Interconnected Porous Network Research Articles

Evaluation of a novel nanocrystalline hydroxyapatite powder and a solid hydroxyapatite/Chitosan-Gelatin bioceramic for scaffold preparation used as a bone substitute material.

Artificially fabricated hydroxyapatite (HAP) shows excellent biocompatibility with various kinds of cells and tissues which makes it an ideal candidate for a bone substitute material. In this study, hydroxyapatite nanoparticles have been prepared by using the wet chemical precipitation method using calcium nitrate tetra-hydrate [Ca(NO3)2.4H2O] and di-ammonium hydrogen phosphate [(NH4)2 HPO4] as precursors. The composite scaffolds have been prepared by a freeze-drying method with hydroxyapatite, chitosan, and gelatin which form a 3D network of interconnected pores. Glutaraldehyde solution has been used in the scaffolds to crosslink the amino groups (|NH2) of gelatin with the aldehyde groups (|CHO) of chitosan. The X-ray diffraction (XRD) performed on different scaffolds indicates that the incorporation of a certain amount of hydroxyapatite has no influence on the chitosan/gelatin network and at the same time, the organic matrix does not affect the crystallinity of hydroxyapatite. Transmission electron microscope (TEM) images show the needle-like crystal structure of hydroxyapatite nanoparticle. Scanning Electron Microscope (SEM) analysis shows an interconnected porous network in the scaffold where HAP nanoparticles are found to be dispersed in the biopolymer matrix. Fourier transforms infrared spectroscopy (FTIR) confirms the presence of hydroxyl group (OH-) , phosphate group (PO3-4) , carbonate group (CO2-3) , imine group (C=N), etc. TGA reveals the thermal stability of the scaffolds. The cytotoxicity of the scaffolds is examined qualitatively by VERO (animal cell) cell and quantitatively by MTTassay. The MTT-assay suggests keeping the weight percentage of glutaraldehyde solution lower than 0.2%. The result found from this study demonstrated that a proper bone replacing scaffold can be made up by controlling the amount of hydroxyapatite, gelatin, and chitosan which will be biocompatible, biodegradable, and biofriendly for any living organism.

Porous asymmetric microfiltration membranes shaped by combined alumina freeze and tape casting

An assembled asymmetric alumina microfiltration membrane with high performance was prepared by combining freeze and tape casting techniques followed by two sintering steps. Freeze casting was used for manufacturing of the porous support layer with a highly interconnected pore network. Tape casting was applied on the top layer to form a pre-membrane with smaller pore size and controlled thickness, which was set on the sintered support. Morphology influences were investigated for different solid loadings, additives content and the assembled layer membrane structures. No delamination among the layers was observed. The assembled ceramic membrane had an average pore size between 30 and 50 μm together with a top surface layer around 0.35 μm, which is suitable to the microfiltration separation process. Porosity in the range of 26–50 % and water flux of 11–32 m3 m−2 h−1 bar−1 were reached for samples prepared with two sintering steps at 1600 and 1300 °C for 2 h.

Intrinsically Bioactive Cryogels Based on Platelet Lysate Nanocomposites for Hemostasis Applications.

The currently used hemostatic agents are highly effective in stopping hemorrhages but have a limited role in the modulation of the wound-healing environment. Herein, we propose an intrinsically bioactive hemostatic cryogel based on platelet lysate (PL) and aldehyde-functionalized cellulose nanocrystals (a-CNCs). PL has attracted great attention as an inexpensive milieu of therapeutically relevant proteins; however, its application as a hemostatic agent exhibits serious constraints (e.g., structural integrity and short shelf-life). The incorporation of a-CNCs reinforced the low-strength PL matrix by covalent cross-linking its amine groups that exhibit an elastic interconnected porous network after full cryogelation. Upon blood immersion, the PL-CNC cryogels absorbed higher volumes of blood at a faster rate than commercial hemostatic porcine gelatin sponges. Simultaneously, the cryogels released biomolecules that increased stem cell proliferation, metabolic activity, and migration as well as downregulated the expression of markers of the fibrinolytic process. In an in vivo liver defect model, PL-CNC cryogels showed similar hemostatic performance in comparison with gelatin sponges and normal material-induced tissue response upon subcutaneous implantation. Overall, owing to their structure and bioactive composition, the proposed PL-CNC cryogels provide an alternative off-the-shelf hemostatic and antibacterial biomaterial with the potential to deliver therapeutically relevant proteins in situ.

