Physics

The diverse polymorphic phases of 2D materials constitute a unique platform for property engineering, making precise phase control a pivotal enabler for next-generation electronics. This review provides a comprehensive survey of recent advances in the phase engineering of 2D materials, with a focus on metal chalcogenides that exhibit rich polymorphism and stoichiometry-dependent structural variations. We begin by outlining the expansive phase space and corresponding property spectrum, spanning semiconducting, metallic, insulating, and ferroelectric states. We then delve into the fundamental principles and experimental methodologies for precise phase manipulation, including pathways toward phase-pure synthesis and both irreversible and reversible phase transformations, while highlighting the governing roles of thermodynamics, kinetics, and stoichiometry. Furthermore, we showcase how these strategies enable revolutionary device concepts, such as high-performance 2D transistors, phase-change memories, and ferroelectric devices. Finally, we discuss the remaining challenges and future perspectives in achieving scalable integration and dynamic phase control, underscoring the transformative potential of phase engineering in advancing the field of 2D electronics.

The micro/nanoporous materials that have both hierarchical pore structures and robust mechanical properties would have broad implications for areas ranging from damping and filter separation to adsorbent materials; however, creating such micro/nanoporous materials has proven extremely challenging. Herein, the multifunctional aerogel-structured metafabrics composed of wholly porous microspheres and nanofibril scaffolds are fabricated by innovatively integrating millisecond microphase separation molding technology with multi-parameter coupling control strategy. The aerogel-like porous microspheres with abundant vortex sheets can be realized by customizing the Taylor cone ejection morphology and regulating the bidirectional mass-transfer between the external environment and solvents. The hierarchical pore structure consisting of micro/nanofibrous networks and porous aerogel microspheres is developed, which endows metafabrics with high porosity (>90%). Attributed to the flexible and stable structure of micro/nanofibrils, the resulting aerogel-structured metafabrics exhibit mechanical robustness and shape-memory property even under -196°C. Moreover, such aerogel structures endow the metafabrics with surprising potential for energy dissipation and filtration separation, particularly ultrathin noise reduction (NRC of 0.5 at 10 mm), high-efficiency air filtration (99.96% efficiency, 23.3 Pa air resistance), and high-utilisation CO₂ capture (0.68 mmol g^-1) at extremely low amine loading, obviously superior to cutting-edge materials. This work provides a new pathway for the design of multifunctional aerogel-structured metafabrics.

Multilayer ceramic capacitors (MLCCs) are promising candidates for miniaturizing advanced electronic systems, owing to their high-power density and rapid discharge capabilities. However, simultaneously achieving high energy density and near-zero energy loss remains a long-standing challenge, hindering their application potential as next-generation energy-storage devices. Here, we propose a bottom-up self-assembly strategy within a disordered (Sr_0.2Ca_0.2Pb_0.2Na_0.2La_0.2)TiO₃ high-entropy ceramic matrix to construct a nanodomain configuration. The high-entropy design guarantees a locally compositional inhomogeneous platform with fully lowered energy barrier for dipole switching, and the subsequent substitution of strong polar Bi effectively facilitates the progress of nanodomain assembly. The synergistic regulation of lattice structure and anisotropic domain configuration gives rise to relaxor antiferroelectric-like polarization behavior, simultaneously enabling high polarization intensity and fast dipole switching. Consequently, a concurrent breakthrough with a high energy density of 24.7 J cm^-3 and an ultrahigh efficiency of 96.5% is achieved in the antiferroelectric-like high-entropy superparaelectric MLCCs. This work establishes a new opportunity for manipulating polarization profiles and designing high-performance energy storage dielectrics.

Conformal integration of flexible electronics with unstandardized biological tissues is critical for next-generation wearables. However, flexible devices are predominantly fabricated in conventional planar formats, incompatible with the nonplanar, hairy, or dynamic surfaces of biological organisms. Here, we resolve this conflict by introducing a universal solid-liquid-solid phase transition strategy. This approach utilizes water-soluble polyvinyl alcohol as a substrate, which temporarily liquefies and flows to match target topography upon wetting, then solidifies in place, enabling a perfect conformal interface. Such a process helps the reconstructed devices to establish robust (interfacial toughness ∼29 J m^-2, tensile strength of ∼161 kPa), stretchable, and stress-free interfaces with skin. Furthermore, this robust interface permits reversible switching between strong to weak adhesion, while dissolving on-demand for painless, non-traumatic removal. We validate the approach with shape-adaptable sensors and electrodes that seamlessly wrap the vulnerable, peristaltic bodies of silkworms for motion tracking, and hairy, thorn-laden leaves for plant electrophysiology monitoring, expanding the utility of wearable electronics to previously inaccessible biological surfaces.

Rechargeable hydrogen gas batteries show a great promise for large-scale energy storage due to their high safety, environmental friendliness, high efficiency and long-cycle life. However, the costly catalysts at the anode for hydrogen oxidation/evolution reactions (HOR/HER) hinder the practicability. Here, we report a pseudo-single-crystal mesoporous (PSCM) PtPd catalyst with high HOR/HER bifunctional activities for high-performance hydrogen gas batteries. It exhibits an outstanding HOR activity with a kinetic current density of 3.10 A mg^-1 and an HER overpotential of 34.8 mV at 10 mA cm^-2, outperforming commercial Pt/C (0.42 A mg^-1, 79.3 mV). When assembling Ni-H₂ battery with a low PSCM-PtPd catalyst loading of ∼45 µg cm^-2, it displays a high energy efficiency of ∼85% and cycling stability of >1000 cycles. Even at an ultra-low catalyst loading of ∼10 µg cm^-2, the Ni-H₂ (PSCM-PtPd) battery still exhibits an energy density of ~135 Wh kg^-1 and durability of >1000 cycles with a cell cost of ~105 $ kWh^-1, much better than that of Pt/C-based battery (>700 $ kWh^-1). We demonstrate that the superior activity of the PSCM-PtPd catalyst originates from the charge transfer from Pd to Pt and lattice distortion caused by Pd incorporation, and the enhanced stability is attributed to its fewer grain boundaries and stable attachment to the electrode. This work offers a promising pathway toward designing cost-effective and scalable energy storage systems.