Single-atom metal-nitrogen-carbon (M-N-C) catalysts have sparked intensive interests, however, the development of an atomically dispersed metal-phosphorus-carbon (M-P-C) catalyst has not been ...achieved, although molecular metal-phosphine complexes have found tremendous applications in homogeneous catalysis. Herein, we successfully construct graphitic phosphorus species coordinated single-atom Fe on P-doped carbon, which display outstanding catalytic performance and reaction generality in the heterogeneous hydrogenation of N-heterocycles, functionalized nitroarenes, and reductive amination reactions, while the corresponding atomically dispersed Fe atoms embedded on N-doped carbon are almost inactive under the same reaction conditions. Furthermore, we find that the catalytic activity of graphitic phosphorus coordinated single-atom Fe sharply decreased when Fe atoms were transformed to Fe clusters/nanoparticles by post-impregnation Fe species. This work can be of fundamental interest for the design of single-atom catalysts by utilizing P atoms as coordination sites as well as of practical use for the application of M-P-C catalysts in heterogeneous catalysis.
Conversion of CO2 to value-added chemicals has been a long-standing objective, and direct hydrogenation of CO2 to lower olefins is highly desirable but still challenging. Herein, we report a ...selective conversion of CO2 to lower olefins through CO2 hydrogenation over a ZnZrO/SAPO tandem catalyst fabricated with a ZnO-ZrO2 solid solution and a Zn-modified SAPO-34 zeolite, which can achieve a selectivity for lower olefins as high as 80–90% among hydrocarbon products. This is realized on the basis of the dual functions of the tandem catalyst: hydrogenation of CO2 on the ZnO-ZrO2 solid solution and lower olefins production on the SAPO zeolite. The thermodynamic and kinetic coupling between the tandem reactions enable the highly efficient conversion of CO2 to lower olefins. Furthermore, this catalyst is stable toward the thermal and sulfur treatments, showing the potential industrial application.
A ferrocene‐based ionic liquid (Fe‐IL) is used as a metal‐containing feedstock with a nitrogen‐enriched ionic liquid (N‐IL) as a compatible nitrogen content modulator to prepare a novel type of ...non‐precious‐metal–nitrogen–carbon (M‐N‐C) catalysts, which feature ordered mesoporous structure consisting of uniform iron oxide nanoparticles embedded into N‐enriched carbons. The catalyst Fe10@NOMC exhibits comparable catalytic activity but superior long‐term stability to 20 wt % Pt/C for ORR with four‐electron transfer pathway under alkaline conditions. Such outstanding catalytic performance is ascribed to the populated Fe (Fe3O4) and N (N2) active sites with synergetic chemical coupling as well as the ordered mesoporous structure and high surface area endowed by both the versatile precursors and the synthetic strategy, which also open new avenues for the development of M‐N‐C catalytic materials.
N‐enriched and Fe‐embedded ordered mesoporous carbon electrocatalysts were fabricated from an ionic liquid precursor by hard template synthesis. This strategy provides a high surface area and populated Fe‐N active sites with synergetic interaction for an optimized Fe10@NOMC catalyst. The catalyst shows excellent electrocatalytic efficiency and durability for the oxygen reduction in alkaline media.
This paper presents the development of wood flour (WF)-filled polylactic acid (PLA) composite filaments for a fused deposition modeling (FDM) process with the aim of application to 3D printing. The ...composite filament consists of wood flour (5 wt %) in a PLA matrix. The detailed formulation and characterization of the composite filament were investigated experimentally, including tensile properties, microstructure, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The feedstock filaments of this composite were produced and used successfully in an assembled FDM 3D printer. The research concludes that compared with pure PLA filament, adding WF changed the microstructure of material fracture surface, the initial deformation resistance of the composite was enhanced, the starting thermal degradation temperature of the composite decreased slightly, and there were no effects on the melting temperature. The WF/PLA composite filament is suitable to be printed by the FDM process.
