Universal Synthesis of Half-Metallic Diatomic Catalysts for Efficient Oxygen Reduction Electrocatalysis.

Developing efficient and low-cost noble-free metal electrocatalysts is an urgent requirement. Herein, a one-step, solid-state template-assisted method for fabricating isolated half-metallic diatomic M, Zn─N─C (M═Fe, Co, and Ni) catalysts is reported. In particular, the fabricated Fe, Zn─N─C structure exhibits superior oxygen reduction reaction capabilities with a half-wave potential of 0.867 V versus RHE. The Mossbauer spectra reveal that the Fe, Zn─N─C half-metallic diatomic catalyst has a large proportion of the D2 site (ferrous iron with a medium spin state). Density functional theory (DFT) reveals that in Fe, Zn─N─C structures, the zinc sites play a unique role in accelerating the protonation process of O2 in ORR. In assembled zinc-air batteries, a maximum power density of 138 mW cm-2 and a capacity of 748 mAh g zn-1 can be obtained. This work fabricates a series of efficient M, Zn─N─C diatomic electrocatalysts, and the developed solid-state reaction method can hopefully apply in other energy conversion and storage fields.

Colloidal Stabilization of Submicron-Sized Zeolite NaA in Ethanol-Water Mixtures for Nanostructuring into Thin Films and Nanofibers.

Despite the growing use of organic or mixed solvents in zeolite processing, most studies focus only on aqueous suspension systems. We investigated the colloidal characteristics of submicron-sized zeolite NaA in mixed ethanol-water solvents. The effects of the mixing ratio of solvents and various additives on the dispersion of the zeolite powders were studied. The zeolite NaA particles were destabilized in solvent mixtures at a high ethanol-to-water ratio, a reduction in the zeta potential was observed, and the destabilization was rationalized by the Derjaguin, Landau, Verwey, Overbeek (DLVO) theory. An improved stabilization of the zeolite NaA suspensions was achieved in ethanol-rich solvent mixtures using nonionic low molecular weight organic additives, but not with their ionic counterparts such as anionic, cationic surfactants or inorganic acids or bases. Polyethylene glycol (PEG)-400 was found to be a good dispersant for the submicron-sized zeolite NaA particles in the ethanol-water mixtures, which was attributed to its interaction with the zeolite surface, leading to an increased zeta potential. The PEG-stabilized zeolite suspensions led to low suspension viscosities as well as uniform and consistent spin-coated films.

Pansharpening Model of Transferable Remote Sensing Images Based on Feature Fusion and Attention Modules.

The purpose of the panchromatic sharpening of remote sensing images is to generate high-resolution multispectral images through software technology without increasing economic expenditure. The specific method is to fuse the spatial information of a high-resolution panchromatic image and the spectral information of a low-resolution multispectral image. This work proposes a novel model for generating high-quality multispectral images. This model uses the feature domain of the convolution neural network to fuse multispectral and panchromatic images so that the fused images can generate new features so that the final fused features can restore clear images. Because of the unique feature extraction ability of convolution neural networks, we use the core idea of convolution neural networks to extract global features. To extract the complementary features of the input image at a deeper level, we first designed two subnetworks with the same structure but different weights, and then used single-channel attention to optimize the fused features to improve the final fusion performance. We select the public data set widely used in this field to verify the validity of the model. The experimental results on the GaoFen-2 and SPOT6 data sets show that this method has a better effect in fusing multi-spectral and panchromatic images. Compared with the classical and the latest methods in this field, our model fusion obtained panchromatic sharpened images from both quantitative and qualitative analysis has achieved better results. In addition, to verify the transferability and generalization of our proposed model, we directly apply it to multispectral image sharpening, such as hyperspectral image sharpening. Experiments and tests have been carried out on Pavia Center and Botswana public hyperspectral data sets, and the results show that the model has also achieved good performance in hyperspectral data sets.

Two-Dimensional LDH Film Templating for Controlled Preparation and Performance Enhancement of Polyamide Nanofiltration Membranes.

