查看更多>>摘要：A 3D alpha-MoO3 nanostructure for high-performance triethylamine (TEA) detection was synthesized via the facial oxidation of MoS2 nanoflowers (NFs) obtained by a hydrothermal process. The influence of the time of hydrothermal process in growing MoS2 on the morphologies of the final MoO3 obtained after calcination was investigated. As-obtained MoO3 and their precursors were systematically characterized by various techniques, such as X-ray diffraction, Raman, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and N-2 adsorption-desorption isotherms. Results showed that MoO3 with a hierarchical layered nanostructure was successfully obtained. After hydrothermal treatment of the MoS2 precursor for 20 h, the typical MoO3-based sensor (called M20) exhibited a high response of 2.42 at a very low TEA concentration of only 0.1 ppm at 240 degrees C. The M20 sensor response to 50 ppm TEA was as high as 125 with a fast response/recovery time of 14/22 s. Moreover, the sensor had a high stability and reproducibility as well as a high selectivity against other interfering VOCs or gases. Due to the tendency of TEA to adsorb to active oxygen sites of MoO3, the enhanced sensing properties of MoO3 can be ascribed to the remarkable hierarchical structure and large surface area. MoO3 obtained after calcination of hydrothermally grown MoS2 is thus a promising sensing material for enhanced TEA gas detection. (C) 2021 Published by Elsevier Inc.
查看更多>>摘要：Here, we show that a reactive synthesis method of mixed elemental powders can be used to synthesize a porous electrode consisting of an intermetallic Fe5Si3 that exhibits catalytic activity towards oxygen evolution reaction (OER) in acidic solutions, which is capable of delivering 10 mA cm(-2) at an overpotential of 0.73 V and a small Tafel slope of similar to 381.8 mV dec(-1). The amorphous silica formed in the anode surface during the electrochemical process is multifunctional, as it protects the electrode substrate from corrosion and acts as electrocatalysts for OER. Remarkably, the Si-based intermetallics can be generalized to include other OER catalytic elements (Mn, Fe, Co), including Mn-Si and Co-Si intermetallics. (C) 2021 Elsevier Inc. All rights reserved.
查看更多>>摘要：Pancake-like TiO2 (M-TiO2) derived from the metal-organic framework was inlaid into three-dimensional flower-like BiOI through a facile solvothermal method. M-TiO2 supplies large surface area and mesoporous structure for attachment and transfer of the substrates and products, while BiOI acts as a photo sensitizer to absorb visible light and generates electrons and holes. The distinct structure of M-TiO2/BiOI gives a favorable contact between the two monomers, and promotes the transfer of charge carriers. In conjunction with the proper band positions of M-TiO2 and BiOI, the efficient separation of electron hole pairs is attained. Benefiting from the above cooperative effects of M-TiO2 and BiOI, the performance for the vanillin generation from sodium lignosulfonate (SLS) over M-TiO2/BiOI composites has a prominent improvement under visible light. Specifically, the yield over optimal M-TiO2/BiOI sample is about 5.8 mg/gSLS, obviously superior to that over pristine M-TiO2 (similar to 1 mg/gSLS) and BiOI (similar to 1.1 mg/gSLS). It is found that h(+) and O-center dot(2)- play the key role for vanillin generation from sodium lignosulfonate, and the low vanillin generation under UV-vis light sheds light on that (OH)-O-center dot is an adverse factor. We hoped that this work could inspire the studies on the photocatalytic valorization of biomass using noble metal-free catalysts. (C) 2021 Elsevier Inc. All rights reserved.
查看更多>>摘要：In the severe electromagnetic wave pollution situation, the absorbers must meet the requirements of lightweight, strong absorption, thin thickness and wide band. Under such a circumstance, it is of great significance to construct reasonable structure and composition for excellent electromagnetic wave absorption. Therefore, the Co/C composites anchored with carbon nanotubes (Co@CNTs) have been suc-cessfully prepared by rationally regulating the growth of bimetallic MOF and subsequent pyrolysis pro-cess. It is revealed that the conduction loss and polarization loss caused by the carbon nanotubes with different lengths and densities and the porosity of the composites are together responsible for the atten-uation of electromagnetic wave. As expected, the hierarchical Co@CNTs composites showed a strong reflection loss of-76.6 dB and a broad effective absorption bandwidth of 6.2 GHz through the improve-ment of impedance matching and electromagnetic wave absorption ability. Herein, this work presents a strategy for the development of composites as promising electromagnetic wave absorbent. (c) 2021 Published by Elsevier Inc.
