Hybrid Porous Structures Research Articles

3D Printed P(VdF‐HFP)/SBA‐15 composite‐based gel polymer electrolyte versus commercial celgard: A comparative investigation on thermal stability and electrochemical performance for lithium‐ion battery application

AbstractThe current work reports on tailoring of 3D printed gel polymer electrolyte (GPE) employing poly(vinylidene fluoride‐co‐hexafluoropropylene) P(VdF‐HFP) as the host matrix and mesoporous Santa Barbara Amorphous‐15 (SBA‐15) mesoporous sieve as ceramic filler. Further, this work envisages an investigation on its physicochemical properties, thermal shrinkage behavior, and electrochemical performance. An effort has been undertaken to formulate 3D printable P(VdF‐HFP)/SBA‐15 composite‐based GPE ink with suitable rheological properties. The breath figure method is followed to investigate the influence of 1‐methyl‐2‐pyrrolidinone (NMP)/tetrahydrofuran (THF) mixture as a solvent on the porosity of 3D printed GPE, through which enhanced porosity is evident from scanning electron microscopy (SEM) analysis. The morphological analysis further confirms the hybrid porous structure facilitated by the addition of SBA‐15 into the P(VdF‐HFP) matrix. The 3D printed P(VdF‐HFP)/SBA‐15 (10%) composite‐based GPE shows promising ionic conductivity in the order of 0.2 × 10−4 S/cm at room temperature and demonstrates excellent dimensional thermal stability up to 175°C. The electrochemical measurement of 3D printed GPE is tested separately using 3D printed cathode half‐cell (3D printed LFP vs. Li+) and 3D printed anode half cell (3D printed LTO vs. Li+) with GPE as separator. Further, also tested with conventionally prepared electrode and the coin cell studies show discharge capacity of 3D printed P(VdF‐HFP)/SBA‐15 (10%) composite‐based GPE is comparable to commercial celgard separator. All these features speculate that the 3D printed fabricated in the current work may find potential application in lithium‐ion battery.

Multiphase flow simulation in hybrid porous structure

Recent research has primarily focused on creating biporous and hybrid porous structures with multiple pore sizes and length scales to optimize capillary pressure and permeability. Despite numerous experimental investigations on biporous and hybrid media, there is a noticeable absence of numerical simulations that explore the multiphase flow within these media. Therefore, the present study aims to conduct a pore-scale numerical simulation of two-phase flow in a biporous structure. The biporous structure is proposed by arranging clusters of solid particles in a staggered regular pattern, with each cluster consisting of closely packed particles. The dimensions and characteristics of the simulated structure are based on previous experimental literature on biporous and hybrid media. A monoporous structure simulation is also included for comparison with biporous results. ANSYS Fluent is utilized to carry out the numerical simulations of capillary pumping flow. The simulation results indicate that the permeability and average capillary pressure of the biporous media are four times and over one and a half times higher, respectively, compared to those of the monoporous media. The presence of smaller pathways within each cluster of a biporous and hybrid porous media enhances the capillary effect in comparison to conventional monoporous structures. Additionally, the larger pores between the clusters contribute to a higher permeability of the hybrid porous structure. As a result, the combined effect of increased capillary action and higher permeability leads to improved performance of the hybrid porous structure. Overall, the proposed simplified biporous geometry accurately models fluid flow in real, complex biporous and hybrid structures.

Effect of Polyhydroxyalkanoate (PHA) Concentration on Polymeric Scaffolds Based on Blends of Poly-L-Lactic Acid (PLLA) and PHA Prepared via Thermally Induced Phase Separation (TIPS)

Hybrid porous scaffolds composed of both natural and synthetic biopolymers have demonstrated significant improvements in the tissue engineering field. This study investigates for the first time the fabrication route and characterization of poly-L-lactic acid scaffolds blended with polyhydroxyalkanoate up to 30 wt%. The hybrid scaffolds were prepared by a thermally induced phase separation method starting from ternary solutions. The microstructure of the hybrid porous structures was analyzed by scanning electron microscopy and related to the blend composition. The porosity and the wettability of the scaffolds were evaluated through gravimetric and water contact angle measurements, respectively. The scaffolds were also characterized in terms of the surface chemical properties via Fourier transform infrared spectroscopy in attenuated total reflectance. The mechanical properties were analyzed through tensile tests, while the crystallinity of the PLLA/PHA scaffolds was investigated by differential scanning calorimetry and X-ray diffraction.