Tailored design of high-performance nanofiltration membranes that can be used in a variety of applications such as water desalination, resource recovery, and sewage treatment is desirable. Herein, we describe the use of layered double hydroxides (LDH) intermediate layer to control the interfacial polymerization between trimesoyl chloride (TMC) and piperazine (PIP) for the preparation of polyamide (PA) membrane. The dense surface of LDH layer and its unique mass transfer behavior influence the diffusion of PIP, and the supporting role of the LDH layer allows the formation of ultrathin PA membranes. By only changing the concentration of PIP, a series of membranes with controllable thickness from 10 to 50 nm and tunable crosslinking-degree can be prepared. The membrane prepared with a higher concentration of PIP shows excellent performance for divalent salt retention with water permeance of 28 Lm-2 h-1 bar-1 , high rejection of 95.1 % for MgCl2 and 97.1 % for Na2 SO4 . While the membrane obtained with a lower concentration of PIP can sieve dye molecules of different sizes with a flux of up to 70 Lm-2 h-1 bar-1 . This work demonstrates a novel strategy for the controllable preparation of high-performance nanofiltration membranes and provides new insights into how the intermediate layer affects the IP reaction and the final separation performance.

Janus Hollow Nanofiber with Bifunctional Oxygen Electrocatalyst for Rechargeable Zn-Air Battery.

Zn-air battery technologies have received increasing attention, while the application is hindered by the sluggish kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In order to explore an efficient method to fabricate a high-performance electrocatalyst via modification of advanced nanostructure, a coaxial electrospinning method with in-situ synthesis and subsequent carbonization to construct 3D flexible Janus-like electrocatalysts is developed. The resulting Janus nanofibers have a unique core-shell hollow fiber structure, where NiFe alloy electrocatalysts supported by N-doped carbon nanobelt are located on the inner wall of the carbon layer, and leaf-like Co-N nanosheets are anchored on the outer wall of the carbon layer. As a result, the electrocatalyst exhibits excellent bifunctional catalytic performance for ORR and OER, demonstrating the small potential gap value of 0.73 V between the ORR half-wave potential and the OER potential at 10 mA cm-2 , which is even comparable to the mixed commercial noble catalyst with 20% Pt/C and RuO2 . The rechargeable Zn-air battery is constructed and displays a large open-circuit voltage of 1.44 V, high power density (130 mW cm-2 ) and energy density (874 Wh kg-1 ). This study provides a concept to synthesize and construct high performance bifunctional electrocatalysts.

Random Occupation of Multimetal Sites in Transition Metal-Organic Frameworks for Boosting the Oxygen Evolution Reaction.

Developing robust oxygen evolution reaction (OER) electrocatalysts with excellent performance is essential for the conversion of renewable electricity to clean fuel. Herein, we present a facile concept for the synthesis of efficient high-entropy metal-organic frameworks (HEMOFs) as electrocatalysts in a one-step solvothermal synthesis. This strategy allows control of the microstructure and corresponding lattice distortion by tuning the metal ion composition. As a result, the OER activity was improved by optimizing the coordination environment of the metal catalytic center. The optimized Co-rich HEMOFs exhibited a low overpotential of 310 mV at a current density of 10 mA cm-2 , better than a RuO2 catalyst tested under the same conditions. The finding of lattice distortion of the HEMOFs provides a new strategy for developing high-performance electrocatalysts for energy conversion.

Alkali-Etched Ni(II)-Based Metal-Organic Framework Nanosheet Arrays for Electrocatalytic Overall Water Splitting.

The exploration of efficient electrocatalysts is the central issue for boosting the overall efficiency of water splitting. Herein, pertinently creating active sites and improving conductivity for metal-organic frameworks (MOFs) is proposed to tailor electrocatalytic properties for overall water splitting. An Ni(II)-MOF nanosheet array is presented as an ideal material model and a facile alkali-etched strategy is developed to break its NiO bonds accompanied with the introduction of extra-framework K cations, which contribute to creating highly active open metal sites and largely improving the electrical conductivity. As a result, the assembled defect-Ni-MOF||defect-Ni-MOF electrolyte cell delivers a lower and stable voltage of 1.50 V at 10 mA cm-2 in alkaline medium for overall water splitting, comparable to the combination of iridium and platinum as benchmark catalysts.