BiSb@Bi2O3/SbOx encapsulated in porous carbon as anode materials for sodium/potassium-ion batteries with a high pseudocapacitive contribution

Sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are emerging next-generation energy storage technology, and exploiting applicative electrode materials to accommodate the large-sized Na+ and K+ are urgently needed. Herein, an innovative composite of BiSb@Bi2O3/SbOx nanoparticles encapsulated in porous carbon (BiSb@Bi2O3/SbOx@C) is fabricated through a template-assisted in-situ pyrogenic decomposition and evaluated as anodes for SIBs and PIBs. The BiSb@Bi2O3/SbOx@C delivers high specific capacity, superior rate capability (205 mA h g−1 and 111 mA h g−1 at 2 Ah g−1) and good cycling stability (248 mA h g−1 and 214 mA h g−1 after 500 cycles at 1 A g−1) in SIBs and PIBs. The excellent performance owes to the synergistic effect of Bi and Sb, the multilayer nanostructure design as well as the interconnected porous carbon network, which effectively promotes electron transport and ion diffusion, restricts volume change and enhances the electrode structure stability simultaneously. Furthermore, the capacitive behavior contributes much to the storage of sodium and potassium ions, which guarantees a superior rate capability. This research opens up new opportunities for exploring high-performance anodes for SIBs and PIBs.

Effective membrane backwash with carbon dioxide under severe fouling and operation conditions

Membrane fouling is an intrinsic deficiency common for all membrane processes. Fouling mitigation is therefore required to achieve sustainable membrane performance. Our study suggests a novel backwash concept which utilizes network of ultrafiltration interconnected membrane pores as a substrate for CO2 bubbles nucleation from a saturated CO2 solution which enters membrane pores from the support side. As a result, enhanced fouling removal was achieved due to additional hydrodynamic forces caused by expanded and lifted CO2 bubbles. An investigation of CO2 nucleation kinetics using a high speed camera revealed that initial CO2 nucleation rate is strongly determined by the module height and feed water type. A saturated CO2 solution backwash effectively removed bovine serum albumin (BSA) which caused both internal and external membrane fouling. A fouling reduction was also observed in BSA/seawater matrix opposite to cake layer buildup observed experiments with Milli-Q backwash. CO2 nucleation allowed to remove hydraulically irreversible fouling which was caused by transparent exopolymer particles (TEP) at pH 4 and 8. This is a promising result as TEP is biofouling precursor which tends to adsorb to a membrane surface making conventional cleaning practices inefficient. Complete transmembrane pressure recovery was achieved with a feed water containing sodium alginate and SiO2 nanoparticles with sizes compatible with membrane pores. The observed results emphasized the importance of the specific interactions in membrane/foulant/CO2 bubble triangle for a successful membrane recovery.

3D porous oxygen-enriched graphene hydrogels with well-balanced volumetric and gravimetric performance for symmetric supercapacitors

3D porous oxygen-enriched graphene hydrogels (POGHs) have been successfully prepared via a one-step hydrothermal approach with graphene oxide and a tiny amount of acidic glutamic acid which serves as carboxyl source, reductant, nitrogen dopant, as well as pore size and density regulator at the same time. Owing to the high content of oxygen-containing functional groups and high density, the repaired graphene sheet structure by nitrogen doping, 3D interconnected porous networks and large specific surface areas, the as-obtained POGHs binder-free electrodes exhibit excellent electrochemical properties in 6 M KOH electrolyte. In particular, the POGH-30-based symmetric supercapacitor displays well-balanced volumetric capacitance (241.1 F cm−3) and gravimetric capacitance (256.5 F g−1) at 0.5 A g−1, and this capacitance can be maintained for 91.8% even at 10 A g−1. Moreover, the POGH-30 electrode also delivers high gravimetric and volumetric specific energy densities of 8.8 Wh kg−1 and 8.3 Wh L−1 at 0.5 A g−1, and excellent cycling stability of 100.7% retention after 10000 cycles at 10 A g−1. These results denote that POGH-30 is expected to be used as electrode material for high-performance supercapacitors.

