Honeycomb-like Porous Structure Research Articles

From biological waste to honeycomb-like porous carbon for high energy density supercapacitor

We develop a facile and sustainable method for the synthesis of three-dimensional (3D) interconnected honeycomb-like porous carbon (HPC) derived from sunflowers stem. The optimized sample has large specific surface area with 3D interconnected honeycomb-like porous structure and high oxygen content. Due to their synergistic effect, the HPC-2 material shows a high specific capacitance of 349 F g−1 at 1 A g−1, good rate capability (247 F g−1 at 50 A g−1) and excellent cycling stability (retaining 98.6% after 10000 cycles) in 6 M KOH aqueous electrolyte. Moreover, the HPC-2//HPC-2/MnO2 asymmetric supercapacitor shows a high energy density of 58.8 W h kg−1 and good electrochemical stability (83.1% of initial capacitance retention after 10000 cycles). Therefore, these unique properties enable the material to become a promising high-performance electrode material for supercapacitors.

Construction of atomically ultrathin 3D flower-like α-Co(OH)2 hierarchical microspheres with gradually “OH−-incursion” outside-inside strategy

A new 3D flower-like α-Co(OH)2 hierarchical microspheres with dodecyl benzene sulfate (DBS)-intercalated structure has been fabricated by employing a solvothermal method. The DBS-α-Co(OH)2 structure can be synergistically determined by various characterization methods (EDS, TGA, FTIR and XPS). Moreover, the DBS-α-Co(OH)2 microspheres exhibit a novel morphology with a range of hierarchically honeycomb-like porous structures formed between the neighboring Co(OH)2 nanosheets. And the thickness of the ultrathin Co(OH)2 nanosheet has been determined to be only 2.4–4.0 nm (4–6 single atomically thick layers) to gain a specific surface of Co(OH)2 microspheres as 210.54 m2 g−1. Due to the morphological evolution of the precursor, an innovative growth mechanism has been proposed and the formation of 3D flower-like Co(OH)2 hierarchical microspheres can be induced by a gradual “OH−-incursion” with an outside-inside strategy on basis of the transition state.

Decreased <em>Porphyromonas gingivalis</em> adhesion and improved biocompatibility on tetracycline-loaded TiO<sub>2</sub> nanotubes: an in vitro study

BackgroundTitanium dioxide (TiO2) nanotubes are often used as carriers for loading materials such as drugs, proteins, and growth factors.Materials and methodsIn this study, we loaded tetracycline onto TiO2 nanotubes to demonstrate its antibacterial properties and biocompatibility. The two-layered anodic TiO2 nanotubes with a honeycomb-like porous structure were fabricated by using a two-step anodization, and they were loaded with tetracycline by using a simplified lyophilization method and vacuum drying. Their physical properties, such as chemical compositions, wettability, and surface morphologies of the different samples, were observed and measured by X-ray photoelectron spectroscopy (XPS), contact angle measurement, and scanning electron microscopy (SEM). The in vitro growth behaviors of mouse bone marrow stromal cells (BMSCs) on these substrates were investigated.ResultsThe TiO2 nanotube (NT) substrates and the tetracycline-loaded TiO2 nanotube (NT-T) substrates revealed a crucial potential for promoting the adhesion, proliferation, and differentiation of BMSCs. Similarly, the NT-T substrates displayed a sudden release of tetracycline in the first 15 minutes of their administration, and the release tended to be stable 90 minutes later. The antibacterial performances of the prepared substrates were assessed with Porphyromonas gingivalis. The result showed that NT and NT-T substrates had antibacterial capacities.ConclusionOverall, this research provides a promising method with potential for clinical translation by allowing local slow release of antimicrobial compounds by loading them onto constructed nanotubes.

Honeycomb-like nitrogen and sulfur dual-doped hierarchical porous biomass carbon bifunctional interlayer for advanced lithium-sulfur batteries