Functionalized Base-Stable Metal-Organic Frameworks for Selective CO2 Adsorption and Proton Conduction.

Metal-organic frameworks (MOFs) have shown great potential for application in various fields, including CO2 capture and proton conduction. For promoting their practical applications, both optimization of a given property and enhancement of chemical stability are crucial. In this work, three base-stable isostructural MOFs, [Ni8 (OH)4 (H2 O)2 (BDP-X)6 ] (Ni-BDP-X; H2 BDP=1,4-bis(4-pyrazolyl)benzene, X=CHO, CN, COOH) with different functional groups, are designed, synthesized, and used in CO2 capture and proton conduction experiments. They possess face-centered cubic topological structures with functional nanoscale cavities. Importantly, these MOFs are fairly stable to maintain their structures in boiling water and 4 M sodium hydroxide solution at room temperature. Functionalization endows them with tunable properties. In gas adsorption studies, these MOFs exhibit selective adsorption of CO2 over CH4 and N2 , and in particular the introduction of COOH groups provides the highest selectivity. In addition, the COOH-functionalized Ni-BDP exhibits a high proton conductivity of 2.22×10-3  S cm-1 at 80 °C and approximately 97 % relative humidity.

Zr-based metal-organic frameworks: design, synthesis, structure, and applications.

Among the large family of metal-organic frameworks (MOFs), Zr-based MOFs, which exhibit rich structure types, outstanding stability, intriguing properties and functions, are foreseen as one of the most promising MOF materials for practical applications. Although this specific type of MOF is still in its early stage of development, significant progress has been made in recent years. Herein, advances in Zr-MOFs since 2008 are summarized and reviewed from three aspects: design and synthesis, structure, and applications. Four synthesis strategies implemented in building and/or modifying Zr-MOFs as well as their scale-up preparation under green and industrially feasible conditions are illustrated first. Zr-MOFs with various structural types are then classified and discussed in terms of different Zr-based secondary building units and organic ligands. Finally, applications of Zr-MOFs in catalysis, molecule adsorption and separation, drug delivery, and fluorescence sensing, and as porous carriers are highlighted. Such a review based on a specific type of MOF is expected to provide guidance for the in-depth investigation of MOFs towards practical applications.

DFT-Based Simulation and Experimental Validation of the Topotactic Transformation of MgAl Layered Double Hydroxides.

The thermal topotactic transformation mechanism of MgAl layered double hydroxides (LDHs) is investigated by a combined theoretical and experimental study. Thermogravimetric differential thermal analysis (TG-DTA) results reveal that the LDH phase undergoes four key endothermic events at 230, 330, 450, and 800 °C. DFT calculations show that the LDH decomposes into CO2 and residual O atoms via a monodentate intermediate at 330 °C. At 450 °C, the metal cations almost maintain their original distribution within the LDH(001) facet during the thermal dehydration process, but migrate substantially along the c-axis direction perpendicular to the (001) facet; this indicates that the metal arrangement/dispersion in the LDH matrix is maintained two-dimensionally. A complete collapse of the layered structure occurs at 800 °C, which results in a totally disordered cation distribution and many holes in the final product. The structures of the simulated intermediates are highly consistent with the observed in situ powder XRD data for the MgAl LDH sample calcined at the corresponding temperatures. Understanding the structural topotactic transformation process of LDHs would provide helpful information for the design and preparation of metal/metal oxides functional materials derived from LDH precursors.

Transparent, Ultrahigh-Gas-Barrier Films with a Brick-Mortar-Sand Structure.

