Abstract The identification of the contribution of different surface sites to the catalytic activity of a catalyst nanoparticle is one of the most challenging issues in the fundamental studies of heterogeneous catalysis. We herein demonstrate an effective strategy of using a series of uniform cubic Cu 2 O nanocrystals with different sizes to identify the intrinsic activity and contributions of face and edge sites in the catalysis of CO oxidation by a combination of reaction kinetics analysis and DFT calculations. Cu 2 O nanocrystals undergo in situ surface oxidation forming CuO thin films during CO oxidation. As the average size of the cubic Cu 2 O nanocrystals decreases from 1029 nm to 34 nm, the dominant active sites contributing to the catalytic activity switch from face sites to edge sites. These results reveal the interplay between the intrinsic catalytic activity and the density of individual types of surface sites on a catalyst nanoparticle in determining their contributions to the catalytic activity.
Abstract Triple‐conducting (H + /O 2− /e − ) cathodes are a vital constituent of practical protonic ceramic fuel cells. However, seeking new candidates has remained a grand challenge on account of the limited material system. Though triple conduction can be achieved by mechanically mixing powders uniformly consisting of oxygen ion–electron and proton conductors, the catalytic activity and durability are still restricted. By leveraging this fact, a highly efficient strategy to construct a triple‐conductive region through surface self‐assembly protonation based on the robust double‐perovskite PrBaCo 1.92 Zr 0.08 O 5+δ , is proposed. In situ exsolution of BaZrO 3 ‐based nanoparticles growing from the host oxide under oxidizing atmosphere by liberating Ba/Zr cations from A/B‐sites readily forms proton transfer channels. The surface reconstructing heterostructures improve the structural stability, reduce the thermal expansion, and accelerate the oxygen reduction catalytic activity of such nanocomposite cathodes. This design route significantly boosts electrochemical performance with maximum peak power densities of 1453 and 992 mW cm −2 at 700 and 650 °C, respectively, 86% higher than the parent PrBaCo 2 O 5+δ cathode, accompanied by a much improved operational durability of 140 h at 600 °C.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Abstract Developing sustainable and lightweight structural materials is a promising strategy for reducing carbon emissions in transportation and buildings. However, producing high‐performance bulk structural materials from sustainable biomass materials while maintaining excellent mechanical strength remains a major challenge, especially for further scale‐up. Herein, a scalable and robust bottom‐up strategy is reported to fabricate bulk wooden plate (W‐plate) with a typical “brick‐and‐mortar” structure from engineered wood particles via moderate delignification and in situ LiCl/DMAc treatment followed by hot‐pressing. The W‐plate constructed by delignified wood particles and regenerated cellulose nanofibers can achieve a confluence of mechanical strengthening and toughening by the ordered lamination structure and multiscale cellulose micro/nanofiber crosslinking interactions, resulting in high flexural strength (225.17 ± 12.18 MPa) and high fracture toughness (4.01 ± 0.53 MPa m 0.5 ) while maintaining a low density (1.34 g cm −3 ), superior to typical metals and ceramics. Moreover, the W‐plate exhibits advantageous thermal properties, including a low thermal expansion coefficient (<19 × 10 −6 K −1 ) and a high storage modulus (>7.5 GPa) compared to those of petroleum‐based polymers. Coupled with abundant and renewable raw materials, all‐cellulose components, and scalable and recyclable fabrication, the W‐plate can potentially be used as a high‐performance, cost‐effective, and environmentally friendly alternative for engineering applications.
Abstract Surface frustrated Lewis pairs (SFLPs) have been implicated in the gas‐phase heterogeneous (photo)catalytic hydrogenation of CO 2 to CO and CH 3 OH by In 2 O 3− x (OH) y . A key step in the reaction pathway is envisioned to be the heterolysis of H 2 on a proximal Lewis acid–Lewis base pair, the SFLP, the chemistry of which is described as In⋅⋅⋅In‐OH + H 2 → In‐OH 2 + ⋅⋅⋅In‐H − . The product of the heterolysis, thought to be a protonated hydroxide Lewis base In‐OH 2 + and a hydride coordinated Lewis acid In‐H − , can react with CO 2 to form either CO or CH 3 OH. While the experimental and theoretical evidence is compelling for heterolysis of H 2 on the SFLP, all conclusions derive from indirect proof, and direct observation remains lacking. Unexpectedly, we have discovered rhombohedral In 2 O 3− x (OH) y can enable dissociation of H 2 at room temperature, which allows its direct observation by several analytical techniques. The collected analytical results lean towards the heterolysis rather than the homolysis reaction pathway.
Well-defined bimetallic heterogeneous catalysts are not only difficult to synthesize in a controlled manner, but their elemental distributions are also notoriously challenging to define. Knowledge of these distributions is required for both the as-synthesized catalyst and its activated form under reaction conditions, where various types of reconstruction can occur. Success in this endeavor requires observation of the active catalyst via in situ analytical methods. As a step toward this goal, we present a composite material composed of bimetallic nickel-ruthenium nanoparticles supported on a protonated zeolite (Ni-Ru/HZSM-5) and probe its evolution and function as a photoactive carbon dioxide methanation catalyst using in situ X-ray absorption spectroscopy (XAS). The working Ni-Ru/HZSM-5, as a selective and durable photothermal CO2 methanation catalyst, comprises a corona of Ru nanoparticles decorating a Ni nanoparticle core. The specific Ni-Ru interactions in the bimetallic particles were confirmed by in situ XAS, which reveals significant electron transfer from Ni to Ru. The light-harvesting Ni nanoparticle core and electron-accepting Ru nanoparticle corona serve as the CO2 and H2 dissociation centers, respectively. These Ni and Ru nanoparticles also promote synergistic photothermal and hydrogen atom transfer effects. Collectively, these effects enable an associative CO2 methanation reaction pathway while hindering coking and fostering high selectivity toward methane.
Magnetic van der Waals (vdW) layered materials has inspired enormous interest recently by utilizing the spin degree of freedom for applications in next-generation 2D spintronic devices. Among these materials, MnBi2Te4 provides topological bands and the alternating ferromagnetic / antiferromagnetic ordering simultaneously, thus serves as an ideal system promising for 2D spintronics. However, many controversies and discrepancies between theoretical predictions and experimental observations remain unclarified, mainly due to unclarified correlations between electronic bands and surface magnetic ordering. Here, we performed intensive studies of low temperature scanning tunneling microscopy/spectroscopy (STM/S) on high-quality single crystal of MnBi2Te4, rationalized with density functional theory (DFT) calculations. Topological surface states (TSSs) and the dispersions are clearly observed by quasiparticle interference (QPI) imaging. The asymmetric QPI patterns at the energies near Dirac point, strongly suggest that the magnetization of the Mn layer in the topmost septuple-layer can be canted into the in-plane direction, which is responsible for the observations of gapless TSSs. Furthermore, various bulk bandgaps observed at the temperatures below and above the Nèel temperature or at the edge of surface terraces, implies a variety of band structures correlated with rich magnetic orders in the surface Mn layer. Our results provide an in-depth understanding of correlations between topological electronic structures and magnetic ordering of surface layer in magnetic topological insulator MnBi2Te4, as well as spin-dependent transport properties in spintronic devices.
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