Co/Co-N/Co-O Rooted on rGO Hybrid BCN Nanotube Arrays as Efficient Oxygen Electrocatalyst for Zn-Air Batteries.

Developing high-performance non-noble metal bifunctional oxygen reduction and evolution reaction electrocatalysts is a critical factor for the commercialization of rechargeable Zn-air batteries. Herein, Co/Co-N/Co-O rooted on reduced graphene oxide (rGO) hybrid boron and nitrogen codoped carbon (BCN) nanotube arrays (BCN/rGO-Co) is prepared by facile low-temperature precross-linking and high-temperature pyrolysis treatment. Benefit from the synergistic effect of its B/N codoping, Co/Co-N/Co-O bifunctional active sites, 3D hybrid porous structure of BCN nanotubes, and highly conductive rGO sheets. The obtained BCN/rGO-Co exhibits superior bifunctional oxygen catalytic activity with a positive ORR half-wave potential (0.85 V) and a low OER potential (1.61 V) at 10 mA cm-2. Additionally, the BCN/rGO-Co-based liquid Zn-air batteries displays a large peak power density of 157 mW cm-2, and a long charge/discharge cycle stability of 200 h, outdoing the commercial Pt/C+Ru/C catalyst.

Fabrication of light‐weight ultrahigh molecular weight polyethylene films with hybrid porous structure and the thermal insulation properties

AbstractAccording to the infrared stealth mechanism, controlling the surface temperature of objects can effectively hide the infrared radiation and resist the infrared detection. In this paper, a high infrared transparent polymer ultrahigh molecular weight polyethylene (UHMWPE) is selected as the matrix of a thermal insulation material. UHMWPE porous films with high porosity and hybrid pore structure are obtained through the thermal induced phase separation combining with particle leaching method. The film structures with micropores and macropores are adjusted through the variation of the mass ratio of UHMWPE/liquid paraffin, the dosage and the particle size of NaCl. The thermal conductivity of the UHMWPE film is as low as 0.034 W/(m K), while the density is only 54.4 mg/cm3. The classical Maxwell‐Eucken model is used to discuss the relationship between the pore structure and the thermal conductivity of the films. It is determined that the hybrid porous structure can reduce heat conduction and gas–solid coupling effect simultaneously, thus the thermal conductivity is significantly reduced. Moreover, the porous films exhibited remarkable flexibility and hydrophobicity. Based on these properties, the porous films are highly promising in the field of thermal insulation protection and infrared stealth.

Construction of ternary (1D/2D/3D) Fe2O3-supported micro pillared Cu-based MOF on chitosan with improved photocatalytic behavior on removal of paraquat.

A hetero-structured metal organic framework of Cu-BTC and Fe2O3 nano-photocatalyst were tethered over chitosan using the hydrothermal method and fabricated a hybrid porous nanocomposite (CS-Fe@Cu-BTC). X-ray diffractometer results exposed the existence of Fe2O3 peaks. Surface area measurements using BET showed a mesoporous structure and the formation of type IV adsorption isotherm for nanocomposite. XPS and SEM-EDAX confirmed the existence of Fe2O3 nanoparticles in the hybrid porous structure. The UV-vis diffuse reflectance absorption shape emphasized the role of Fe2O3 in enhancing the band gap of CS-Fe@Cu-BTC nanohybrid. The lower intensity photoluminescence spectra of the CS-Fe@Cu-BTC shows a competent charge partition and delayed the recombination of electron-hole pairs. The photo-mineralization efficiency of Cu-BTC and CS-Fe@Cu-BTC was evaluated in terms of electronic interactions using paraquat (PQT) as the probe molecule, which shows a mineralization of 91% at the pH range of ~ 5. The contribution of •OH in the degradation of PQT over CS-Fe@Cu-BTC nanocomposites revealed using the trapping test and the degradation mechanism follows the Langmuir-Hinshelwood model and pseudo-first-order kinetics. The durability of the CS-Fe@Cu-BTC nanocomposite was also established after four cycling processes.