PREPARATION AND ELECTROCHEMICAL BEHAVIOR OF THE ACTIVATED CARBON FROM POMEGRANATE PEELS AS ENERGY-STORAGE MATERIALS

This study investigates the electrochemical evaluation of the activated carbon (AC) prepared from pomegranate peels which were collected, dried, carbonized and finally activated with KOH at different temperatures. The characterization of the as-prepared AC revealed an amorphous type of carbon and densely layer-stacking sheets with an interconnected micro porous network with a remarkable 3128.86m2g-1 surface area. The as-synthesized AC displayed a remarkable capacitance of 126 F g-1 at 0.5 A g-1with a storage retention of 137 % after 2000 cycles at a current density of 2 A g-1. Meanwhile, the realistic symmetrical simulation has been installed, it shows an energy density of 4.58 W h kg-1 at a power density of 244 W kg-1 with a storage retention of 66 % of the initial capacity at a current density of 2 A g-1 after 2000 cycles. Overall, these results demonstrate that for supercapacitors evaluation, the AC electrode can be considered a successful electrode material.

Functionalized geopolymer foams for cesium removal from liquid nuclear waste

Geopolymer foam hosting a 3D network of interconnected pores was synthetized and functionalized with a potassium copper hexacyanoferrate [K2CuFe(CN)6] in order to decontaminate radioactive liquid waste containing cesium. The Geopolymer Foam (GF) and Functionalized Geopolymer Foams (FGF) were characterized using a panel of characterization techniques (SEM, TEM, XRD …) before studying their capacity to remove selectively cesium from the solution. K2CuFe(CN)6 homogeneously precipitates on the pore walls of the foam and into the mesoporous network. Exploiting kinetic and adsorption isotherms in various solutions (deionized water, fresh water and fresh water with excess of sodium), a comparative study between the GF and FGF was undertaken. In presence of competitive ions into the solution, the capacity of both materials decreases with respect to the deionized water. The mechanism of exchange is Na+ ↔ Cs+ and K+ ↔ Cs+ for GF and FGF respectively. Although the GF material presents some very high performances in term of ion exchange, in excess of sodium ions, the GF material completely loses its capacity with respect to the FGF that remains constant up to 1 mol/l−1. FGF is therefore very selective with regard to the cesium if other cations coexist into the solution. This is also confirmed by experiments performed in radioactive environment for very low concentration of radioactive cesium where the distribution coefficient (Kd) for the FGF reaches in average 3.5 105 ml g−1 that is ten times higher than for the GF material.

In-situ grown of polyaniline on defective mesoporous carbon as a high performance supercapacitor electrode material

Abstract Herein, the preparation of a nanocomposite based on a defective mesoporous carbon (DMC) and polyaniline (PANI) as an efficient electrode material for the supercapacitor application is reported. DMC, with the interconnected porous network, was synthesized through a facile process using sucrose, commercial nanoparticles of SiO2 and KNO3 as carbon precursor, hard template and defect generating agent respectively. DMC/PANI nanocomposite was produced via an in-situ polymerization of aniline in the presence of DMC. The preparation of PANI in the porous matrix of DMC was proved using different structural analyses including FT-IR, Nitrogen adsorption/desorption, SEM and TEM. The supercapacitive performance of the obtained nanocomposite (DMC/PANI) was evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCD) techniques applying 1 M H2SO4 as electrolyte. Compared to DMC and pure PANI, the DMC/PANI delivered the highest specific capacitance reaching to 985 F g−1 at the applied current density of 0.5 A g−1. Even at high charge/discharge rate of 10 A g−1, the excellent specific capacitance of 780 F g−1 was achieved. Moreover, DMC/PANI composite exhibited long term cyclability, in where 82% of specific capacitance was retained after 5000 GCD measurement at high current density of 5 A g−1. Further, a symmetric supercapacitor device based on DMC/PANI was successfully assembled and specific energy of 32 Wh kg−1 at specific power of 125 W kg−1 was obtained. The presented results are higher or comparable to the earlier reported works based on carbon/PANI composite.