Fused filament fabrication (FFF), also known as fused deposition modeling (FDM™), is considered one of the most promising additive manufacturing (AM) methods for its versatility, reliability and ...affordability. First adopted by industries for professional uses such as rapid prototyping, then by the general public in recent years, FFF has gathered itself considerable attention. Nevertheless, despite key advancements in printer technologies and filament materials, the fabrication of robust, performing and functional parts for high-demanding practical applications remains a significant challenge. Due to intrinsic deficiencies, such as the presence of voids and weak layer-to-layer adhesion, FFF-printed parts are plagued by weak and anisotropic mechanical properties in contrast to their conventionally manufactured counterparts. With the increasing demand for designable porous structures in the fields of biomedicine, 4D printing and lightweight cellular composites, understanding the challenges presented by void presence has become more relevant than ever. As existing literature has reviewed the significance of interlayer bonding, this review focuses on documenting recent insights on the formation of voids by its categorization, research method and mechanism. The primary objective is to provide a comprehensive understanding of the two current primary methods of void research—quantitative analysis and imaging. Detailed discussions on the effects of feedstock and printing parameters on void formation are also presented. Lastly, this review discusses gaps in the current research and outlines unaddressed challenges regarding void formation and its relation with the mechanical performance of FFF parts.
Studying the evolution history of the southwest summer monsoon (SSM) throughout geological time, particularly during its strongest period in the Holocene, can improve our understanding of its ...variation and driving mechanisms, and even help predict future climate changes, due to its significant social and economic implications. Here, we reconstructed the history of chemical weathering intensity since the Last Glacial Maximum (LGM) based on clay mineral proxies (illite/smectite)/(illite + chlorite) and illite crystallinity obtained from Qionghai Lake sediments and examined its response to paleoclimate and SSM. Our findings indicate that the intensity of chemical weathering generally aligned with changes in paleoclimate, exhibiting strong chemical weathering intensity during warm and humid climate conditions. In addition, the intensity of chemical weathering basically tracks the evolution of the SSM since the LGM. Our results support the view that the highest SSM intensity occurred during the early‐middle Holocene, followed by gradual weakening during the late Holocene, with Northern Hemisphere summer insolation being the primary driver of the SSM evolution. The variations of the SSM and the corresponding intensity of chemical weathering were also influenced by the cumulative effects of glacier boundary conditions, North Atlantic climate fluctuations, and Intertropical Convergence Zone migrations.
Key Points
Clay minerals can effectively reflect regional chemical weathering intensity
Chemical weathering intensity was following the monsoon variability
The strongest southwest summer monsoon occurred in the early‐middle Holocene
Abstract
As a red tide algal toxin with intense neurotoxicity distributed worldwide, domoic acid (DA) has attracted increasing concerns. In this work, the integrative analysis of metagenome and ...metabolome are applied to investigate the impact of DA on nitrogen cycling in coastal sediments. Here we show that DA can act as a stressor to induce the variation of nitrogen (N) cycling by altering the abundance of functional genes and electron supply. Moreover, microecology theory revealed that DA can increase the role of deterministic assembly in microbial dynamic succession, resulting in the shift of niches and, ultimately, the alteration in N cycling. Notably, denitrification and Anammox, the important process for sediment N removal, are markedly limited by DA. Also, variation of N cycling implies the modification in cycles of other associated elements. Overall, DA is capable of ecosystem-level effects, which require further evaluation of its potential cascading effects.
In this work, we report a novel and facile procedure for a one-pot preparation of palladium nanoparticle catalysts supported on porous N-doped carbon (Pd@CNT) by direct carbonization of ...palladium-N-heterocyclic carbene coordination polymer (P-Pd-NHC). This method could be conveniently extended to the synthesis of the Ni and alloy (Pd x Ni y ) nanoparticle catalysts (Ni@CN800, Pd x Ni y @CN800). The treatment temperature played an important role on the growth and properties of the resultant M@CNT, wherein M@CN800 carbonized at 800 °C showed well-monodispersed metal nanoparticles (MNPs), graphene-like layers of the N-doped carbon supports, and strong interaction between MNPs and the support. Pd@CN800 displayed high efficiency and stable recyclability toward the domino carbonylative synthesis of pyrazole derivatives. Interestingly, its catalytic performance has been even higher than that of the representative PdCl2(PPh3)2 within six runs.
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