查看更多>>摘要：Although the electrochemical production of hydrogen has been considered as a promising strategy to obtain the sustainable resources, the sluggish kinetics of anodic oxygen evolution reaction (OER) hindered the sustainable energy development. Herein, we design mesoporous cobalt ferrite phosphides hybridized on reduced graphene oxide (rGO) as a highly efficient bifunctional catalyst through a simple nanocasting method. The hybrid catalyst possesses the abundant interface, which provides the large active sites, as well as the hybrid rGO accelerates the electron exchange and ion diffusion. Moreover, the mesoporous structure not only prevents the aggregation of actives sites, but also benefits for the rapid escape of bubbles during catalytical process, which can significantly improve the catalytic performance. Consequently, the resulting mCo0.5Fe0.5P/rGO shows superior catalytic performance with a low overpotential of 250 mV at a current density of 10 mA cm2 for OER and outstanding long-term stability. More importantly, an electrolyzer with mCo0.5Fe0.5P/rGO as both anode and cathode catalysts shows a
查看更多>>摘要：In this work, rare-earth single atoms (La, Er) were decorated on the surface of 2D-TiO2 nanosheets by an impregnation-calcination strategy. The formation of rare-earth single atoms was certified by AC HAADF-STEM and XAS. TiO2 decorated with rare-earth single atoms (La-1-TiO2 and Er-1-TiO2) exhibited outstanding photocatalytic activity than pure 2D-TiO2 nanosheets (2D-TiO2) towards gas-phase degradation of O-xylene. Compared with 2D-TiO2, the rare-earth single atoms greatly improved the adsorption capacity of O-xylene without increasing their specific surface area. This is because rare-earth single atoms provide additional adsorption sites and reduce the adsorption energy of O-xylene. In addition, the hybrid orbital formed by the combination of rare-earth single atom and oxygen atom is beneficial to the rapid transmission and separation of photo-induced electrons, thereby improving the performance of photocatalytic degradation. In addition, in-situ DRIFTS and GC-MS were used to reveal the photocatalytic oxidation mechanism. Interestingly, the results showed that the La-1-TiO2 and Er-1-TiO2 samples can reduce the types of intermediates and simplify the reaction route, implying that the single atoms play an important role in the modulation and thorough mineralization of intermediate products. This work shows that the rare-earth single atom decorated 2D-TiO2 nanosheets have great potential in photocatalytic air pollution control. (C) 2021 Elsevier Inc. All rights reserved.
查看更多>>摘要：Hydroxyapatite (HAP) is the major mineral phase in bone and teeth. The interaction of individual amino acids and citrate ions with different crystallographic HAP surfaces has remained uncertain for decades, creating a knowledge gap to rationally design interactions with peptides, proteins, and drugs. In this contribution, we quantify the binding mechanisms and binding free energies of the 20 end-capped natural amino acids and citrate ions on the basal (001) and prismatic (01 0)/(0 2 0) planes of hydroxyapatite at pH values of 7 and 5 for the first time at the molecular scale. We utilized over 1500 steered molecular dynamics simulations with highly accurate potentials that reproduce surface and hydration energies of (hkl) hydroxyapatite surfaces at different pH values. Charged residues demonstrate a much higher affinity to HAP than charge-neutral species due to the formation of superficial ion pairs and ease of penetration into layers of water molecules on the mineral surface. Binding free energies range from 0 to -60 kJ/mol and were determined with similar to 10% uncertainty. The highest affinity was found for citrate, followed by Asp (-) and Glu(-), and followed after a gap by Arg(+), Lys(+), as well as by His(+) at pH 5. The (hkl)-specific area density of calcium ions, the protonation state of phosphate ions, and subsurface directional order of the ions in HAP lead to surface-specific binding patterns. Amino acids without ionic side groups exhibit weak binding, between -3 and 0 kJ/mol, due to difficulties to penetrate the first layer of water molecules on the apatite surfaces. We explain recognition processes that remained elusive in experiments, in prior simulations, discuss agreement with available data, and reconcile conflicting interpretations. The findings can serve as useful input for the design of peptides, proteins, and drug molecules for the modification of bone and teeth-related materials, as well as control of apatite mineralization. (C) 2021 Elsevier Inc. All rights reserved.