Transparent and flexible gas-barrier materials have shown broad applications in electronics, food, and pharmaceutical preservation. Herein, we report ultrahigh-gas-barrier films with a brick-mortar-sand structure fabricated by layer-by-layer (LBL) assembly of XAl-layered double hydroxide (LDH, X=Mg, Ni, Zn, Co) nanoplatelets and polyacrylic acid (PAA) followed by CO2 infilling, denoted as (XAl-LDH/PAA)n-CO2. The near-perfectly parallel orientation of the LDH "brick" creates a long diffusion length to hinder the transmission of gas molecules in the PAA "mortar". Most significantly, both the experimental studies and theoretical simulations reveal that the chemically adsorbed CO2 acts like "sand" to fill the free volume at the organic-inorganic interface, which further depresses the diffusion of permeating gas. The strategy presented here provides a new insight into the perception of barrier mechanism, and the (XAl-LDH/PAA)n-CO2 film is among the best gas barrier films ever reported.

Zeolitic Imidazolate Framework-Derived Pt-Co in Nanofibrous Networks as Stable Oxygen Reduction Electrocatalysts with Low Pt Loading.

Proton-exchange membrane fuel cell technology is a key component in the future zero-carbon energy system, generating power from carbon-free fuels, such as green hydrogen. However, the high Pt loading in conventional fuel cell electrodes to maintain electrocatalytic activity and durability, especially on the cathode for oxygen reduction, is the Achilles heel for the worldwide deployment of fuel cell technologies. To minimize Pt consumption for oxygen reduction, we synthesized Pt-Co-based electrocatalysts with meticulous structuring from micrometer to the atomic scale based on reaction pathways. The resulting Pt-Co-based electrocatalysts contain only 1.9 wt% Pt, which is 20 times lower than the conventional Pt-C catalysts for fuel cells. By utilizing electrospinning and in situ synthesis, we anchored three-dimensionally structured zeolitic imidazolate frameworks on continuously connected nanofibrous electrospun mats. The Pt-Co@Pt-free nanowire (PC@PFN) electrocatalysts contain Pt-Co nanoparticles (NPs) and non-Pt elements, Co-containing sites comprising NPs, nanoclusters, and N-coordinated Co single atoms. Despite the ultralow Pt loading in PC@PFN, the mass activity exceeds the U.S. Department of Energy 2025 target by 2.8 times and retains 85.5% of the initial activity after 80,000 durability test cycles, possibly owing to synergistic reaction pathways between Pt and non-Pt sites.

Flexible CoAl LDH@PEDOT core/shell nanoplatelet array for high-performance energy storage.

A CoAl-layered double hydroxide (LDH)@poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell nanoplatelet array (NPA) is grown on a flexible Ni foil substrate as a high-performance pseudocapacitor. The LDH@PEDOT core/shell NPA shows a maximum specific capacitance of 649 F/g (based on the total mass) by cyclic voltammetry (scan rate: 2 mV/s) and 672 F/g by galvanostatic discharge (current density: 1 A/g). Furthermore, the hybrid NPA electrode also exhibits excellent rate capability with a specific energy of 39.4 Wh/kg at a current density of 40 A/g, as well as good long-term cycling stability (92.5% of its original capacitance is retained after 5000 cycles). These performances are superior to those of conventional supercapacitors and LDH NPA without the PEDOT coating. The largely enhanced pseudocapacitor behavior of the LDH@PEDOT NPA electrode is related to the synergistic effect of its individual components: the LDH nanoplatelet core provides abundant energy-storage capacity, while the highly conductive PEDOT shell and porous architecture facilitate the electron/mass transport in the redox reaction.

Aqueous Chloride-Ion Battery within a Neutral Electrolyte Based on a CoFe-Cl Layered Double Hydroxide Anode.

