Open Pore Structure Research Articles

Facile synthesis of PtCo nanoparticles/three-dimensional graphene hybrid material as a highly active and stable electrocatalyst for oxygen reduction reaction

To further promote the widespread commercialization of proton exchange membrane fuel cells (PEMFCs), high performance oxygen reduction reaction (ORR) catalysts with high activity and stability must be developed to accelerate its sluggish kinetic process. Here, we report a successful synthesis of a novel hybrid material - highly synergistic PtCo nanoparticles (NPs) attached to three-dimensional graphene (PtCo @3DG). The PtCo @3DG exhibits excellent ORR performance, and the mass activity and specific activity measured at 0.9 V vs. RHE were 0.801 A/mgPt and 1.250 mA/cm2 respectively, which are 6.8 and 6.2 times higher than commercial Pt/C. High stability of this new material is achieved, which has demonstrated a loss of only 1.87% after an extensive 10,000 cycles test. The superior performance of PtCo @3DG can be primarily attributed to several key features, including its ultrathin size, a high Pt utilization, and a beneficial alloy effect. Additionally, the 3D graphene possesses an open and interconnected porous structure that facilitates efficient charge and mass transfer, which accelerates the desorption process of intermediates and exposes more active sites.

Processing and surface modification of titanium open cell porous structures for PEM fuel cell bipolar plates

Bipolar plate (BP) and porous transport layer (PTL) materials and designs are critical for the performance of a proton exchange membrane fuel cell (PEMFC) and electrolyser (PEMEC) due to their role as fluid distributor and electron transporter between cells. Designs based on open cell porous structures require a good control on the porosity features. The aim of this work is to use powder metallurgy to manufacture titanium porous structures and the use of suitable surface modification techniques that can improve the performance of the PEM systems, focusing on fuel cells. Using the space holder method, porous structures of up to 63% porosity and controlled pore size can be processed to tailor the characteristics for an optimal design and, through a simple gas nitriding treatment, the performance of the material in terms of interfacial contact resistance (below 10 mΩcm2 after corrosion) and corrosion resistance (below 1 μAcm−2) are improved for both dense and porous structures.

Optimization of dendritic TS-1/Silica micro–mesoporous composites for efficient hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene

A novel composite material (TD) composed of TS-1 microcrystalline and dendritic mesoporous silica nanospheres (DMSNs) was successfully prepared. The TD composite material had open pore structure and large specific surface area, which was conducive to the mass transfer of reactants and products. The Ti element in TS-1 could be used as an electron assistant, and the spillover d-electrons were conducive to the improvement of the sulfidation and dispersion of MoS2, thereby forming more type II MoS2 active phases. The incorporation of Ti could bring more Brønsted (B) and Lewis (L) acid, which was conducive to the hydrogenation pathway (HYD) selectivity (41.2%) of dibenzothiophene (DBT) hydrodesulfurization (HDS) and isomerization (ISO) route selectivity (21.9%) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS, thus improve the HDS activity of DBT and 4,6-DMDBT. NiMo/TD-70 (Aging temperature = 70 °C) had the best HDS activities of DBT (99.0%) and 4,6-DMDBT (93.7%) due to its large open pore structure, good acidity, suitable metal-support interaction (MSI) and perfect dispersion of the metallic active sites.

Biochar‐based interfacial evaporation materials derived from lignosulfonate for efficient desalination

AbstractThe solar‐driven interfacial evaporation has attracted great attention for the purpose of alleviating freshwater shortage. Lignosulfonate (LS), a main byproduct of sulfite pulping processes, is an abundant natural resource but has not been reasonably utilized. To mitigate the above problems, biochar‐based interfacial evaporators derived from LS for solar steam generation were studied in this paper. First, LS was used as a raw material for fabricating carbon materials by carbonization to construct LS‐derived carbon (CLS). Meanwhile, LS‐derived porous carbon (PCLS) in the presence of CaCO3 as the activator was also prepared. Next, the two biochar powders, as solar absorbers, were crosslinked with polyvinyl alcohol to prepare the interfacial evaporation materials (PVA@PCLS and PVA@CLS). The open porous structure facilitated the capillary effect and water transport to the evaporator surface. It was also found that the light absorption of the materials could reach more than 97% in the 250–2500 nm range. Moreover, the water evaporation rate and the solar‐to‐vapor conversion efficiency of PVA@PCLS and PVA@CLS were 2.33, 1.82 kg m−2 h−1, and 83.7%, 69.3% respectively under 1 sun (1 kW m−2) irradiation. The solar‐to‐vapor conversion efficiency of PVA@PCLS was much increased after the carbonization of LS. In addition, the material cost of PVA@PCLS is only $38.3/kg due to the low price of LS. Therefore, this work provides an economic and efficient strategy for solar‐driven desalination and a possible way for the high‐value utilization of lignin.