Maiyelvaganan, K. R.Kamalakannan, S.Shanmugan, S.Prakash, M....
9页
查看更多>>摘要：The attachment and dissociation of a proton from a water molecule and the proton transfers at solid-liquid interfaces play vital roles in numerous biological, chemical processes and for the development of sustainable functional materials for energy harvesting and conversion applications. Using first-principles computational methodologies, we investigated the protonated forms of polyhedral oligomeric silsesquioxane (POSS-H+) interacting with water clusters (Wn, where n = 1-6) as a model to quantify the proton conducting and localization ability at solid-liquid interfaces. Successive addition of explicit water molecules to POSS-H' shows that the assistance of at least three water molecules is required to dissociate the proton from POSS with the formation of an Eigen cation (H9O4+), whereas the presence of a fourth water molecule highly favors the formation of a Zundel ion (H5O2+). Reaction pathway and energy barrier analysis reveal that the formation of the Eigen cation requires significantly higher energy than the Zundel features. This confirms that the Zundel ion is destabilized and promptly converts in to Eigen ion at this interface. Moreover, we identified a Grotthuss-type mechanism for the proton transfer through a water chain close to the interface, where symmetrical and unsymmetrical arrangements of water molecules around H' of protonated POSS-H' are involved in the conduction of proton through water wires where successive Eigen-to-Zundel and Zundel-to-Eigen transformations are observed in quick succession. (C) 2021 Elsevier Inc. All rights reserved.
查看更多>>摘要：Wide-bandgap (WBG) perovskites play a crucial role for top cells in tandem solar cells (TSCs), which provides a promising avenue to boost the performance of widely used commercial solar cells. However, such WBG perovskite solar cells (PSCs) show poor performance compared to that of similar to 1.6 eV bandgap PSCs due to high defects density and photo-instability, resulting in relatively large open-circuit voltage loss (V-loss). Herein, we introduce alkali pseudo-halide KBF4 into the perovskite precursor solution for preparing less defect WBG perovskite film. It is showed that the interstitial occupancy of K+ in the perovskite lattice and the suppression of recombination by BF4, thereby inhibiting the ion migration and reducing the trap density. As a result, the champion WBG PSC (Energy gap (E-g), E-g = 1.74 eV) delivers a high open-circuit voltage (V-OC) of 1.21 V and a power conversion efficiency (PCE) of 17.49%. This work provides new insight into the defect tolerance upon metal pseudo-halides doping in the WBG perovskite. (C) 2021 Published by Elsevier Inc.
查看更多>>摘要：Lithium-rich layered oxides are believed to be the most competitive cathode materials for next -generation lithium-ion batteries (LIBs) due to their high specific capacity, but the poor cycle stability and voltage attenuation severely limit their commercial applications. In this paper, a simple method com-bining surface treatment via pyrolysis of polyvinyl alcohol (PVA) and potassium ions (K') doping, is designed to improve the above defects of the cobalt-free Lithium-rich material Li1.2Mn0.6Ni0.2O2 (LMR). The insoluble surface byproduct Li2CO3 and amorphous carbon nanolayer derived from the pyrolysis pro-cess of PVA alleviate the corrosion of acidic species with a favorable conductivity, while a large radius of K' can enlarge the space of the lithium (Li) layer to facilitate the diffusion of Li', suppress voltage polar-ization, and synchronously restrain the transformation from a layered structure to a spinel-like structure. After modification, the LMR material exhibits a great initial discharge capacity of 266.0 mAh g = 1 at 0.1C, a remarkable rate capability of 159.1 mAh g = 1 at 5C and an extremely high capacity retention of 98.5% over 200 cycles at 0.5C with a small voltage drop. (c) 2021 Elsevier Inc. All rights reserved.
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