Aqueous chloride-ion batteries (ACIBs) with environmental friendliness and high safety hold great potential to fulfill the green energy demand for ocean desalination. Herein, for the first time, a composite consisting of Cl--intercalated CoFe layered double hydroxides (CoFe-Cl-LDH) cross-linked with CNTs (CoFe-Cl-LDH/CNT) is synthesized and demonstrated to be a novel high-performance anode for ACIBs in a neutral NaCl aqueous solution. While exhibiting a high initial capacity of ∼190 mAh g-1 at 200 mA g-1, CoFe-Cl-LDH/CNT is capable of delivering a reversible capacity of ∼125 mAh g-1 after 200 cycles. At a high current density of 400 mA g-1, it still holds a capacity of ∼120 mAh g-1. The excellent Cl- storage performance can be contributed to the unique topochemical transformation feature that reverses intercalation/deintercalation of Cl- along with valence changes of Co2+/Co3+ and Fe2+/Fe3+ during charge/discharge and the improved electronic conductivity by hybridizing with CNTs. It is interesting that the invertible insertion/extraction of interlayer H2O was discovered, which could be beneficial to the capacity after cycles to a certain extent. The Cl--intercalated LDH material declared in this work shows its feasibility on Cl- capture/release in aqueous anion-type batteries and provides a new opportunity for future development of ACIBs or aqueous desalination technology.

An MgAl layered double hydroxide as a new transition metal-free anode for lithium-ion batteries.

A carbonate intercalated magnesium aluminum layered double hydroxide is used as an anode material for lithium-ion batteries, displaying a maximum discharge specific capacity of 814 mA h g-1 at 200 mA g-1 in this work through utilizing the valence variation of Mg and the conversion between LiOH and LiH/Li2O.

Aided diagnosis of cervical spondylotic myelopathy using deep learning methods based on electroencephalography.

Cervical spondylotic myelopathy (CSM) is the most severe type of cervical spondylosis. It is challenging to achieve early diagnosis with current clinical diagnostic tools. In this paper, we propose an end-to-end deep learning approach for early diagnosis of CSM. Electroencephalography (EEG) experiments were conducted with patients having spinal cord cervical spondylosis and age-matched normal subjects. A Convolutional Neural Network with Long Short-Term Memory Networks (CNN-LSTM) model was employed for the classification of patients versus normal individuals. In contrast, a Convolutional Neural Network with Bidirectional Long Short-Term Memory Networks and attention mechanism (CNN-BiLSTM-attention) model was used to classify regular, mild, and severe patients. The models were trained using focal Loss instead of traditional cross-entropy Loss, and cross-validation was performed. Our method achieved a classification accuracy of 92.5 % for the two-class classification among 40 subjects and 72.2 % for the three-class classification among 36 subjects. Furthermore, we observed that the proposed model outperformed traditional EEG decoding models. This paper presents an effective computer-aided diagnosis method that eliminates the need for manual extraction of EEG features and holds potential for future auxiliary diagnosis of spinal cord-type cervical spondylosis.

Solution plasma synthesis of Pt-decorated Bi12O17Cl2 photocatalysts for efficient upcycling of plastics.

Photocatalytic upcycling of plastic waste is a promising approach to relieving pressure caused by solid waste, but the rational design of novel efficient photocatalysts remains a challenge. Herein, we utilize subnano-sized platinum (Pt)-based photocatalysts for plastic upcycling. A solution plasma strategy is developed to fabricate Pt-decorated Bi12O17Cl2 (SP-BOC). The Pt in an oxidant state and oxygen vacancies optimize the electronic structure for fast charge transfer. As a result, SP-BOC displays high performance for upcycling polyvinyl chloride (PVC) and polylactic acid (PLA) into acetic acid and formic acid, with yield rate and selectivity of 6.07 mg g-1cat. h-1 and 94 %, and 47.43 mg g-1cat. h-1 and 55.1 %, respectively. In addition, the dichlorination efficiency of PVC reaches 78.1 % within 10 h reaction, effectively reducing the environmental hazards associated with PVC waste disposal treatments. This research provides insight into the effective conversion of plastics into high-value chemicals, contributing to the reduction of carbon and toxic emissions in a practical and meaningful way, and offering a useful way for solving challenges of waste management and environmental sustainability.

High entropy alloy nanoparticles encapsulated in graphitised hollow carbon tubes for oxygen reduction electrocatalysis.