NiCo2O4 nanoneedle-nanosheet hybrid structure on CC substrate for high-performance flexible supercapacitors

In this paper, three different morphologies of NiCo2O4 nanoarrays, namely, nanosheet (S-NiCo2O4), nanoneedle (N-NiCo2O4) and their hybrid nanostructure (M-NiCo2O4) were successfully prepared on flexible carbon cloth (CC) by a hydrothermal method. The structures, surface morphologies and compositions of the samples were respectively characterized by XRD, SEM, EDS, and XPS, and the effect of NiCo2O4 morphologies on the electrochemical performances was systematically investigated. It is found that the M-NiCo2O4/CC electrode demonstrates the best supercapacitive performance among the three kinds of samples, typically its specific capacitance is 1347.4 F/g at 1 A/g (1509.1 F/cm2 at 1 mA/cm2), much higher than that of S-NiCo2O4 (938.4 F/g at 1 A/g) and N-NiCo2O4 (1022.4 F/g at 1 A/g). Meanwhile, the M-NiCo2O4/CC sample exhibits excellent rate capability (81.6%, from 1 A/g to 15 A/g) and cycling stability (92.4% retention after 10,000 cycles). In addition, an flexible solid-state asymmetric supercapacitor (ASC) with M-NiCo2O4/CC as positive electrode manifests great capacity retention (94% after 5000 cycles) and outstanding energy density of 41.7 Wh/kg at the power density of 750 W/kg. Moreover, the charge-discharge time shows no significant change after 2000 bends, demonstrating its application potential in the field of flexible SCs. The excellent performance is attributed to the unique hybrid porous structure of one-dimensional (1D) nanoneedles and two-dimensional (2D) nanosheets.

Sp2–sp3 Hybrid Porous Carbon Materials Applied for Supercapacitors

Carbon materials have gained considerable attention in recent years due to their superior properties. Activated carbon has been used in supercapacitors due to its density and rapid adsorption capability. The sp2–sp3 hybrid porous carbon materials are synthesized using herringbone-type carbon nanofibers (CNFs) and carbonized spherical phenol resins, with KOH as the activating agent. The morphology of the hybrid porous carbon facilitates the formation of ribbon-like nanosheets from highly activated CNFs wrapped around spherical resin-based activated carbon. The etching and separation of the CNFs produce a thin ribbon-like nanosheet structure; these CNFs simultaneously form new bonds with activated carbon, forming the sp2–sp3 hybrid porous structure. The relatively poor electrical conductivity of amorphous carbon is improved by the 3D conductive network that interconnects the CNF and amorphous carbon without requiring additional conductive material. The composite electrode has high electron conductivity and a large surface area with a specific capacitance of 120 F g−1. Thus, the strategy substantially simplifies the hybrid materials of sp2-hybridized CNFs and sp3-hybridized amorphous spherical carbon and significantly improves the comprehensive electrochemical performance of supercapacitors. The developed synthesis strategy provides important insights into the design and fabrication of carbon nanostructures that can be potentially applied as electrode materials for supercapacitors.

Ultra-high molecular weight polyethylene with hybrid porous structure

A novel method of a hybrid porous structure preparation in UHMWPE was developed. A porous structure consisted of large 50–900 μm and medium-size 50 nm-4 μm macropores together with mesopores. The polymodal structure was prepared via water leaching of UHMWPE-NaCl composite followed by o-xylene treatment at a temperature of 99–103 °C with further supercritical drying in CO2. Scanning electron micrograph showed the formation of additional porous structure on the large macropores’ walls surface formed by lamellar crystals. The size and quantity of the lamellar crystals depended on the heating temperature and could be varied over a wide range. The formation of the hybrid porous structure in UHMWPE was accompanied by a significant increase in the crystallinity degree (up to 81%) and specific surface area (up to 65 m2/g). The mechanical behavior of the UHMWPE with hybrid porous structure was investigated by DMA. The change in the UHMWPE crystal structure led to a change in the UHMWPE relaxation behavior and to an increase of damping ability.