A 3D COF constructed by interlayer crosslinking of 2D COF as cathode material for lithium–sulfur batteries

The design and construction of three-dimensional covalent organic frameworks (3D COF) remains a major challenge, and it is necessary to explore new strategies to synthesize 3D COF with ideal structure. Here, we utilize two-dimensional covalent organic framework (2D COF) with allyl side chain to achieve interlayer crosslinking through olefin metathesis reaction, thereby constructing a 3D COF with cage-like structures. This new material named CAGE-COF has larger specific surface area and more open pore structure than the original 2D COF. The cathode material with CAGE-COF retained 78.7% of its initial capacity after 500 cycles, and the fading rate is 0.04% each cycle.

Preparation of porous TiNi intermetallic compound and the corrosion behavior in NaCl solution

Porous TiNi intermetallic compounds have a promising future as biomaterials, with some challenges for their corrosion resistance. In this work, TiNi intermetallic compound was prepared by reactive synthesis of elemental powders. The evolution of the microstructure and phase composition of TiNi at different temperatures was studied. And the electrochemical corrosion behavior of TiNi intermetallic compound in NaCl solution was investigated by electrochemical tests. The results show the formation of a core-shell structure during the sintering process, where Ni is the core and Ti2Ni, TiNi and TiNi3 are the shells. With uniform diffusion, a large pore replaces the Ni core due to the Kirkendall effect. TiNi intermetallic compound has a well-developed open pore structure with an open pore ratio of 50.98%. TiNi intermetallic compound exhibits better corrosion resistance compared to Ni and Ti, which can be attributed to the generation of passivation film on the surface.

A novel organic solvent-free method for manufacturing polyethersulfone hollow fiber membranes using melt extrusion

Hollow fiber membranes are traditionally manufactured using the spinning process, which takes advantage of the phase separation/inversion for the creation of a porous structure. In this work, the use of melt extrusion led to the fabrication of hollow fiber membranes without the use of organic solvents. Following post-treatment, the fabricated partially dense fibers are transformed into porous fibers. In detail, ternary blends of polyethersulfone/poly(ethylene glycol)/poly(N-vinyl pyrrolidone) (PESU/PEG/PVP) were developed by combining a solvent-free liquid mixture of PEG/PVP into PESU. Using a single screw extruder, this blend was melted and extruded using an annular slit nozzle where PEG functioned as a plasticizer, i.e., decreased processing temperatures, while PVP aided in retaining the hollow fiber geometry. These hollow fibers were comprised of uniformly closed pores, occurring due to the expansion and formation of bubbles of evaporating PEG nucleated by PVP during extrusion. By immersing these fibers into an aqueous solution of sodium hypochlorite (NaOCl), PEG and PVP were removed, which led to an open porous structure with pore sizes between 100 nm and 1 μm throughout the membrane. The outer surfaces of the hollow fibers were found to contain a higher PVP content than the inner surface. As PVP and PESU are miscible, i.e., blended in a single phase, treatment with NaOCl led to the creation of open pores on the outer surface with pore sizes between 10 and 150 nm, thus deeming the outer surface functional as a separation layer. The effect of blend composition, extrusion settings, and post-treatment parameters on membrane morphology, water flux, thermal characteristics, and tensile strength was studied, while after the modification, near-pristine PESU membranes were pursued. A water-flux of 28 L/h m2 bar and a molecular weight cut-off (MWCO) of 90%, 75%, and 40% for poly(ethylene oxide) of an average of 1000 kDa, 400 kDa, and 100 kDa molecular weight, respectively, proved that via extrusion it is possible to produce hollow fiber membranes for ultrafiltration without the use of organic solvents.

