Sponge-like Pores Research Articles

Nanofiber-enrich activated carbon coin derived from tofu dregs as electrode materials for supercapacitor

In this study, the activated carbon with enriched nanofiber obtained from free-binder materials. It was conducted tofu dregs carbon nanofiber as electrode material for supercapacitor without the addition of pVdF/PTFE. The chemical impregnation of NaOH, ZnCl2 and H3PO4 at high-temperature pyrolysis in an N2-CO2 environment converted the tofu dregs into carbon coin. Subsequently, the physical properties including, microcrystalline, morphology, element analysis, and electrochemical properties of specific capacitance were investigated. The morphological structure of activated carbon showed high nanofiber density and was decorated by sponge-like pores. In addition, the nanofiber contains oxygen content of 12.70% which can act as self-doping due to the pseudo-capacitance properties. Furthermore, the two-electrode system obtained a specific capacitance of 163 F g-1 in 1 M H2SO4 electrolyte. The results showed that tofu dregs-based activated carbon coins are sustainable and efficient to obtain high-dense nanofiber structure as electrode materials for energy storage applications.

Targeted perfusion adsorption for hyperphosphatemia using mixed matrix microspheres (MMMs) encapsulated NH2-MIL-101(Fe).

Hyperphosphatemia, a common complication of chronic renal failure patients, is described as an excess amount of serum phosphate >4.5 mg dL-1. Current therapy for hyperphosphatemia is limited by low removal efficiency, secondary hyperparathyroidism, uremic bone disease, and the promotion of vascular and visceral calcifications. Metal organic frameworks (MOFs) have aroused great interest in the field of blood purification because of their strong specific adsorption. Herein, we prepared mixed matrix microspheres (MMMs) encapsulated NH2-MIL-101(Fe) with specific adsorption to blood phosphate. Simultaneously, a heparinoid copolymer poly (acrylic acid-sodium 4-vinylbenzenssulfonate) (P(AA-SSNa)) was incorporated to improve the hemocompatibility. The proposed MMMs exhibited excellent phosphate adsorption capacity both in aqueous and human plasma environments. They also showed comprehensive hemocompatibility e.g. low tendency of protein adsorption, low hemolysis rate and extended blood coagulation time. In general, we envision that the MMMs are potentially suitable as highly efficient hemoperfusion adsorbents for hyperphosphatemia treatment.

Photocatalytic antifouling properties of novel PVDF membranes improved by incorporation of SnO2-GO nanocomposite for water treatment

Excellent separation performance and anti-contamination of novel SnO2-graphene oxide/polyvinylidene fluoride (SnO2-GO/PVDF) membranes with complete sponge-like pores were produced by the delay phase conversion method via introducing the nanocomposite (SnO2-GO) into casting solution of PVDF, in which the interconnection of SnO2 and GO was able to improve photocatalysis capacity and entrust modified membranes with self-cleaning capability. The SnO2-GO/PVDF membranes exhibited enhanced effectiveness of photodegradation (increased approximately 60-80%) and superb photodegradation kinetics to bovine serum albumin (BSA) in comparison with modified membranes replenished with GO and SnO2, respectively. Furthermore, the BSA rejection and permeation of SnO2-GO/PVDF membranes were also superior over other check samples on account of the enhanced hydrophilicity, special sponge-like pore structure and photodegradation capacity. Besides, the rejection rate of BSA attached breathtaking 97.2% under high flux (363.2 L m−2 h−1). Hence, the SnO2-GO/PVDF membranes could possess ample potentiality as the younger generation of multifunctional antipollution membranes for water treatment in the foreseeable future.

One-step fabrication of transparent superhydrophobic surface

A self-cleaning, transparent superhydrophobic silica-based surface with water contact angle (CA)/sliding angle (SA) 168°/2° was fabricated by simple one-step thermal oxidation of silicone grease. Microstructural studies (FESEM/TEM) confirmed the presence of a sponge-like pore structure of amorphous silica nanoparticle having a diameter of around 20 ± 2.2 nm. EDS analysis confirms the presence of C, Si, and O in coated substrates. Also, phase and thermal studies (XRD, FTIR, and TG-DSC) analysis showed the thermo-oxidative decomposition of silicone grease results in superhydrophobic –H2C-Si-O-Si-CH2- network structure at 400 °C followed by thermally stable superhydrophilic HO-Si-O-Si-OH network structure at 500 °C. The coated surface showed excellent stability towards corrosive liquids (1 M NaCl, NaOH, HCl aqueous solution, and hot water) and exposed temperature up to 400 °C. The maximum visible light transparency of the superhydrophobic glass was 92.4% compared to the uncoated glass (93.3%). Thus, making transparent superhydrophobic surfaces by a simple and straightforward process can be potentially used in self-cleaning glasses for various engineering applications.