The nitrogen and sulfur dual-doped hierarchical porous biomass carbon (NSHPC) is prepared by a simple and environment-friendly one-step method and employed as flexible interlayer for lithium-sulfur batteries (LSBs). The composition analysis and structure characteristic of NSHPC sample are measured by X-ray powder diffraction, scanning electron microscopy and Raman spectra. The electrochemical performances are measured by galvanotactic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurement. The results show that the NSHPC sample with unique honeycomb-like micro/mesoporous structure possesses high specific surface area of 2543.8 m2 g−1 and large pore volume of 2.14 cm3 g−1. The charge transfer resistance (Rct) of the LSBs with the NSHPC flexible interlayer is much smaller than that of the LSBs with only Celgard separator. The pure sulfur cathode using NSHPC flexible interlayer can exhibit a high initial discharge capacity of 1549 mAh g−1 at 0.1 C. The good cycle performance and high discharge capacity are mainly owing to the honeycomb-like porous structure and the electrostatic repulsion between lithium polysulfides (LiPSs) and nitrogen and sulfur dual-doping of NSHPC flexible interlayers. The using of NSHPC flexible interlayer to modify the Celgard separator can availably reduce the charge transfer resistance and increase electrostatic repulsion to LiPSs, and further enhancing the performance of LSBs.

Facilitation of lithium polysulfides adsorption by nitrogen doped carbon nanofibers with 3D interconnected pore structures for high-stable lithium-sulfur batteries

Lithium-sulfur battery is one of the most prospective chemistries in secondary energy storage field due to its high energy density and theoretical capacity, but the rapid decay of capacity is still a huge challenge. Herein, we reported an ingenious design of nitrogen doped carbon nanofibers with honeycomb-like porous structure for the cathode of lithium-sulfur battery which can effectively suppress the “shuttle effect”. The special porous material with three dimensional (3D) interconnected pore structure is beneficial to enhance the adsorption of lithium polysulfides and accommodate the volume expansion of active materials. In addition, the doped nitrogen can not only improve the conductivity of cathode, but also form a strong interfacial interaction to trap lithium polysulfides. Therefore, the battery with the cathode exhibited a high reversible discharge capacity of 1093.9 mAh g−1 and good capacity retention of 76.0% after 300 cycles at 0.5C rate. After acidification, the cycling performance of the cathode could achieve upon 300 cycles with a very low decay rate of 0.027% at 0.5C.

Facile synthesis of microporous carbons with three-dimensional honeycomb-like porous structure for high performance supercapacitors

Microporous carbons (MPC) with three-dimensional (3D) honeycomb-like porous structure is synthesized by a simple and convenient carbonization method using polyvinyl alcohol (PVA) as carbon source and KOH as both activating agent and template. Benefiting from its large surface area, 3D interconnected honeycomb-like porous structure and high oxygen doping, the MPC-2 electrode exhibits a high specific capacitance of 367 F g−1 at 0.5 A g−1 and excellent electrochemical stability (99.7% of its initial capacitance after 10,000 cycles) in 6.0 M KOH aqueous electrolyte. More importantly, the assembled MPC-2 symmetric supercapacitor shows an energy density of 22.4 Wh kg−1 based on the total mass of active materials of the two electrodes in 1.0 M Na2SO4 aqueous electrolyte, as well as excellent electrochemical stability. Therefore, this work provides an easy, convenient way to design and large-scale produce 3D honeycomb-like porous carbon for high performance supercapacitors.

Promising biomass-derived nitrogen-doped porous carbon for high performance supercapacitor

We proposed a simple strategy of one-pot carbonization, activation and nitrogen-doped processes to prepare biomass-derived nitrogen-doped porous carbon (NPC-K) by using well-sourced dumpling flour as carbon precursor, urea as nitrogen precursor and KOH as activation agent. In this process, the combination of KOH and urea was used to construct a highly porous structure because of their synergistic effect. The as-prepared NPC-K exhibited honeycomb-like porous structure, large specific surface area (2853.6 m2 g−1) and moderate nitrogen content. Therefore, the NPC-K displayed maximum specific capacitance of 311 F g−1 at 1 A g−1, outstanding rate capability and long lifetime of 10000 cycles in 6M KOH. Furthermore, NPC-K based symmetrical supercapacitor presented a high energy density of 15.92 Wh kg−1. These results are superior to many previously reported carbon materials.

Effect of Thermostable α-Amylase Addition on Producing the Porous-Structured Noodles Using Extrusion Treatment.

The rehydration and palatability properties of HENs were greatly improved by creating a well-developed or honeycomb-like porous structure using TαA at low concentration. The findings of this study could be applied to enhance the quality characteristics of HENs and to encourage the research and development in the noodle industry.

Popcorn-Derived Porous Carbon Flakes with an Ultrahigh Specific Surface Area for Superior Performance Supercapacitors.