Sustainable and low-cost cellulose aerogel-based absorber for solar steam generation

Solar steam generation is a promising technology for sustainable seawater desalination. However, its practical application is hindered by the low water evaporation rate and the high cost of materials. Carbon aerogels have demonstrated superior properties for clean water production through solar steam generation, but the complex and time-consuming preparation process inhibits their development and applications. In this study, high-performance solar steam absorbers based on cellulose-derived carbon aerogels were prepared from paper and waste paper using a simple green method. The fabricated carbon aerogels have a typical microporous structure (pore diameter: 20–250 µm), super-hydrophilic properties, good mechanical properties and efficient solar light absorption (∼96 %), which make them ideal for application in solar steam generation. Three different configurations based on cellulose and carbon aerogels were fabricated (bulk absorber, double-layer absorbers and ink-based absorber) to achieve the best design with high efficiency for steam generation. The surface temperature of the bulk absorber and dry double-layer absorbercan achieve 100 °C under 1 kWm−2irradiation. Among all configurations, the double-layer absorbers represented the highest efficiencies, 90.4 % for paper and 84.3 % for waste paper, under 1 kWm−2 irradiation, which are higher than most reported results. According to the results, the sustainable cellulose-based double-layer absorbers were promising materials for efficient solar steam generation due to their high hydrophilicity, high sunlight absorption, open porous structure, non-toxicity, biodegradability, availability and low cost.

In-situ immobilization of MIL-100(Fe) on the microchannels in wood aerogel: Efficient persulfate activation toward antibiotic removal

Metal-organic frameworks (MOFs) are potential catalysts for persulfate exciting in antibiotic wastewater treatment while are limited in large-scale application given their powder state. Herein, benefiting from the compatibility and functionalization of natural wood supports, MIL-100(Fe) decorated wood aerogel composites (MIL-100(Fe)/WA) were constructed by chemical treatment and in-situ solvothermal synthesis. Na2SO3/NaOH-H2O2 chemical treatment could effectively achieve the partial removal of lignification and hemicellulose in wood, resulting in improved porous characteristics. The corresponding porosity and surface area of WA increased by more than 40% compared with the original wood. Accordingly, after immobilizing MIL-100(Fe) on the microchannels in WA, MIL-100(Fe)/WA-PDS system could efficiently degrade tetracycline (TC), with a satisfied mineralization rate of 64.01% owing to the open porous structure of WA with high accessibility, and its kinetic constant (0.0520 L⋅mg−1⋅min−1) was 6.19 times that of MIL-100(Fe)/wood (0.0084). Quenching results and EPR analysis made clear that TC degradation mainly contributed to the produced O2−, 1O2 and surface-bound radicals (SO4−, OH). LC-MS further uncovered the possible degradative pathways for TC. Moreover, it was found that MIL-100(Fe)/WA could behave well at pH of 2–10 and towards multiple antibiotics. This work may provide a facial way to apply MOFs-based/wood composites in water treatment.

Effects of cell morphology on the textural attributes of fruit cubes in freeze-drying: Apples, strawberries, and mangoes as examples.

The influence of cell morphology on the textural characteristic of freeze-dried apple, strawberry, and mango cubes was evaluated. Corresponding restructured cube samples without intact cell morphology were prepared as controls. Results indicated that the presence of cell morphology strengthened the shrinkage and collapse of samples during freeze-drying, especially in mangoes due to the high content of sugar. Intact cell morphology was found in natural fruit cubes after freeze-drying by scanning electron microscopy (SEM) observation, making them exhibit a more regular microporous structure, further resulting in higher hardness than the restructured cubes. However, the intact cell morphology negatively affected the crispness of freeze-dried cubes since it enhanced structural collapse. The freeze-dried samples without cell morphology would destroy the cellulose structure and form a continuous open-pore structure under the concentration effect of ice crystals during freezing, which accelerates the escape of water molecules, increases the drying rate, and avoid collapse. Sensory experiments found that restructured cubes without intact cell morphology exhibited greater comprehensive acceptance, suggesting the potential application of cell morphology disruption in the future freeze-drying industry.

Stability of 20S Proteasome Configurations: Preopening the Axial Gate.

Mass spectrometry studies of the stability of the S. cerevisiae 20S proteasome from 11 to 55 °C reveal a series of related configurations and coupled transitions that appear to be associated with opening of the proteolytic core. We find no evidence for dissociation, and all transitions are reversible. A thermodynamic analysis indicates that configurations fall into three general types of structures: enthalpically stabilized, tightly closed (observed as the +54 to +58 charge states) configurations; high-entropy (+60 to +66) states that are proposed as precursors to pore opening; and larger (+70 to +79) partially and fully open pore structures. In the absence of the 19S regulatory unit, the mechanism for opening the 20S pore appears to involve a charge-priming process that loosens the closed-pore configuration. Only a small fraction (≤2%) of these 20S precursor configurations appear to open and thus expose the catalytic cavity.