Facile synthesis of graphene-like carbon-coated Ni3S2 nanoparticles self-assembled on 3D dendritic nanostructure as high-performance anode materials of sodium-ion batteries

Although sodium-ion battery is promising to be an alternative to current lithium-ion batteries, it is still facing many challenges and depends on the innovation of the high-performance electrode materials. At present, limited candidates can meet the expectations of high-rate capability, high specific capacity, and long cycle stability simultaneously. Herein, Ni3S2 nanoparticles uniformly embedded in graphene-like carbon layer (Ni3S2/C) self-assembled on three-dimensional (3D) dendritic nanostructure were successfully synthesized with thiourea as sulfur source and ionic liquid as carbon precursor through a simple one-step solid phase calcine strategy. When used as anode material for SIBs, Ni3S2/C nanocomposites afford a high specific capacity of 434.4 mAh g−1 at 0.1 A g−1, excellent rate capability of 277.6 mAh g−1 at current density of 3.0 A g−1, and great cycling stability with a capacity well-maintained to 172.6 mAh g−1 after 200 cycles at 0.1 A g−1. Exceptional cycling capabilities and rate performances could be ascribed to the synergistic effect between graphene-like carbon-coated Ni3S2 nanoparticles and 3D dendritic nanostructure. The unique 3D dendritic nanostructure consists of interconnected porous carbon network, which increases contact between electrode and electrolyte and accelerates the electron transport and ionic diffusion during the discharge-charge process. Furthermore, the graphite-like carbon layer effectively alleviates volume changes and guaranteed structural integrity of Ni3S2 nanoparticles during Na ion insertion and extraction from active material. The kinetic analysis shows that the total charge comes from the contribution of both surface capacitive effect and diffusion-controlled intercalation.

3D printing of metal-organic frameworks decorated hierarchical porous ceramics for high-efficiency catalytic degradation

Combination of porous catalyst carriers and high-performance catalysts has attracted increasing attention due to their efficient, reusable and durable characteristics in water purification. Herein, we report a design of three dimensional printed hierarchical porous ceramics that can in-situ load metal-organic frameworks-based catalysts by facile hydrothermal treatment. The resultant supported catalysts with hierarchical features are capable to completely decompose organic dyes based on Fenton reaction, exhibiting the highest removal efficiency and dye degradation rate (kobs) of 99.68% and 0.2915 min−1, respectively. Moreover, its catalytic degradation rates are much greater than other reported Fe-/Cu-based metal organic framework heterogeneous Fenton catalysts. The outstanding catalytic degradation performance towards organic dyes is ascribed to their large surface area, numerous active sites, and hierarchical matter transport channels in the interconnected porous networks. Also, the three-dimensional (3D) printed hierarchical porous catalysts demonstrate lasting degradation efficiency (>75%) over 50 reusable cycles. More importantly, two types of catalytic reactors, such as 3D-printed catalytic filter and impeller agitator, have been successfully manufactured by the present strategy. This work uncovers a novel strategy that not only enables complex and efficient multiscale porous 3D catalysts, but also presents considerable prospects in the aspects of functional devices for water treatment.