Popcorn-derived porous carbon flakes have been successfully fabricated from the biomass of maize. Utilizing the "puffing effect", the nubby maize grain turned into materials with an interconnected honeycomb-like porous structure composed of carbon flakes. The following chemical activation method enabled the as-prepared products to possess optimized porous structures for electrochemical energy-storage devices, such as multilayer flake-like structures, ultrahigh specific surface area (SBET: 3301 m2 g-1), and a high content of micropores (microporous surface area of 95%, especially the optimized sub-nanopores with the size of 0.69 nm) that can increase the specific capacitance. The as-obtained sample displayed excellent specific capacitance of 286 F g-1 at 90 A g-1 for supercapacitors. Moreover, the unique porous structure demonstrated an ideal way to improve the volumetric energy density performance. A high energy density of 103 Wh kg-1 or 53 Wh L-1 has been obtained in the case of ionic liquid electrolyte, which is the highest among reported biomass-derived carbon materials and will satisfy the urgent requirements of a primary power source for electric vehicles. This work may prove to be a fast, green, and large-scale synthesis route by using the large nubby granular materials to synthesize applicable porous carbons in energy-storage devices.

New insights for phase-change immersion cooling enhancement of solar cells under high concentration ratios

To answer how surface corrosion affects the heat transfer performance of phase-change immersion cooling solar cells, electrochemical etching was used for substrate surface treatment of simulated dense-array solar cells in this paper. Morphology, roughness, and wettability of treated surfaces were characterized by scanning electron microscope, atomic force microscope, and spreading area, respectively. A self-running cooling system was developed to investigate the effect of surface treatment on self-running characteristics and heat transfer performance under different ethanol inlet temperatures and concentration ratios. The results show that the surface treated for 2 hours owns higher wettability because of the honeycomb-like porous structure. Lower ethanol flowing velocity obtained under lower ethanol inlet temperature with treated samples. The maximum declined degree in the wall superheating of 21.1% and the maximum enhancement in the heat transfer coefficient of 33.3% are obtained for sample treated for 2 hours because of its higher wettability and porosity structure. The results show that electrochemical etching on substrate surface can improve the phase-change immersion cooling performance of solar cells.

Layer-by-layer assembled polyelectrolytes on honeycomb-like porous poly(ε-caprolactone) films modulate the spatial distribution of mesenchymal stem cells

Cellular behaviors can be affected by both surface chemistry and topography of biomaterials substrates. The object of the present study was to investigate how pore structure and bioactive molecules regulate the adhesion and proliferation of rabbit bone marrow-derived mesenchymal stem cells (rMSCs) in synergy. Poly(ε-caprolactone) (PCL) films with a honeycomb-like porous structure were fabricated via a breath-figure method, and then further coated with bioactive molecules including four combinations of polyelectrolytes (GEL/CS, GEL/HA, CHI/CS and CHI/HA) via a layer-by-layer self-assembly (LBL) process. rMSCs were seeded on these films to evaluate both adhesion and proliferation. It was shown that a uniform honeycomb-like porous structure with a pore size of 18.87±3.25μm was obtained in the films. Bioactive molecules were proven to be successfully deposited on the films, the amount of which increased with the number of assembled layer. Both surface pore structure and assembled molecules play significant roles on the adhesion and proliferation of rMSCs. Notably, the spatial distribution of cells (either entrapped in pores or spreading over pores) on porous films was also dictated by the identity of the assembled molecules. These findings might be fundamental to design bioactive scaffolds for tissue engineering.

Self-Organized TiO2 Nanotubes: Influence of the Ti Microstructure on the Nanotube Growth

The synthesis of highly-ordered nanostructures of valve metal oxides has recently attracted huge scientific and technological interest motivated by their possible use in many applications. The most established member of this group of materials is nanoporous Al2O3, which has been prepared two decades ago by anodic oxidation of Al into perfectly ordered, honeycomb-like porous structures employing suitable electrochemical conditions [1]. Owing to the flexibility of the pore diameter/length and the relative ease of the Al2O3 dissolution, its porous membranes have been since than widely used as template material of choice for a range of materials [2-4]. Recently, TiO2 has received the highest attention after Al2O3 motivated by its range of applications, including photocatalysis, water splitting, solar cells and biomedical uses. Very significant research efforts have led to reproducible synthesis of self-organized TiO2 nanotube layers by means of anodic oxidation, during which the starting Ti substrate is converted into a highly-ordered nanotubular layer by anodization in suitable electrolytes [5-7]. Although advancements in the anodic synthesis of self-organized TiO2 nanotube layers have been presented over the past years [8], the degree of ordering has not reached so far the level known from porous alumina [1]. Numerous factors influence the ordering and the homogeneity of the TiO2 nanotube layers. In the presentation, we demonstrate significant advancements in the understanding of the influence of Ti substrates on the TiO2 nanotube growth compared to the recent state-of-art. Using SEM, AFM, GDOES and optical measurements we will show how to obtain a high degree of ordering, uniformity and homogeneity in the nanotube structure of TiO2 by tailoring the anodization protocol [9, 10]. Furthermore, based on SEM, EBSD and TEM measurements, we will demonstrate how the Ti grain structure influences the lateral uniformity of the nanotube layers [11].