An innovative strategy for improving the performance of forward osmosis membrane: stripe-like Turing structure constructed by introducing hydrophilic polyvinylpyrrolidone

Improving the performance of forward osmosis (FO) membranes has always been moving forward. Here we fabricate the novel Turing structures in the active layer (AL) of thin film composite (TFC) membrane through effectively introducing the polyvinylpyrrolidone (PVP) macromolecule with hydrophilicity both in the support layer (SL) and AL. The addition of PVP facilitates the formation of sponge-like pores in the SL and stripe-like Turing structures in the AL. The influence of PVP on the morphology and performance of the membranes was investigated by SEM, AFM, XPS, NMR, FTIR. Compared with the water flux (Jw) of the original composite membrane (approximately 25 L m−2 h−1), TFC-PVP (3:1) membrane with Turing structure achieved better performance (approximately 75 L m−2 h−1), and the reverse solute flux/water flux (Js/Jw) value was as low as 0.02 g/L. This study demonstrated that the Turing structures have a favorable effect on the performance of FO membrane and a promisingly practical application in water treatment.

The effect of different solvents on the morphology and performance of the ZIF-8 modified PVDF ultrafiltration membranes

In this research, the PVDF-based nanocomposite membranes modified with ZIF-8 nanocrystals were prepared with various casting solvents containing, DMSO, NMP, DMF and DMAc. The SEM, EDX and AFM analyses were applied to study morphology, distribution of the ZIF-8 in the matrix of the polymer, and surface roughness characteristic of the mixed matrix membranes, respectively. The impact of the solvent type on the structure and filtration efficiency of the resulting membranes was studied by considering the thermodynamic and kinetic factors of the membrane formation. A significant correlation was found between the diffusion rates of the solvent/non-solvent and the sub-layer structure of the membranes. Membranes cast with DMAc and DMF solvents (with relatively high diffusion rates) presented a bigger number of the finger-like cavities with a smaller size compared with membranes prepared by DMSO and NMP with lower diffusion rates. Blending of the ZIF-8 nanoparticles within the membrane matrix with a proper concentration (up to 0.2 wt%) resulted in an increase in the size of the finger-like cavities, lead to increase in the permeability of the resulting membranes. With increasing the ZIF-8 content to 0.5 and 1 wt%, the finger-like pores turned to sponge-like pores. The pure water permeation of the unmodified membranes cast with DMSO, NMP, DMAc and DMF was 258.64, 179.52 156.65 and 10.52 L/m2h, respectively, which was in good agreement with the observed trend for porosity and surface hydrophilicity of the membranes.

Lyotropic Liquid Crystal-Based Membranes for Water Remediation: Fabrication, Characterization and Performance Evaluation.

In water remediation, biomimetic membranes are gaining much attention due to their selectivity, dynamic stability, nontoxicity, and biocompatibility. Lyotropic liquid crystals (LLCs) are self-organizing networks that can conform to an array of geometries with high pore densities. As such, LLCs are excellent membrane materials for water applications because they are water insoluble and are manipulated to conform to an array of morphologies that provide natural water channels that are readily tunable in size. They have the ability to create uniform pores, between the range of 1 and 5 nm, with large surface areas. Thus, this work focuses on the design, fabrication, and characterization of LLC-modified Janus-type membranes for forward osmosis applications. Physical characterization of the membranes was performed using scanning electron microscopy (SEM), and the results show an open-pore radius and the presence of both finger- and sponge-like pores depending on membrane preparation. The contact angle assessment indicates that as the membranes are further modified with other polymers (e.g., PAN), higher hydrophilicity and surface energy are achieved. Moreover, the Brunauer–Emmett–Teller (BET) analysis showed a significant variation in the pore distribution between membranes. Functionalized membranes presented satisfactory water flux and superior salt rejection compared to nonfunctionalized membranes. SupPACMoDS membranes are 83% more efficient at preventing salt back flux than the nonmodified version. This is credited to the thickness and pore structure provided by the PAN support layer in the membrane.