Metal–Organic Framework (MOF) through the Lens of Molecular Dynamics Simulation: Current Status and Future Perspective

As hybrid porous structures with outstanding properties, metal–organic frameworks (MOFs) have entered into a large variety of industrial applications in recent years. As a result of their specific structure, that includes metal ions and organic linkers, MOFs have remarkable and tunable properties, such as a high specific surface area, excellent storage capacity, and surface modification possibility, making them appropriate for many industries like sensors, pharmacies, water treatment, energy storage, and ion transportation. Although the volume of experimental research on the properties and performance of MOFs has multiplied over a short period of time, exploring these structures from a theoretical perspective such as via molecular dynamics simulation (MD) requires a more in-depth focus. The ability to identify and demonstrate molecular interactions between MOFs and host materials in which they are incorporates is of prime importance in developing next generations of these hybrid structures. Therefore, in the present article, we have presented a brief overview of the different MOFs’ properties and applications from the most recent MD-based studies and have provided a perspective on the future developments of MOFs from the MD viewpoint.

AC characterization of three-dimensional reduced graphene oxide/molybdenum disulfide nanorose hybrids for ethanol vapor detection

A novel AC impedance study on three-dimensional hybrid structures of graphene sheets/MoS2 nanorose (GMS) toward ethanol vapor detection is presented in this work. These defective 3D hybrid porous structures are sensitive to the presence of different gases as a result of charge transfer with gas species, as well as a change in the effective capacitance of the system. The sensing behavior of the samples is investigated throughout time-dependent impedance measurement and electrochemical impedance spectroscopy (EIS). The sensor response is estimated at about 20% to 10 ppm ethanol vapor, with the response and recovery times about 3.2 s and 0.8 s, respectively. Sensing mechanism proposed to describe the EIS impedance spectra involves three different procedures: charge transfer, double layer formation and diffusion process. Moreover, these processes are probed using equivalent circuits modeled by the impedance spectra curves.

Facile self-assembling of three-dimensional graphene/solvent free carbon nanotubes fluid framework for high performance supercapacitors

Carbon based electrode materials, such as carbon nanotubes (CNTs) and graphene, exhibit an excellent potential for supercapacitor electrodes. Morphology control is an effective approach to create the abundant ion paths and highly porous structures of carbon materials. In this study, solvent-free CNTs fluid (CNTF) and graphene oxide (GO) were used to establish a facile fabrication of porous three-dimensional (3D) CNTs/graphene hybrid porous structures using a one-step self-assembly hydrothermal method. CNTF is hydrophilic and can form a homogeneous CNTF/GO aqueous solution. Moreover, CNTF acts as a cross-linker and spacer to connect adjacent graphene sheets and prevent the restacking of graphene. The unique 3D CNTF/RGO composite electrode exhibits a high specific capacitance of up to 412.8 F/g at a current density of 1 A/g; further, it displays a specific capacitance of 137.3 F/g even at a high discharge rate of 10 A/g. The specific capacitance remains at 89.6% of the initial value after 10,000 charging/discharging cycles. This solvent-free fluid technique has been achieved with the direct self-assembly of 3D CNTs/graphene materials in water and can be utilized in broad applications that are potentially feasible for other 3D carbon materials.

Metal Organic Framework (MOF)-Derived carbon-encapsulated cuprous sulfide cathode based on displacement reaction for Hybrid Mg2+/Li+ batteries

We fabricate in-situ carbon-encapsulated cuprous sulfide (Cu2S@C) composite through a metal-organic framework (MOF)-derived sulfurization method and compare its electrochemical performance as a displacement reaction cathode of hybrid Mg2+/Li+ batteries with 0.4 mol L−1 (PhMgCl)2-AlCl3+1.0 mol L−1 LiCl/THF nucleophilic hybrid electrolyte and 0.2 mol L−1 Mg(HMDS)2-(AlCl3)2–MgCl2+1.0 mol L−1 LiTFSI/DME non-nucleophilic hybrid electrolyte. Benefiting from the intrinsic property of Cu2S, well-defined hybrid porous structure and carbon encapsulation derived from MOFs, the Cu2S@C composite exhibits 399.2 mA h g−1 discharge capacity and the capacity maintains at approximately 150 mA h g−1 at 0.05 C after 50 cycles in the nucleophilic hybrid electrolyte. The mechanism investigation verifies that the formed Cu1.96S in the first discharge process succeeds to transform into MgS and Li2S, which results in the reversible displacement reaction dominantly occurring between Cu1.96S and Cu during subsequent cycles. When using the non-nucleophilic hybrid electrolyte, an enhanced cycling stability can be achieved due to the mitigation of ionic sulfide dissolution. The present work demonstrates the feasibility of building the structural design of low-cost displacement reaction cathode with more compatible electrolyte, and provides the potential of establishing practical hybrid Mg2+/Li+ batteries for energy storage.

