbide with the space group of R3m, designated as α-MXene with the chemical formula M₂CX₂ (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn; X = O, F). Notably, α-MXene possesses an ABBCA atomic layer configuration closely resembles the two-dimensional ferroelectric material α-In₂Se₃, distinct from the close packing ABCAB atomic stacking observed in typical MXenes. It is highlighted that α-MXene exhibits adjustable ferroelectric properties with moderate polarization reversal energy barriers, including five rare ferroelectric metals and one Dirac-semimetal. Moreover, α-MXenes not only enable photocatalytic reactions by utilizing infrared light to overcome the band gap restriction of 1.23 eV, but also generate hydrogen and oxygen gases on separate surfaces due to electric field induced by ferroelectric effect. Additionally, ferroelectric tunnel junctions (FTJs) based on α-MXene show exceptionally high tunneling electroresistance ratios (TERs), indicating their suitability for advanced ferroelectric memory device applications. Our research provides a viable strategy for exploring ferroelectric materials within the expansive MXene family and exemplifies the applications of α-MXenes in photocatalysis and spintronics.

The highly alloyed Mg-10Gd-5Y-5Er alloy exhibits high strength, however, the brittle Mg₂₄RE₅ phase accelerates the initiation and development of micro-cracks and significantly deteriorate the plastic deformation ability. Therefore, it is necessary to regulate the type of precipitates to improve the comprehensive mechanical properties of the alloy. In this work, the influence of Zn content on mechanical properties and microstructure evolution of highly alloyed Mg-10Gd-5Y-5Er-xZn alloys (x = 0, 1, 2, 3, and 5 wt%) was investigated. It was found that the tensile strength increases with increasing Zn content, without deterioration of elongation. The maximum tensile yield strength and ultimate tensile strength are achieved to be 298 MPa and 406 MPa, respectively, within the studied concentration range. Thermodynamic calculations and microstructural characterization results indicate that with the increase of Zn content the precipitate transform from Mg₂₄RE₅ phase to long-period-stacking-ordered (LPSO) phase and lamellar structure. This transition will change the solute atom concentration in the matrix and affect the dynamic recrystallization behavior, thereby changing the contributions of solid solution strengthening and grain refinement strengthening to the yield strength of alloy. In particular, the blocky LPSO phase can significantly contribute to the increased strength at relatively high Zn contents (x > 2 wt%) by a mechanism similar to short-fiber strengthening. Moreover, the strategy of improving the mechanical properties by increasing the volume fraction of blocky LPSO phase can be applied to many Mg alloy systems containing LPSO phase.

Photocatalytic water splitting can convert solar energy into hydrogen, which has important implications for reducing dependence on fossil fuels. Constructing heterojunctions is a universal method for facilitating charge transfer, but the poor interface matching limits its charge separation and photocatalytic activity. Here, a metal-nickel bridging (nickel interlayer) NiO-Ni-Zn₂GeO₄ photocatalyst with well interface matching is designed through a partial oxidation strategy. Structure and in situ Raman characterization demonstrate that the nickel interlayer substantially optimizes interface matching and causes the first-order phonon mode transfer from the first-order longitudinal wave to the first-order transverse wave, which implies that NiO acts as the site for hydrogen production and violent surface reaction. Therefore, the nickel interlayer provides a charge transfer channel for carrier separation. Meanwhile, density functional theory calculations prove an optimal hydrogen-oxygen bond-breaking process with 36 % barriers decrease obtained via the effect of nickel interlayer. As a result, NiO-Ni-Zn₂GeO₄ shows the photocatalytic hydrogen production rate of 206.6 μmol g^-1 h^-1, which is over 8 times greater than that of Zn₂GeO₄. This study offers a new approach for designing heterojunctions with well-matched interface and efficient charge separation.

Liquid crystal polymers (LCPs) combine the entropic elasticity of polymers with the orderness of LC mesogens, demonstrating outstanding performance across diverse applications, particularly in bionic actuators. In contrast to the organisms that enable multi-stimuli responsibility, most LCP actuators reported thus far exhibit responsiveness to only a single stimulus, hence the fabrication of multi-stimuli responsive LCPs is of pronounced significance. Here, a novel multi-stimuli responsive LCP is developed by integrating ring-opening metathesis polymerization (ROMP) and post-polymerization modification (PPM), which exhibits reversible responsiveness to humidity, light, and pH. By spray-coating the stretched polypropylene with LCP, the bilayer actuator loads exceed 20 times its weight upon exposure to light irradiation and moisture, showcasing exceptional output force. Furthermore, in response to the change in pH and humidity, the actuator exhibits behaviors akin to natural flowers, including blooming, closing, and color-changing. The strategy combining ROMP and PPM has proven to be a versatile strategy for the synthesis of multifunctional LCPs, offering transformative potential for the development of advanced bionic actuators and soft robotic systems.