Magnetic array-templated method for fabrication of polymer nanoporous films

This paper describes the development of a novel method of producing nanoporous polymeric membranes in a cost-effective and reproducible manner. The novelty of the technique hinges on the exploitation of a new type of sacrificial material & structures - self-assembled arrays of magnetic nanoparticles. The arrays are obtained through application of an external magnetic field to a thin layer of colloidal solution of superparamagnetic nanoparticles in a polymerizable monomer; this is followed by photopolymerisation. The resulting columnar structures form the pore templates which when selectively etched away leave an array of nanopores spanning across the polymeric film. The morphological characterisation of the nanopores by scanning electron microscopy and ionic conductivity revealed a very unusual sponge-like pore morphology. The applications which would benefit from the specific pore morphology and arrayed manufacturing are discussed.

Preparation of chitosan graft benzo-15-crown-5/non-woven fabric composite membrane for enhanced Pd2+ adsorptive separation

ABSTRACT Based on the selectively complexing properties of crown ethers for metal ions, a chitosan-graft-benzo-15-crown-5 ether (CTS-g-B15C5)/non-woven fabric (NWF) composite membrane with sponge-like pore structure was prepared. A flow-through dynamic adsorption method was used to investigate the adsorptive separation performance for Pd2+. The thermodynamic analysis revealed that Pd2+ adsorption on the composite membrane was a spontaneous procedure in which the high temperature would benefit the adsorption. Moreover, the composite membrane showed excellent reusability after regeneration, and there was no obvious loss of adsorption amount after five cycles. Finally, the CTS-g-B15C5/NWF composite membrane retained high selectivity for Pd2+ in simulated nuclear wastewater.

Development of high-permeable PSf/PANI-PAMPSA composite membranes with superior rejection performance

Polysulfone is the most popular polymeric matrix material for fabrication of ultrafiltration membrane but suffers from its hydrophobic nature that caused low flux and fouling problems that limits its development and industrial applications. The blending PSf with hydrophilic polymers is an attractive and effective technique to improve the hydrophilicity of membrane. Here poly(2-acrylamido-2-methyl-1-propane sulfonic acid doped polyaniline was synthesized and used as a hydrophilic additive in polysulfone to obtain ultrafiltration range membranes with higher flux. Infrared results supported the increased hydrophilicity of the membranes with PANI-PAMPSA additive which is confirmed by dynamic contact angle analysis results as well. The cross-sectional SEM images revealed that the pristine and blend membranes were asymmetric structured and had dense skin layer, finger-like pores on the top and sponge-like pores underneath the porous support layer. Also, the skin layer of the membrane became thinner and denser with the addition of 0.1 and 0.25 % and thicker with the addition of 0.5 additive ratio. The initial contact angles of P0, P1, P2 and P3 measured as 85, 81, 79 and 72°, respectively. Pure water permeability of the P0, P1, P2 and P3 membranes calculated as 14.0, 17.2, 23.4 and 21.3 L.m−2. h−1. bar−1, respectively. The rejection ratios of the prepared membranes increased from 90.1 (P0) to 95.8 and 98.4 % for P1 and P2 membranes then decreased to 95.2 % for P3 membrane. The rejection results indicated that the prepared membranes can be classified as ultrafiltration membranes with molecular weight cut-offs (MWCOs) lower than 66 kDa g mol−1.