Efficient photoactivity of TiO2-hybrid-porous nanocomposite: Effect of humidity

TiO2 photocatalyst and Cu-BTC metal organic framework were successfully coupled via sol-gel method to form a hybrid porous nanocomposite (TiO2-hybrid-PNC). X-ray diffraction (XRD) results revealed the intense characteristic TiO2 anatase peaks. Surface area (BET) measurements showed type IV adsorption isotherm with the formation of a mesoporous structure for TiO2-hybrid-PNC. Scanning electron microscopy elemental analysis-mapping images (SEM-EDX) and X-ray photoelectron spectra (XPS) confirmed the existence of TiO2 nanoparticles in the hybrid porous structure. UV–Vis diffuse reflectance (UV–Vis DRS) absorption profile of TiO2-hybrid-PNC had impacts from both TiO2 and Cu-BTC. The lower photoluminescence (PL) intensity of TiO2-hybrid-PNC possessed an efficient charge separation and inhibited electron-hole recombination compared to the Cu-BTC. Dark absorption capacities and photoactivities of Cu-BTC and TiO2-hybrid-PNC were discussed in terms of electronic interactions using methyl orange (MO) as probe molecule. Effect of humidity on the dark abilities and photocatalytic performances of Cu-BTC and TiO2-hybrid-PNC was investigated after their exposure to 40%, 67% and 84% relative humidity (RH) values. According to XRD and SEM analysis, structural features of TiO2-hybrid-PNC were preserved under humid conditions. Photocatalytic efficiency of TiO2-hybrid-PNC enhanced with increments in RH percentages owing to the formation of more hydroxyl radicals. TiO2-hybrid-PNC (84% RH) revealed a higher rate constant than that of TiO2-hybrid-PNC based on pseudo-first order kinetics and Langmuir-Hinshelwood model. Durabilities of TiO2-hybrid-PNC and TiO2-hybrid-PNC (84% RH) were also confirmed after four cycling experiments.

Research on the Preparation of Polycaprolactone Porous Films with Decoration of Protein Arrays via the Emulsion‐Based Breath Figure Method

AbstractA facile method to fabricate honeycomb‐patterned biocompatible polycaprolactone (PCL) films with cavities that are selectively decorated with protein by one‐step method is developed in this study. To carry out this method, proteins carried in water are dispersed into chloroform solution of PCL to form inverse emulsion with the assistance of the chitosan particles serving as emulsifier. The evaporation of the organic solvent in the inverse emulsion on substrate under a high‐humidity atmosphere leads to the formation of ordered porous arrays incorporated with proteins on the inner surface of the cavities. The method, based on the combination of breath figures and inverse emulsion template, provides a reliable route for the directed assembly of water‐soluble materials into patterned polymer matrix. It has the potential to be further established as a novel procedure to fabricate a multifunctional hybrid porous structure containing hydrophilic component based on the breath figure method.

Tin Oxides with Nano and Micron-Sized Pores for Functional Electrochemical Devices