Nitrogen-Doped Hierarchical Porous Carbon Derived from Bacterial Cellulose-Polyaniline Composite As High Performance Anode for Lithium-Ion Batteries

An ever increasing demand for high energy and high power rating Lithium-ion batteries (LIB) for electric hybrid vehicles persuaded the development of novel electrode materials with large storage capability and faster kinetic process. Carbon nanomaterials, owing to their unique and tunable physical and chemical properties, have been widely investigated as anode materials for LIBs. Diversified strategies involving the synthesis of carbon materials with hierarchical structures (morphology and porosity), and heteroatom doping have shown significant improvement in electrochemical performance of these carbon nanomaterials. In consideration to this, we hereby demonstrate the synthesis and utilization of hierarchical nitrogen-doped porous carbon structures derived from bacterial cellulose-polyaniline nano-composites as a promising anode material for LIBs. Microstructural analysis of the derived carbon revealed the inheritance of fibrous backbone as obtained from bacterial cellulose along with nano-granular structure of polyaniline. The structural and electrochemical properties of as-derived porous carbon structures are analysed systematically by performing XRD, Raman spectroscopy, XPS, cyclic voltammetry, galvanostatic charge/discharge studies and impedance spectroscopy. These results unveiled significantly large reversible capacities of 432, 233, and 127 mAh/g at 1, 5, and 10 C-rate respectively with excellent capacity retention. The energy and power densities of these hierarchical porous carbon structures were increased by 54% and 41% respectively when compared to pure bacterial cellulose derived carbon. This enhanced electrochemical performance may be attributed to the combined effect of interconnected micro-meso porous network of hard carbon along with nitrogen doping. The core-shell structure of this derived carbon accommodates the volume changes during lithium-ion insertion and de-insertion, rendering excellent cyclic stability even at high C rates without causing pulverization.

Injection Molding of 3-3 Hydroxyapatite Composites.

The manufacturing of ideal implants requires fabrication processes enabling an adjustment of the shape, porosity and pore sizes to the patient-specific defect. To meet these criteria novel porous hydroxyapatite (HAp) implants were manufactured by combining ceramic injection molding (CIM) with sacrificial templating. Varied amounts (Φ = 0–40 Vol%) of spherical pore formers with a size of 20 µm were added to a HAp-feedstock to generate well-defined porosities of 11.2–45.2 Vol% after thermal debinding and sintering. At pore former contents Φ ≥ 30 Vol% interconnected pore networks were formed. The investigated Young’s modulus and flexural strength decreased with increasing pore former content from 97.3 to 29.1 GPa and 69.0 to 13.0 MPa, agreeing well with a fitted power-law approach. Additionally, interpenetrating HAp/polymer composites were manufactured by infiltrating and afterwards curing of an urethane dimethacrylate-based (UDMA) monomer solution into the porous HAp ceramic preforms. The obtained stiffness (32–46 GPa) and Vickers hardness (1.2–2.1 GPa) of the HAp/UDMA composites were comparable to natural dentin, enamel and other polymer infiltrated ceramic network (PICN) materials. The combination of CIM and sacrificial templating facilitates a near-net shape manufacturing of complex shaped bone and dental implants, whose properties can be directly tailored by the amount, shape and size of the pore formers.

3D Printing of Piezoelectric Barium Titanate-Hydroxyapatite Scaffolds with Interconnected Porosity for Bone Tissue Engineering.

The prevalence of large bone defects is still a major problem in surgical clinics. It is, thus, not a surprise that bone-related research, especially in the field of bone tissue engineering, is a major issue in medical research. Researchers worldwide are searching for the missing link in engineering bone graft materials that mimic bones, and foster osteogenesis and bone remodeling. One approach is the combination of additive manufacturing technology with smart and additionally electrically active biomaterials. In this study, we performed a three-dimensional (3D) printing process to fabricate piezoelectric, porous barium titanate (BaTiO3) and hydroxyapatite (HA) composite scaffolds. The printed scaffolds indicate good cytocompatibility and cell attachment as well as bone mimicking piezoelectric properties with a piezoelectric constant of 3 pC/N. This work represents a promising first approach to creating an implant material with improved bone regenerating potential, in combination with an interconnected porous network and a microporosity, known to enhance bone growth and vascularization.