Synthesis of honeycomb-like mesoporous nitrogen-doped carbon nanospheres as Pt catalyst supports for methanol oxidation in alkaline media

This paper reports the convenient synthesis of honeycomb-like mesoporous nitrogen-doped carbon spheres (MNCS) using a self-assembly strategy that employs dopamine (DA) as a carbon and nitrogen precursor and a polystyrene-b-poly(ethylene oxide) (PS173-b-PEO170) diblock copolymer as a soft template. The MNCS have large BET surface areas of up to 554m2g−1 and high nitrogen contents of up to 6.9wt%. The obtained MNCS are used as a support for Pt catalysts, which promote methanol oxidation in alkaline media. The MNCS-supported Pt (Pt/MNCS) catalyst has a larger electrochemically active surface area (ESA) (89.2m2g−1) than does a commercially available Vulcan XC-72R supported Pt/C catalyst. Compared to the Pt/C catalyst, Pt/MNCS displays a higher peak current density (1007mAmg−1) and is more stable during methanol oxidation. These improvements are attributed to the honeycomb-like porous structure of the MNCS and the introduction of nitrogen to the carbon support. The MNCS effectively stabilize Pt nanoparticles and assuage the agglomeration of the nanoparticles, suggesting that MNCS are potential and promising application as electrocatalyst supports in alkaline direct methanol fuel cells.

Preparation and characterization of PVA-based carbon nanofibers with honeycomb-like porous structure via electro-blown spinning method

The PVA-based carbon nanofibers with honeycomb-like carbon porous structure were successfully prepared by electro-blown spinning (EBS), pretreatment and carbonation processes. PVA was used as the carbonized polymer while PTFE was used as the sacrificial polymer. The carbon nanofibers with various pore sizes and distribution were prepared by varying the amount of PTFE loading in the spinning solution and optimizing carbonized parameters. The honeycomb-like carbon nanofibers were investigated by scanning electron microscopy (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectrum and low temperature nitrogen adsorption. It was found that specific surface area and pore volume could reach 591.33 m2 g−1 and 0.58 cm3/g, respectively, and large amount of micro-, meso- and macro-pores existed in this kind of porous carbon fiber when the PVA/PTFE was 1:15. This porous carbon nanofiber with special structure and high yield may realize the applications in the fields of adsorption, ion exchange, catalyst supports, etc., and the prepared method has a great industrialization potentiality.

A facile method for preparing 3D graphene/Ag aerogel via gamma-ray irradiation

ABSTRACTIn this article, we report a simple method to fabricate graphene and Ag nanoparticles (NPs) composite aerogel (GA/Ag). The GO and Ag ions were in situ reduced by gamma-ray irradiation and went through self-assembly three-dimensional (3D) honeycomb-like porous composite aerogel in the presence of isopropanol. Measurements using XRD, XPS, SEM, TEM revealed that the GO and Ag ions can efficiently reduction into rGO and Ag NPs. In addition, Ag NPs were homogeneously attached to the graphene nanosheets of the honeycomb-like porous structure and had a typical diameter of 30–70 nm. Thus the gamma-ray irradiation-induced synthesis is an efficient method for preparing 3D GA/Ag composite.

Super-Anticoagulant Heparin-Mimicking Hydrogel Thin Film Attached Substrate Surfaces to Improve Hemocompatibility.

