Communications Materials最新文献

Platinum (Pt) is recognized as the most active material for the hydrogen evolution reaction in acidic media; however, its catalytic activity is often underestimated in proton exchange membrane water electrolysis (PEMWE) due to poor utilization of the cathode catalyst layer. In this study, we present the synthesis, characterization, and application of Pt nanoparticles with atomic precision on a microporous-layer-coated gas diffusion layer for PEMWE. The Pt nanoparticles were synthesized via atomic layer deposition, a technique that enables precise control over loading and particle size at the atomic scale. The resulting gas diffusion electrode with an exceptionally low platinum loading (1.08-5.40 μg cm^{- 2}) demonstrated mass activity at least one order of magnitude higher than that of benchmark Pt. Furthermore, the electrode exhibited exceptional stability at a current density of 1 A cm^{- 2} over 200 hours. It also showed robust performance under dynamic operation, enduring 25,000 cycles of alternating cell voltages between 1.45 V and 2 V.

Two-dimensional (2D) aluminum nitride (AlN) represents a promising material with unique properties predicted by density functional theory (DFT), characterized by a honeycomb lattice where Al and N atoms exhibit threefold in-plane coordination. However, the synthesis of free-standing AlN nanosheets has been challenging due to the crystal configurations of the well-known bulk AlN, which presents a hexagonal wurtzite structure with a tetrahedral coordination, preventing its exfoliation to obtain nanosheets. Herein, we propose a facile method involving the preparation of layered-structured aluminum carbonitrides, Al₅C₃N, followed by exfoliation into AlN nanosheets, offering a potential route for producing 2D AlN. The Al₅C₃N precursor was chemically etched in hydrofluoric acid (HF), breaking the Al-C bonds and exposing the AlN nanosheets. The development of this synthesis method opens up opportunities towards the preparation of 2D AlN and the investigation of its unique properties for applications in sensors and microelectronics.

Thin film growth is a critical process enabling modern applications ranging from electronic devices to advanced coatings. Among the parameters that govern thin film growth, the Ehrlich-Schwoebel barrier stands out with its tight control over interlayer transfer and, consequently, kinetics-dominated film morphology. Despite its importance, the precise measurement of the Ehrlich-Schwoebel barrier remains complicated, presenting a critical impediment to rational thin film design. Here, we provide an insight into the Ehrlich-Schwoebel barrier over monoatomic step edges on Au (111) surfaces via three-dimensional atomic force microscopy (3D-AFM) with sub-nanometer spatial precision, minimizing the need for empirical model assumptions or theoretical calculations. Our measurements provide a quantitative, real-space view of the complex potential energy and force landscape near step edges, verifying the presence of energy barriers and wells at the top and bottom of step edges, respectively. The effect of the herringbone reconstruction on the potential energy landscape is also analyzed, revealing an enhancement of interactions near the elbows and a slight attenuation of the ridges.

Direct reduction of iron oxide using hydrogen offers a sustainable route to lower carbon emissions in steelmaking. Although iron oxide feedstocks consist of polycrystalline pellets, the influence of initial hematite grain size on direct reduction remains unexplored. Herein, the effect of grain size on reduction kinetics and microstructure evolution were uncovered using model polycrystalline hematite samples with large ( ~ 30 µm) and ultrafine ( ~ 1 µm) grains. Thermogravimetric analysis showed grain-size-dependent reduction behavior, while microstructural examination of partially reduced samples revealed that large-grained hematite forms finer directional pore channels due to fewer grain boundaries and orientation changes. Consequently, large-grained samples reduce faster initially as the pore network develops, while ultrafine-grained samples achieve more efficient reduction in later stages facilitated by a more homogenous pore network. These results demonstrate how grain size dictates porosity and texture evolution, providing fundamental insights relevant not only to hydrogen-based iron production but also to the design of porous materials by solid-state reduction processes.

The integration of high-quality, ultrathin van der Waals (vdW) dielectrics with 2D semiconductors remains a critical bottleneck in the development of reliable, ultra-scaled field-effect transistors (FETs). Here, we report a comprehensive study of MoS₂-based FETs employing layered rhombohedral MnAl₂S₄ as the gate insulator, a previously unexplored vdW dielectric that can be isolated down to the monolayer limit. Devices fabricated in both top-gated (TG) and bottom-gated (BT) configurations exhibit excellent electrical performance, featuring low gate leakage, minimal hysteresis ( < 2 mV) under high electric fields up to 11 MV cm^-1 across a wide range of gate voltage sweep rates (0.001-10 Vs^-1). We observed a consistent counterclockwise hysteresis and an anomalous bias temperature instability (BTI), possibly caused by the diffusion of Mn interstitials and S vacancies formed inside the MnAl₂S₄ film during growth. Notably, we show that threshold voltage degradation at high temperatures was observed to be negligible, and hysteresis dynamics and very small BTI are reproducible over a long time, demonstrating the high reliability of our devices. In addition, the vdW interface between MnAl₂S₄ and MoS₂ in our device is of good quality and is expected to provide a small density of insulator defects, a promising gate dielectric for reliable 2D devices.