Solvent‐Free Chemical Approach to Synthesize Co Nanoparticles Supported on N‐doped Porous Carbon for Efficient Electrocatalytic Oxygen Reduction

AbstractTransition metal/N‐doped carbon materials are the most promising alternative to expensive Pt‐based electrocatalysts for oxygen reduction reaction (ORR). In this paper, we design hierarchical three‐dimensional (3D) Co nanoparticles supported on N‐doped carbon (Co/N−C) with abundant defects using a simple solvent‐free strategy. With the help of templates, Co nanoparticles are embedded in the interconnected porous carbon network derived from phenolic resin, and Co/N−C is obtained after the introduction of N atoms. Benefitting from the coupling effect of Co and N in carbon matrix, Co/N−C exhibits better electrocatalytic performance than porous N‐doped carbon (N−C) for ORR in alkaline medium. The Co/N−C shows a dominant four‐electron transfer toward oxygen reduction with a rather high half‐wave potential of 0.82 V versus relative hydrogen electrode (vs. RHE), as well as good stability and methanol tolerance. The crumpled porous 3D structure of Co/N−C with a high specific surface area facilitates the formation of N‐contained defects as active sites, and boosts the transport of electrons and ions. Our work provides a feasible way to design non‐noble metal electrocatalysts with satisfied properties for ORR.

Biochar-based composites as electrode active materials in hybrid supercapacitors with particular focus on surface topography and morphology

Abstract The development of biochar-based composites from biomass and the prospect of developing carbon-based electrodes have attracted considerable attention within the electrochemistry community. Although functional carbon-based materials (e.g. activated carbon, carbon nanotubes/fibers, and graphene) are conventionally used as an electrode in energy storage systems due to their low potential plateau, acceptable capacity, and stable cycling performance, there still are significant disadvantages associated with these materials reliance on fossil fuels and energy-intensive synthesis conditions which make them environmentally harmful and costly. Hence, the conversion of biomass into biochar-based composites with desirable structure (i.e. heteroatom doped, hierarchical porous, interconnected 3D pore network, few-layer graphene, few-walled carbon nanotubes (CNTs), and olive and circular-shaped structures) has recently been introduced as an alternative to conventional electrode active material and successfully enhanced the energy content and mitigated waste management issues. Herein we review and summarize the various physical and chemical modifications for biochar-based composites and compare their electrochemical behaviors in energy storage systems. To the authors' knowledge, there is presently no available literature that concisely summarizes the surface topography and morphology on nitrogen-based 3D interconnected composites.

In situ observation of the percolation threshold in multiphase magma analogues

Magmas vesiculate during ascent, producing complex interconnected pore networks, which can act as outgassing pathways and then deflate or compact to volcanic plugs. Similarly, in-conduit fragmentation events during dome-forming eruptions create open systems transiently, before welding causes pore sealing. The percolation threshold is the first-order transition between closed- and open-system degassing dynamics. Here, we use time-resolved, synchrotron-source X-ray tomography to image synthetic magmas that go through cycles of opening and closing, to constrain the percolation threshold ΦC at a range of melt crystallinity, viscosity and overpressure pertinent to shallow magma ascent. During vesiculation, we observed different percolative regimes for the same initial bulk crystallinity depending on melt viscosity and gas overpressure. At high viscosity (> 106 Pa s) and high overpressure (~ 1–4 MPa), we found that a brittle-viscous regime dominates in which brittle rupture allows system-spanning coalescence at a low percolation threshold (ΦC~0.17) via the formation of fracture-like bubble chains. Percolation was followed by outgassing and bubble collapse causing densification and isolation of the bubble network, resulting in a hysteresis in the evolution of connectivity with porosity. At low melt viscosity and overpressure, we observed a viscous regime with much higher percolation threshold (ΦC > 0.37) due to spherical bubble growth and lower degree of crystal connection. Finally, our results also show that sintering of crystal-free and crystal-bearing magma analogues is characterised by low percolation thresholds (ΦC = 0.04 – 0.10). We conclude that the presence of crystals lowers the percolation threshold during vesiculation and may promote outgassing in shallow, crystal-rich magma at initial stages of Vulcanian and Strombolian eruptions.

