Latest ArticlesSi coordination structures have been proven to greatly influence the ammonia-selective catalytic reduction (NH3-SCR) catalytic properties and the hydrothermal stability of Cu-based silicoaluminophosphate-form catalysts. However, the role of various Si coordination structures in the NH3-SCR reaction over Cu-SAPO-34 catalyst remains unknown. Herein, a batch of Cu-SAPO-34 samples with various Si contents was synthesized via a one-pot method to study the role of Si coordination structures in the NH3-SCR catalytic properties and hydrothermal stability. Cu/34–2 with the highest proportion of Si(xOAl) (x = 1~3) structures exhibits remarkable durability with 90% NO reduction efficiency within 200~450 ℃ even after a hydrothermal aging treatment at 850 ℃. In contrast, Cu/34–1 and Cu/34–4 with the highest proportions of Si(4OAl) and Si(0OAl) structures, respectively, are significantly deactivated by the same hydrothermal treatment. To better understand this phenomenon, the relationship between the Si coordination structures and SCR performance is established using characterization techniques and kinetics measurements. Results reveal that a high content of Si(4OAl) and Si(0OAl) is detrimental to the hydrothermal stability of Cu-SAPO-34 catalyst. However, Si(xOAl) (x = 1~3) structures are conducive to the stabilization of isolated Cu2+, thus enhancing the stability to severe hydrothermal treatment.
Various advanced microwave absorbing materials have been developed for reducing/avoiding the harm of microwave radiation. Among them, core-shell structural nanomaterials have been widely fabricated for microwave absorption. However, the "structure-performance" relationship between shell thickness and microwave absorption performance is rarely reported. In this paper, we first explored the "structure-performance" relationship between shell thickness and microwave absorption performance, based on the core-shell α-Fe2O3@SiO2 nanoparticles with a constant α-Fe2O3-core size and changeable SiO2-shell thickness. With increasing the SiO2-shell thickness, the microwave absorption ability first increased, then decreased. Under a proper SiO2-shell thickness of 35 nm, α-Fe2O3@SiO2 sample achieved the strongest microwave absorbing ability with a reflection loss minimum value of –4.3 dB, better than that of pure α-Fe2O3 (–3.8 dB). This enhanced microwave absorption performance was mainly derived from the dielectric loss. Although the absolute value of the reflection loss was relatively low (–4.3 dB), this study shed an important reference on designing next-generation advanced iron oxide-based materials for microwave absorption.
Despite the continuously increased requirement on automated synthesis of medicines for distributed manufacturing and personal care, it remains a challenge to realize automated synthesis which requires solid-liquid phase reactions. In this work, we demonstrated an automated solid-liquid synthesis for gadopentetate dimeglumine, the most widely used magnetic resonance imaging (MRI) contrast agent. The high-efficiency reaction was performed in a 3D microfluidic chip which was fabricated by femtosecond laser micromachining. The structure of the chip realized 3D shear flow which was essential for highly efficient mixing and movement of the solid-liquid mixtures. Ultraviolet visible (UV-vis) spectrometer was employed for in-line analysis to help automation of this system. Comparing with the round-bottom flask system, this synthetic system showed significantly higher reaction rate, indicating the advantage of the 3D microfluidic technology in micro chemical engineering.
A novel iron-hydrogen battery system, whose Fe3+/Fe2+ cathode circumvents slowly dynamic oxygen reduction reaction and anode is fed with clean and cordial hydrogen, is systematically investigated. The maximum discharge power density of the iron-hydrogen battery reaches to 96.0 mW/cm2 under the room temperature. The capacity reaches to 17.2 Ah/L and the coulombic and energy efficiency are achieved to 99% and 86%, respectively, during the galvanostatic charge-discharge test. Moreover, stable cycling test is observed for more than 240 h and 100 cycles with the iron sulfate in the sulfuric acid solutions. It is found that air plasma treatment onto the cathode carbon paper can generate the oxygen-containing groups and increase the hydrophilic pores proportion to ca. 40%, enlarging nearly 6-fold effective diffusion coefficient and improving the mass transfer in the battery performance. The simple iron-hydrogen energy storage battery design offers us a new strategy for the large-scale energy storage and hydrogen involved economy.
Nitric oxide reduction to ammonia by electrocatalysis is the potential application in the elimination of smog and energy conversion. In this work, the feasibility of the application of two-dimensional metal borides (MBenes) in nitric oxide electroreduction reaction (NOER) was investigated through density functional theory calculations. Including the geometry and electronic structure of five kinds of MBenes, the adsorption of NO on the surface of these substrates, the selective adsorption of hydrogen protons during the hydrogenation process, and the overpotential in the electrocatalytic ammonia synthesis process. As a result, MnB exhibited the most favorable catalytic performance according to the associative pathways, which is thermodynamically performed spontaneously, and WB has a minimum overpotential of 0.37 V vs. RHE in the process of ammonia production according to the dissociative pathway. Overall, our work is the first to explore the electrocatalytic NO through the dissociative mechanism to synthesize ammonia in-depth and proves that MBenes are efficient NO electrocatalytic ammonia synthesis catalysts. These research results provide a new direction for the development of electrocatalytic ammonia synthesis experimentally and theoretically.