Surface-concentrated chitosan-doped MIL-100(Fe) nanofiller-containing PVDF composites for enhanced antibacterial activity

Antibacterial properties are a major issue for the membrane-based wastewater treatment since the biofilm on membranes generated by bacterial growth can significantly reduce water flux. Here, the surface-concentrated MIL-100(Fe)/chitosan (MIL100-CS)-embedded polyvinylidene fluoride (PVDF) composite membranes (i.e., PVDF-S/MIL100-CS) were successfully fabricated by the newly developed fabrication method, so-called solvent-assisted nanoparticle embedding (SANE). The SANE method was modified from the conventional nonsolvent-induced phase separation method by the addition of an intermediate step for the selective arrangement of hydrophilic nanofillers on top of the nascent PVDF film. The additional step in the SANE method enabled the surface-selective filler distribution with the open surface of fillers, resulting in the hydrophilic surface. Also, it facilitated to form the sponge-like pore structures mostly due to the dilution effect of additional solvent. The PVDF/MIL100-CS microfiltration (MF) composite membranes acquired by SANE exhibited the higher antibacterial activity and the substantially enhanced biofouling resistance for E. coli cells than those of the pristine PVDF due to the surface-selective arrangement of MIL100-CS fillers which include both hydrophilic and biocidal properties. The live/dead test for antibacterial activities with E. coli cells further confirmed the enhanced suppression of the biofouling resistance in the asymmetric PVDF/MIL100-CS composite membranes relative to that of PVDF. Our current study offers a new platform for fabricating asymmetric MF composite membranes with enhanced antibacterial activity and biofouling resistance.

Dual-Resolution Microstructural Analysis of Anisotropic Pore Structure in SOFC Anode Fabricated by Phase-Inversion Tape Casting

The phase-inversion tape casting technique is used for fabrication of Ni-YSZ anode substrate for solid oxide fuel cells to form anisotropic pore structures and hence to improve its gas transport property. Microstructure of the fabricated anode substrates is analyzed using the scanning electron microscope with dual resolutions: one at 10 µm scale to analyze the sponge-like pores and the other at 500 µm scale to analyze the anisotropic finger-like pores. Depth profile of the microstructural parameters is also obtained. SOFC cells are prepared with the anode substrates and their electrochemical performance is evaluated by the electrochemical impedance spectroscopy and compared with that of the conventional cell. The anode fabricated using the phase-inversion tape casting is found to have excellent gas transport property even at high current and diluted hydrogen conditions.

Advanced Porous Membranes with Tunable Morphology Regulated by Ionic Strength of Nonsolvent for Flow Battery.

A simple salt-induced phase separation method is presented to prepare porous polybenzimidazole (PBI) membranes with tunable morphology for vanadium flow batteries (VFBs). This method is based on the traditional nonsolvent-induced phase separation (NIPS) method where salt is introduced into the coagulation bath to change the ionic strength of the nonsolvent. The change of ionic strength will affect the phase separation rate, and finally, the morphology of porous membranes is well tuned from finger-like voids to sponge-like pores in site. The membrane with sponge-like pores created multiple barriers to the transfer of vanadium ions, offering the membrane with superhigh selectivity; meanwhile, spongy cells filled with sulfuric acid could provide the membrane with high proton conductivity. As a result, the membrane with sponge-like pores demonstrated a much better performance than that with finger-like voids. The resultant sponge-like porous PBI membrane exhibited a very impressive VFB performance with an energy efficiency of 89.9% at a current density of 80 mA cm-2, which was close to the highest values ever reported. The battery kept very stable performance even after continuously running for more than 10000 cycles at 160 mA cm-2, showing excellent stability. This paper provides an easy to scale up and environment-friendly method to fabricate high-performance porous membranes with tunable morphology.

Electrochemical properties of micro-tubular intermediate temperature solid oxide fuel cell with novel asymmetric structure based on BaZr0.1Ce0.7Y0.1Yb0.1O3−δ proton conducting electrolyte

This study employed a simple phase-inversion method to achieve anode-supported micro-tubular solid oxide fuel cells on the basis of the BaZr0.1Ce0.7Y0.1Yb0.1O3−δ proton conducting electrolyte. The typical cell with configuration of Ni–BaZr0.1Ce0.7Y0.1Yb0.1O3−δ|BaZr0.1Ce0.7Y0.1Yb0.1O3−δ|La0.6Sr0.4Co0.2Fe0.8O3-δ-Sm0.2Ce0.8O2-δ. The novel “sponge-like micro-pores electrode | homogeneous porous functional layer” asymmetric pore structure is obtained. Achieved results include: i) the electrodes revealed the single phase collected by the powder X-Ray Diffractometer analysis; ii) observed by Scanning Electron Microscope, the single cell presenting uniform distribution of micro sponge-like pores electrode was well-adhered to the dense and crack-free 12 μm thick electrolyte layer; iii) the cells showed excellent electrochemical performance with the maximum power densities of 1.070, 0.976, 0.815, and 0.700 W cm−2 at 750, 700, 650 and 600 °C, respectively, characterized by Electrochemical Impedance Spectroscopy; iv) the designed cell clearly indicated a very low concentration polarization value (0.01 and 0.02 Ω cm2 at 750 and 700 °C). Our findings provide a promising approach to improve intermediate temperature solid oxide fuel cells performance by optimizing the electrode-electrolyte interface microstructure, based on proton and oxide ion mixed conductor electrolytes.