A p-tert-Tutyldihomooxacalix[4]arene Based Soft Gel for Sustained Drug Release in Water.

P-tert-butyldihomooxacalix[4]arene is a well-known calix[4]arene analog in which one CH2 bridge is replaced by one -CH2OCH2- group. Thus, dihomooxacalix[4]arene has a slightly larger cavity than that of calix[4]arene and usually possesses a more flexible cone conformation, and the bridged oxygen atom might provide additional binding sites. Here, we synthesized a new functional p-tert-butyldihomooxacalix[4]arene 1 through Ugi reaction with good yield (70%), starting from condensed p-tert-butyldihomooxacalix[4]arene O-alkoxy–substituted benzaldehydes, benzoic acid, benzylamine, and cyclohexyl isocyanide. Proton nuclear magnetic resonance spectroscopy (1H NMR), 13C NMR, IR, and diffusion-ordered 1H NMR spectroscopy (DOSY) methods were used to characterize the structure of 1. Then soft gel was prepared by adding 1 into cyclohexane directly. It shows remarkable thermoreversibility and can be demonstrated for several cycles. As is revealed by scanning electron microscopy (SEM) images, xerogel showed highly interconnected and homogeneous porous network structures, and hence, the gel is suitable for storage and controlled release.

Vertically Aligned Metal-Organic Framework Derived from Sacrificial Cobalt Nanowire Template Interconnected with Nickel Foam Supported Selenite Network as an Integrated 3D Electrode for Overall Water Splitting.

The development of bifunctional, highly active electrocatalysts for an overall water splitting reaction remains a major challenge. Here, the sacrificial template-assisted transformation of cobalt hydroxide nanowire (Co(OH)2 NW) into a metal-organic framework network (MOF) is conceived as a porous structure that provides extremely active and durable electrochemical energy conversion characteristics. After this, the 1D MOF modified Co NWs can be further transformed into a hybrid structure (MOF CoSeO3 NWs) by selenization. The self-template transformation strategy allows the interconnected porous conductive network to be exposed to abundant reactive sites and to improve electronic conductivity/structural integrity. Thus, the obtained catalyst established by electrocatalytic activity in the course of the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in 1 M KOH solution requires overpotentials (η) of 290 and 150 mV to achieve a current density of 50 and 10 mA cm-2 for both OER and HER. Interestingly, as a full cell water electrolyzer (MOF CoSeO3 NWs (+) // MOF CoSeO3 NWs (-)), the MOF CoSeO3 NW's modified electrode exhibits an affordable cell voltage of 1.675 V at a current density of 100 mA cm-2. This work involves a viable and systematic strategy to prepare many other functional integrated MOFs that can be used for energy storage and conversion in multiple applications.

Solvent‐Free Generation of Foamed Microcapillary Films with a Dual Network of Interconnected Pores and Internal Channels

AbstractA dual‐pore network is favored in applications such as tissue engineering scaffolds. In this paper, foamed microcapillary films (FMCFs) are prepared based on a poly(lactic acid)/poly(butylene succinate) blend using melt extrusion and batch foaming with supercritical carbon dioxide. Such films are characterized by multiple hollow microcapillaries (diameter of 100–360 µm) connected with cells (size of 3–194 µm, open‐cell content of over 80%) within the scaffold. By plugging the ends of the MCF before foaming, the formation of a solid skin layer is successfully avoided. Furthermore, the diameter of the microcapillaries of an FMCF can be adjusted using the designed foaming strategy. The effects of the foaming condition on the FMCF foaming behavior are also investigated. When other conditions are fixed, the foaming behavior changes dramatically when the foaming temperature changes within the range of 120–123 °C.