The development of effective and low-energy-consumption catalysts for CO2 conversion into high-value-added products by constructing versatile active sites on the surface of heterogeneous compounds is an urgent and challenging task. In this study, a stable and well-defined heterogeneous cobalt hexacyanocobaltate (Co3[Co(CN)6]2), typical cobalt Prussian blue analogue (CoCo-PBA) modified with tetrabutylammonium bromide (TBAB), is proven to be the superior catalyst for CO2 and epoxide coupling to produce cyclic carbonates with > 99% yield under mild reaction conditions (1.0 MPa, 65 ℃). Based on a series of characterizations, it is revealed that the CoCo-PBA structure can maintain relatively high thermal and chemical stability. Recycling experiments exhibited that the CoCo-PBA system could retain 98% of the original activity after six reaction rounds. The CoCo-PBA/TBAB catalytic system was also highly active for coupling CO2 with other industrial-grade epoxides. These results show the CoCo-PBA catalytic system potential flexibility and the generality of the catalyst preparation strategy.
Wood-derived carbons have been demonstrated to have large specific capacities as the anode materials of lithium-ion batteries (LIBs). However, these carbons generally show low tap density and minor volumetric capacity because of high specific surface area and pore volume. Combination with metal oxide is one of the expected methods to alleviate the obstacles of wood-derived carbons. In this work, the composites of MnO loaded wood-derived carbon fibers (CF@MnO) were prepared via a simple and environmentally friendly method, showing decreased specific surface area due to the generation of MnO nanoparticles on carbon fibers. Furthermore, the CF@MnO compostites exhibit superior electrochemical performance as anode materials of LIBs, which show high reversible capacity in the range of 529–734 mAh/g at a current density of 100 mA/g. The optimal CF@MnO product (MnO: carbon = 1:2) delivers reversible capacity of 734 and 265.3 mAh/g at current density of 100 and 2000 mA/g, respectively. Besides, the material presents outstanding stability with coulombic efficiency around 100% after 200 cycles at a high current density of 400 mA/g, revealing a potential as promising anode materials for high-performance LIBs.
We comment the recent paper which reported a series of TPA derivatives to show acid-induced tunable white light emission.
Nature consists of various soft tissues with well-ordered hierarchical anisotropic structures, which play essential roles in biological systems to exhibit particular functions. Mimicking bio-tissues, synthetic hydrogels with anisotropic structures have received considerable attention in recent years. However, existing approaches to fabricate anisotropic hydrogels often require complicated procedures, which are time-consuming and labor-demanding. Inspired by the dry-induced crystallization phenomenon, we report a simple yet effective prestretching-drying-swelling method to afford anisotropic crystalline polyvinyl alcohol hydrogels. Owing to the distinct anisotropic microstructure, the hydrogels demonstrate excellent mechanical properties with noticeable directional distinction. It is revealed that both the enhancing of pre-orientation strain and the extending of heating time make the hydrogels with better mechanical properties and more remarkable anisotropicity. Owing to the anisotropically aligned structure, the hydrogels exhibit remarkably differential ionic conductivity: the difference between the parallel and vertical conductivity of the same sample can reach as high as 6.6 times, making the materials possible candidates as nano-conductive materials. We anticipate that this simple yet effective approach may become highly useful for fabricating oriented hydrogels and endow the materials with more promising application prospects in the future.
A simple and effective method for constructing highly efficient oxygen reduction catalysts with trace amount of isolated cobalt was firstly developed by the pyrolysis of Co-centered polyoxometalate@metal-organic framework (Co-POM@MOF). The Co-centered polyoxometalate ([CoW12O40]6−) was confined in the well-defined void space of ZIF-8 to achieve homogeneous dispersion of polyoxoanions, where the isolated Co centers were well surrounded by the W-O shell and ZIF-8 framework. The Co-POM@MOF-derived N-doping porous carbon (Co-W-NC) with trace cobalt content was facilely prepared by the pyrolysis of the Co-POM@MOF under Ar atmosphere. The single dispersion of polyoxoanions in the metal-organic framework with complete separation of Co center surrounding by W-O shell and ZIF-8 framework ensures the uniform dispersion of Co atoms, confirmed by the Fourier transform extended X-ray absorption fine structure measurement. The Co-W-NC composite catalysts exhibit high performance for oxygen reduction reactions with a half-wave potential of 0.835 V in 0.1 mol/L KOH solution with excellent durability, which is much superior to that of the control samples derived from the [PW12O40]@ZIF-8, and the commercial Pt/C. This work highlights a new insight for constructing highly efficient catalysts via the introduction of metal-centered polyoxometalate into metal-organic framework following the high temperature treatment process.
No. 86 Xueyuan South Road, Haidian District, Beijing
010-62199257
qkjq@cast.org.cn
Copyright © 2025 China Association for Science and Technology. All rights reserved. For all open access content, the relevant licensing terms apply.
Sponsored by the Office of the Leading Group for Cybersecurity and Informatization of CAST, and supported by Science and Technology Review Publishing House