High performance of anode supported BaZr0.1Ce0.7Y0.1Yb0.1O3-δ proton-conducting electrolyte micro-tubular cells with asymmetric structure for IT-SOFCs

A simple phase-inversion method is employed to achieve anode-supported micro-tubular solid oxide fuel cells based on BaZr0.1Ce0.7Y0.1Yb0.1O3-δ proton conducting electrolyte. The whole-cell configuration is Ni-BaZr0.1Ce0.7Y0.1Yb0.1O3-δ|BaZr0.1Ce0.7Y0.1Yb0.1O3-δ | La0.75Sr0.25MnO3-δ-Sm0.2Ce0.8O2-δ. The novel asymmetric structure of “sponge-like micro-pores electrode | homogeneous porous functional layer” is obtained. The results achieved in the present work include: i) the electrodes reveal the single phase collected by the powder X-Ray Diffractometer analysis; ii) the single cell exhibits uniform distribution of micro sponge-like pores electrodes are well-adhered to the dense, crack-free 12μm thick electrolyte layer observed by Scanning Electron Microscope; iii) the cells show excellent electrochemical performance with the maximum power densities of 1.01, 0.89, 0.75 and 0.58W·cm−2 at 750, 700, 650 and 600°C, respectively, characterized by Electrochemical Impedance Spectroscopy; iv) the cell design especially reveal very low concentration polarization values (0.014–0.019Ω·cm2 at 750–600°C).

Triple-Layered Carbon-SiO2 Composite Membrane for High Energy Density and Long Cycling Li–S Batteries

Here we report a highly scalable yet flexible triple-layer structured porous C/SiO2 membrane via a facile phase inversion method for advancing Li-sulfur battery technology. As a multifunctional current-collector-free cathode, the conductive dense layer of the C/SiO2 membrane offers hierarchical macropores as an ideal sulfur host to alleviate the volume expansion of sulfur species and facilitate ion/electrolyte transport for fast kinetics, as well as spongelike pores to enable high sulfur loading. The triple-layer structured membrane cathode enables the filling of most sulfur species in the macropores and additional loading of a thin sulfur slurry on the membrane surface, which facilitates ion/electrolyte transport with faster kinetics than the conventional S/C slurry-based cathode. Furthermore, density functional theory simulations and visual adsorption measurements confirm the critical role of the doped SiO2 nanoparticles (∼10 nm) in the asymmetric C membrane in suppressing the shuttle effect of polysulfides via chemisorption and electrocatalysis. The rationally designed C/SiO2 membrane cathodes demonstrate long-term cycling stability of 300 cycles at a high sulfur loading of 2.8 mg cm-2 with a sulfur content of ∼75%. This scalable yet flexible self-supporting cathode design presents a useful strategy for realizing practical applications of high-performance Li-S batteries.

Ionic liquid grafted polyamide 6 as porous membrane materials: Enhanced water flux and heavy metal adsorption

The design and preparation of new membrane material are of great importance. In this work, a hydrophilic ionic liquid (IL) grafted polyamide 6 (PA6) (IL-g-PA6) porous membrane materials were designed and prepared via radiation induced grafting method. The improved hydrophilicity, solubility and the unique ion structure of IL-g-PA6 made it suitable to prepare porous membrane using simple immersion precipitation phase inversion method. SEM images showed opened sponge-like pores for both PA6 and IL-g-PA6 porous membranes, while the pore size decreased and porosity increased as ionic liquid was grafted on PA6. It is believed that the mass transfer process was slowed down by enhanced hydrophilicity and solubility of IL-g-PA6, which lead to a different porous structure from that of PA6. Besides, even though the pore size of 2%-50 K membrane was much smaller, the water flux of which was 2.6 times higher than that of PA6 membrane. Moreover, the chromate sorption on 8%-50 K membrane was 2.7 times higher than that of PA6 membrane, which implies that the IL-g-PA6 porous membranes are good sorbent for heavy metal ions. The special interaction between grafted ionic liquid and heavy metal ions would account for the excellent adsorption property.