High entropy alloys (HEAs) with a tunable alloy composition and fascinating synergetic effects between various metals have attracted significant attention in the field of electrocatalysis, but their potential is limited by inefficient and unscalable fabrication methodologies. This work proposes a novel solid-state thermal reaction method to synthesise HEA nanoparticles encapsulated in an N-doped graphitised hollow carbon tube. This facile method is simple and efficient and involves no use of organic solvents during the fabrication process. The synthesized HEA nanoparticles are confined by the graphitised hollow carbon tube, which is possibly beneficial for preventing the aggregation of alloy particles during the oxygen reduction reaction (ORR). In a 0.1 M KOH solution, the HEA catalyst FeCoNiMnCu-1000(1 : 1) exhibits an onset and half-wave potential of 0.92 V and 0.78 V (vs. RHE), respectively. We assembled a Zn-Air battery with FeCoNiMnCu-1000 as a catalyst for the air electrode, and a power density of 81 mW cm-2 and a long-term durability of >200 h were achieved, which is comparable to the performance of the state-of-the-art catalyst Pt/C-RuO2. This work herein offers a scalable and green method for synthesising multinary transition metal-based HEAs and highlights the potential of HEA nanoparticles as electrocatalysts for energy storage and conversion.

Temperature-controlled electrochemical switch based on layered double hydroxide/poly(N-isopropylacrylamide) ultrathin films fabricated via layer-by-layer assembly.

In this paper we report the fabrication of layered double hydroxide (LDH) nanoparticles/poly(N-isopropylacrylamide) (pNIPAM) ultrathin films (UTFs) via the layer-by-layer assembly technique, and their switchable electrocatalytic performance in response to temperature stimuli was demonstrated. X-ray diffraction and UV-vis absorption spectroscopy indicate a periodic layered structure with uniform and regular growth of the (LDH/pNIPAM)(n) UTFs; an interaction based on hydrogen bonding between LDH nanoparticles and pNIPAM was confirmed by X-ray-photoelectron spectroscopy and Fourier transform infrared spectroscopy. Temperature-triggered cyclic voltammetry and electrochemical impedance spectroscopy switch for the UTFs was obtained between 20 and 40 °C, accompanied by reversible changes in surface topography and film thickness revealed by atomic force microscopy and ellipsometry, respectively. The electrochemical on-off property of the temperature-controlled (LDH/pNIPAM)(n) UTFs originates from the contraction-expansion configuration of pNIPAM with low-high electrochemical impedance. In addition, a switchable electrocatalytic behavior of the (LDH/pNIPAM)(n) UTFs toward the oxidation of glucose was observed, resulting from the temperature-controlled charge transfer rate. Therefore, this work provides a facile approach for the design and fabrication of a well-ordered command interface with a temperature-sensitive property, which can be potentially applied in electrochemical sensors and switching.

MgAl Saponite as a Transition-Metal-Free Anode Material for Lithium-Ion Batteries.

Transition-metal compounds (oxides, sulfides, hydroxides, etc.) as lithium-ion battery (LIB) anodes usually show extraordinary capacity larger than the theoretical value due to the transformation of LiOH into Li2O/LiH. However, there has rarely been a report relaying the transformation of LiOH into Li2O/LiH as the main reaction for LIBs, due to the strong alkalinity of LiOH leading to battery deterioration. In this work, layered silicate MgAl saponite (MA-SAP) is applied as a -OH donor to generate LiOH as the anode material of LIBs for the first time. The MA-SAP maintains a layered structure during the (dis)charging process and has zero-strain characteristic on the (001) crystal plane. In the discharging process, Mg, Al, and Si in the saponite sheets become electron-rich, while the active hydroxyl groups escape from the sheets and combine with lithium ions to form LiOH in the "caves" on sheets, and the LiOH continues to decompose into Li2O and LiH. Consequently, the MA-SAP delivers a maximum capacity of 536 mA h·g-1 at 200 mA·g-1 with a good high-current discharging ability of 155 mA h·g-1 after 1000 cycles under 1 A·g-1. Considering its extremely low cost and completely nontoxic characteristics, MA-SAP has great application prospects in energy storage. In addition, this work has an enlightening effect on the development of new anodes based on extraordinary mechanisms.