Metal oxides with one-dimensional (1-D) nano-channels have drawn much attention as potential electrode materials for high performance functional electrochemical devices. This is mainly because the large surface area of nanostructures and the 1-D pathway of reactants/products in channels result in low activation and concentration polarizations, respectively. In spite of such advantages, the expected high rate and high efficient operation of the devices adopting the electrodes with nano-channeled structure might not be quite sustainable particularly when the rate of surface reaction far exceeds that of mass transport through the channels. That is, the reactants/products would be seriously depleted/accumulated in the channel at the very high rate of surface reaction, possibly leading to the significant decrease in total reaction rate. One way to solve this problem is to prepare the hybrid porous structure composed of both nano-sized and micron-sized pores, where the latter efficiently provides the reactants to or receives the products from the nano-channels. It has been known that an anodic oxidation process is a quite effective way to create the metal oxide films with well-defined 1-D nano-channeled structure. Among the anodic metal oxides with 1-D structure, tin oxide is worthy of attention due to its widespread use in various applications, such as catalysis, gas sensing and energy storage. In this work, meso- and macro- hybrid porous structure is created without a template by an anodic oxidation process. From the experimental results, it is suggested that the substrate, the anodizing time, the thickness of the pre-anodized tin have an important effect on the size and density of macro-pores in hybrid porous structure. For example, the well-defined meso/macro hybrid porous tin oxides can be created when silicon was used as a substrate to anodize tin thin film. On the basis of the mechanical analysis of the different substrates and different thicknesses of tin film on them, it is suggested that the substrate with high elastic modulus might result in high compressive stress to the anodic tin oxide and generate local cracks in the initial stage of anodizing process, which grow to macro-pores with semispherical shape in the later stage. From two step anodizing process including the intervening selective etching of tin oxide, highly-open meso/macro hybrid porous tin oxide is successfully prepared. Anodic tin oxide formed under the macro-pores has meso-porous structure with radial shape, ideally suited for high rate and high efficient functional electrochemical devices.

Evolution of porous structure with dealloying corrosion on Gasar Cu–Mn alloy

The evolution of nanoporous structure with dealloying condition was investigated, thus, the mechanism of porous structure evolution was uncovered. The Gasar Cu–Mn alloy was dealloyed by room and elevated temperature chemical corrosion, low and high current level electrochemical corrosion, four types of porous structures, including uneven corrosion pits, hybrid porous, haystack type and bicontinuous model were prepared by chemically and electrochemically dealloying the porous Cu–34.6%Mn alloy made by the Gasar process. Then, the surface diffusion coefficient (DS) and the diffusion frequency (kD) of Cu atom, as well as the dissolution frequency (kE) of Mn atom were calculated with dealloying condition. The dealloyed morphologies for room temperature chemical corrosion and low current level electrochemical corrosion were similar due to the same DS. While the dealloyed structures changed from bulk hybrid porous structure to bicontinuous porous film with decreasing kD/kE.

Immobilization of laccase on chitosan–halloysite hybrid porous microspheres for phenols removal

In this paper, we used natural resources of halloysite nanotubes and chitosan to prepare new porous organic/inorganic hybrid microspheres with diameter of about 100–150μm by reversed-phase suspension cross-linking technique. The SEM image revealed that halloysite nanotubes overlapped together within hybrid microspheres and formed a hybrid porous structure. We demonstrated that the resulted porous microspheres could be used as a new kind of support to immobilize laccase, which showed excellent loading capacity for laccase immobilization as high as 123.1 mg/g. The stability of laccase was also greatly improved after immobilization on the support. While the immobilized laccase was used as biocatalyst to remove phenols from wastewater, the removal efficiency could reach as high as 95.0%.

Microstructured Nanopore-Walled Porous Silicon as an Anode Material for Rechargeable Lithium Batteries

Porous silicon (PS) with a micro-nano-hybrid structure has been successfully fabricated with an electrochemical etching process. The micropores consist of one-dimensional tunnels, which vary from ca. 1 to in pore diameter and extend up to in depth. The walls of these micropores are covered with a nanoporous structure that consists of small spherical particles, the feature size of which is of the order of tens of nanometers or smaller. The as-prepared PS structures show cathodic/anodic peaks for lithiation/delithiation during cyclic voltammetry with minimal destruction of either the micropore or nanopore of its wall even after 50 cycles. Furthermore, the peak current, the cumulative charge increase, and the electrochemical impedance for electrode reactions consistently decreases with the surface area of the tunnel wall, indicating that processes at the tunnel wall govern the overall lithiation/delithiation reactions. A hybrid porous structure consisting of microtunnels with nanostructured surface layers appears to provide a viable and practical way to utilize silicon for anode materials in rechargeable microbatteries.