Fabrication and characterization of cellulose triacetate porous membranes by combined nonsolvent-thermally induced phase separation

Cellulose triacetate (CTA) porous membranes were firstly prepared by the combined nonsolvent-thermally induced phase separation (N-TIPS) method. Dimethyl sulfone (DMSO2) and polyethylene glycol (PEG400) were respectively chosen as the TIPS solvent and additive of CTA, while water was used as the NIPS nonsolvent. Their Hansen solubility parameters were analyzed to understand the solution thermodynamics. Detailed investigation was applied on the effects of the polymer concentration, the coagulation bath temperature and the coagulation bath composition on the CTA porous membranes. It is found that both NIPS and TIPS effects simultaneously exist and compete with each other, and further affect the membrane morphology and performance. The NIPS effect can be promoted by lowering the CTA concentration or elevating the coagulation bath temperature, resulting in figure-like macropores and porous top surface. The obtained CTA porous membranes show a water flux as high as 2002.9 ± 55.2 L/m2h. On the contrary, the TIPS effect becomes the dominant factor, and leads to the symmetric sponge-like pores, which facilitate to enhance the mechanical properties. Besides, CTA porous membranes present large surface pore size as well as low fraction of figure-like macropores as increasing the DMSO2 content in the coagulation bath. These CTA porous membranes with excellent water permeability and mechanical strength are promising candidates for microfiltration or the porous substrates of thin film composite membranes.

Microfluidic continuous flow synthesis of functional hollow spherical silica with hierarchical sponge-like large porous shell

Microfluidics brings unique opportunities for engineering micro-/nanomaterials with well-controlled physicochemical properties. Herein, using a miniaturized multi-run spiral-shaped microreactor, we develop a flow synthesis strategy to continuously produce hollow spherical silica (HSS) with hierarchical sponge-like pore sizes ranging from several nanometers to over one hundred nanometers. The formation of HSS is realized by mixing two reactant flows, one containing cetyltrimethylammonium bromide (CTAB) and diluted ammonia and the other 1,3,5-trimethylbenzene (TMB) and diluted tetraethyl orthosilicate (TEOS), at a flow rate as high as 5 mL/min. The effect of the reactant concentration and the flow rate on the structural change of the resultant materials is examined. Functional small-sized nanoparticles (magnetic nanoparticle, quantum dot, and silver nanoparticle) can be separately assembled into HSS and high molecular weight protein (bovine serum albumin) can be successfully loaded into HSS and delivered into cancer cells afterward, making them promising in the fields of separation and purification, bioimaging, catalysis, and theranostics.

The Anti-compaction Behavior of Aramid Fiber Based Polyvinylidene Fluoride Composite Separation Membranes

Poly(p-phenylene terephthalamide) (PPTA), as the raw polymer material of Aramid fiber-1414, has high modulus and high strength which is commonly used in the reinforced composites. However, the general blending often accompany the microphase incompatibility in polymer matrix. In this study, PPTA molecules were incorporated into poly(vinylidene fluoride) (PVDF) membrane matrix through in situ polycondensation of p-phenylene diamine (PPD) and terephthaloyl chloride (TPC) in PVDF solution and PPTA/PVDF molecular composite membranes were prepared via the subsequent nonsolvent induced phase separation (NIPS) process. The anti-compaction properties of resulted PPTA/PVDF molecular composite membranes were systematically investigated including the variations of bursting pressure and membrane thickness, porosity, pure water flux under different pressures. The results suggested that membrane comprehensive anticompaction properties were improved with the increasing of PPTA content in PVDF membrane matrix. Combining the variation trends of membrane anti-compaction properties with morphologies, the compaction-deformation evolution processes of two membrane pore types (sponge-like and finger-like pores) were proposed at the end.