In this study, heparin-mimicking hydrogel thin films are covalently attached onto poly(ether sulfone) membrane surfaces to improve anticoagulant property. The hydrogel films display honeycomb-like porous structure with well controlled thickness and show long-term stability. After immobilizing the hydrogel films, the membranes show excellent anticoagulant property confirmed by the activated partial thromboplastin time values exceeding 600 s. Meanwhile, the thrombin time values increase from 20 to 61 s as the sodium allysulfonate proportions increase from 0 to 80 mol%. In vitro investigations of protein adsorption and blood-related complement activation also confirm that the membranes exhibit super-anticoagulant property. Furthermore, gentamycin sulfate is loaded into the hydrogel films, and the released drug shows significant inhibition toward E. coli bacteria. It is believed that the surface attached heparin-mimicking hydrogel thin films may show high potential for the applications in various biological fields, such as blood contacting materials and drug loading materials.

Self-Organized TiO2 Nanotube Arrays: Towards Improved Ordering

Synthesis of highly-ordered nanostructures of valve metal oxides has recently attracted huge scientific and technological interest motivated by their possible use in many applications. The nanoporous Al2O3 – most established member of this group of materials – has been prepared by anodic oxidation of Al under suitable electrochemical conditions two decades ago into perfectly ordered, honeycomb-like porous structures (1). Owing to the flexibility of the pore diameter/length and the relative ease of the Al2O3 dissolution, its porous membranes have been since than widely used as template material of the choice for a range of materials (2-4). It is the TiO2 that has received the highest attention after Al2O3 motivated by its range of applications, including photocatalysis, water splitting, solar cells and biomedical uses. Very significant research efforts have led to reproducible synthesis of self-organized TiO2 nanotube layers by means of anodic oxidation, during which the starting Ti substrate is converted into highly-ordered nanotubular layer by anodization in suitable electrolytes (5-7). Although advancements in the anodic synthesis of self-organized TiO2 nanotube layers have been presented over past years (8), the degree of ordering has not reached so far the level known from porous alumina (1). Numerous factors influence the ordering and the homogeneity of the TiO2nanotube layers. In the presentation, we aim to demonstrate significant advancements in the ordering of anodic TiO2nanotubes compared to known state-of-art. In particular, we will show recent results on the extremely ordered nanotube arrays. In addition, utilizing AFM, SEM and optical measurements, we will show how to obtain via tailored anodization protocols a very decent degree of uniformity and homogeneity of the nanotube layers. Moreover, based on SEM, EBSD and TEM measurements, we will demonstrate how the Ti grain structure influences the lateral uniformity of the nanotube layers (9-11).

Gamma-ray irradiation-induced reduction and self-assembly of graphene oxide into three-dimensional graphene aerogel

Three-dimensional (3D) graphene aerogel (GA) with honeycomb-like porous structure and high C/O ratio was successfully prepared from graphene oxide (GO) dispersions in isopropanol/water solution by simple γ-ray irradiation and freeze-drying processes. Under irradiation, GO sheets suspending in the mixture were reduced and self-assembled mainly due to the restoration of π-π conjugated structure. The microstructure of GA was observed under different magnifications and the pores are quite uniform with pore size around 10µm. The reduction effect of GO was confirmed comprehensively by different characterizations. Briefly, γ-ray irradiation is an effective and green method for the reduction and self-assembly of GO sheets.

Tailored honeycomb-like polymeric films based on amphiphilic poly(urea/malonamide) dendrons

A series of hydrogen bond-rich poly(urea/malonamide) dendrons were utilized as surfactants to facilitate the formation of honeycomb-like porous structures from the breath figure (BF) process.

Electrodeposited porous Pb electrode with improved electrocatalytic performance for the electroreduction of CO2 to formic acid

A porous Pb foam was fabricated electrochemically at a copper substrate and then used as the cathode for the electroreduction of CO2. The surface morphology and composition of the porous Pb electrode was characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and selected area electron diffraction. The honeycomb-like porous structure was composed of needle-like Pb deposits. Cyclic voltammetry studies demonstrated that the porous Pb electrode had better electrocatalytic performance for the formation of formic acid from CO2 compared with a Pb plate electrode. The increase in current density was due to the large surface area of the porous Pb electrode, which provides more active sites on the electrode surface. The improved formic acid selectivity was due to the morphology of the roughened surface, which contains significantly more low-coordination sites which are more active for CO2 reduction. The highest current efficiency for formic acid was 96.8% at −1.7 V versus saturated calomel electrode at 5 °C. This porous Pb electrode with good catalytic abilities represents a new 3D porous material with applications for the electroreduction of CO2. Open image in new window