Copper nanodot-embedded nitrogen and fluorine co-doped porous carbon nanofibers as advanced electrocatalysts for rechargeable zinc-air batteries

Porous carbon-based electrocatalysts for cathodes in zinc-air batteries (ZABs) are limited by their low catalytic activity and poor electronic conductivity, making it difficult for them to be quickly commercialized. To solve these problems of ZABs, copper nanodot-embedded N, F co-doped porous carbon nanofibers (CuNDs@NFPCNFs) are prepared to enhance the electronic conductivity and catalytic activity in this study. The CuNDs@NFPCNFs exhibit excellent oxygen reduction reaction (ORR) performance based on experimental and density functional theory (DFT) simulation results. The copper nanodots (CuNDs) and N, F co-doped carbon nanofibers (NFPCNFs) synergistically enhance the electrocatalytic activity. The CuNDs in the NFPCNFs also enhance the electronic conductivity to facilitate electron transfer during the ORR. The open porous structure of the NFPCNFs promotes the fast diffusion of dissolved oxygen and the formation of abundant gas-liquid-solid interfaces, leading to enhanced ORR activity. Finally, the CuNDs@NFPCNFs show excellent ORR performance, maintaining 92.5% of the catalytic activity after a long-term ORR test of 20000 s. The CuNDs@NFPCNFs also demonstrate super stable charge-discharge cycling for over 400 h, a high specific capacity of 771.3 mAh g−1 and an excellent power density of 204.9 mW cm−2 as a cathode electrode in ZABs. This work is expected to provide reference and guidance for research on the mechanism of action of metal nanodot-enhanced carbon materials for ORR electrocatalyst design.

Effectively morphology-controlled NiMn layered double hydroxide microflowers by conductive silver nanowires for supercapacitor electrodes

Effective ion and electron transport pathways provide an effective method to further improve the energy storage performance of layered double hydroxide (LDH) for supercapacitors. Here, microflower-like NiMn LDH/silver nanowires (Ag NWs) composites for high-performance supercapacitors are constructed by a convenient hydrothermal method, in which silver nanowires are found to not only ensure excellent electron conductivity but also have a positive effect on the growth of LDH nanosheets to form the unique three-dimensional open pore structure. In addition, the significantly increased interlayer spacing of the composite enables fast ion transport. In particular, NiMn LDH/Ag NWs exhibits higher specific capacitance (1436.30 F·g−1 at 2 A·g−1) in a three-electrode system, which is 121.29% of the specific capacitance of pure NiMn LDH. The asymmetric supercapacitor assembled with NiMn LDH/Ag NWs and AC electrode exhibits high specific capacitance of 215.63 F·g−1 at 2 A·g−1, superior energy density of 71.95 Wh·kg−1 and excellent cycling stability, illustrating that the NiMn LDH/Ag NWs composite is the promising material for supercapacitor applications.

Synthesis of Cellulose-Poly(Acrylic Acid) Using Sugarcane Bagasse Extracted Cellulose Fibres for the Removal of Heavy Metal Ions.

In this study, sugarcane bagasse (SCB) was treated with sodium hydroxide and bleached to separate the non-cellulose components to obtain cellulose (CE) fibres. Cross-linked cellulose-poly(sodium acrylic acid) hydrogel (CE-PAANa) was successfully synthesised via simple free-radical graft-polymerisation to remove heavy metal ions. The structure and morphology of the hydrogel display an open interconnected porous structure on the surface of the hydrogel. Various factors influencing batch adsorption capacity, including pH, contact time, and solution concentration, were investigated. The results showed that the adsorption kinetics were in good agreement with the pseudo-second-order kinetic model and that the adsorption isotherms followed the Langmuir model. The maximum adsorption capacities calculated by the Langmuir model are 106.3, 333.3, and 163.9 mg/g for Cu(II), Pb(II), and Cd(II), respectively. Furthermore, X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectrometry (EDS) results demonstrated that cationic exchange and electrostatic interaction were the main heavy metal ions adsorption mechanisms. These results demonstrate that CE-PAANa graft copolymer sorbents from cellulose-rich SCB can potentially be used for the removal of heavy metal ions.

Lithium extraction from geothermal brine by granulated HTO titanium-based adsorbent with block-co-polymer poly (ethylene-co-vinyl alcohol) (EVAL) as binder

This study reports a novel highly selective H2TiO3 lithium-ion sieve (LIS) based adsorbent spheres using a block-co-polymer poly (ethylene-co-vinyl alcohol) (EVAL) as the binder for selective extraction of lithium from geothermal brine. Combination of the intrinsic hydrophobic/hydrophilic characters of EVAL satisfies the requirement for adsorbent’s robust mechanical strength and access by aqueous brine. Via adjustment of EVAL concentration and the pore former polyethylene glycol (PEG), porous structure as well as the pore connectivity of the spherical EVAL-HTO were well controlled. The adsorption equilibrium, kinetic characteristics, and cycle performance were investigated using a simulated brine with pH adjustment and the real Tibet geothermal brine. The equilibrium adsorption behavior of Li+ on EVAL-HTO showed Langmuir adsorption and the adsorption kinetics conformed to the pseudo-second-order kinetic model. Kinetic analysis using the intra-particular diffusion model confirmed the open porous structure in EVAL-HTO spheres. In real geothermal brine with no pH adjustment, the EVAL-HTO showed adsorption capacity of 11.8 mg/g, slightly below 13.5 mg/g in the simulated brine at pH = 12, but with more stable cycle performance and cost advantage. Excellent selectivity between Li+ and other contaminant ions, except Ca2+, indicated great potential to obtained purified lithium chemicals. Options to remove Ca2+ ions were proposed for future investigation. The results indicate great promise to use EVAL-HTO in lithium adsorption from real geothermal brine.

3D graphene-based active electrodes with large areal capacitance by modified direct ink writing method

The application of 3D printing technology in the field of energy storage is of great practical significance but still remains challenging. Recently, 3D-printed graphene-based architecture has been found to be a promising material for electrochemical energy storage devices. In this study, graphene-based conductive filaments were printed through direct ink writing method (DIW), and then dense poly-pyrrole film (PPy) was formed on the surface of the 3D frame by simple electrodeposition. And followed by post treatment three-dimensional heterogeneous graphene-based electrodes wrapped by nanocarbon cloth (3DCGs) were readily prepared. 3D-printed open porous structure provides effective aligned channels for ion transport as well as large ion accessible area for electrochemical reaction. PPy layer helps to maintain the structural integrity and obtain high capacitance retention rate. A series of 3DCGs with controllable channels were prepared by adjusting the number printing layers, infilled spacing and nozzle size. Thus, we gained an insight into the influence of structural engineering of electrode materials on electrochemical performance. The 5-layer 3DCG with filament spacing of 300 µm and filament diameter of 400 µm achieved an areal capacitance of 2265.19 mF/cm2 at a scan rate of 5 mV/s, which was significantly higher than that of non-3DCG (400.15 mF/cm2). Briefly, this study reports the integration of DIW 3D-printing and electrodeposition techniques allowing a facile way of fabricating customized 3D-electrodes with large areal capacitance.

Preparation of carbon foam from depolymerization-reforming lignin for capacitive deionization

The functionalized utilization of lignin is attracting more and more attention. In this paper, we report a 3D interconnected foamy carbon material with highly open pore structure. The carbon foam is synthesized by depolymerization reforming strategy. The foamy carbon has a deep internal pore channels and exhibits an enhanced electrosorption capacity. The highest desalination of the foamy carbon reaches 30.2 mg·g−1 in 500 mg·L−1 NaCl at 1.2 V with adsorption rate of 3.75 mg/g/min. Meanwhile, the optimal electrode PDLC-1 shows good regeneration capacity. Our work provides a usable way for the preparation of lignin-derived carbon foam with high-performance of capacitive deionization.

Permeability design and assessment of the additively manufactured metal-bonded diamond grinding wheel based on TPMS structures

The development of porous metal-bonded diamond grinding wheel with excellent permeability and satisfying mechanical properties is a huge challenge for traditional manufacturing process. In this paper, a novel design and fabrication method of metal-bonded diamond grinding wheel with human-designed open porous structure is proposed based on triply periodic minimal surfaces (TPMS) and additive manufacturing (AM) process. Darcy’ law and Kozeny-Carman equation are used to calculate the permeability coefficient for the porous grinding wheel. The optimal design method of grinding wheel porous structure is proposed comprehensively considering the geometric characteristic, permeability and mechanical properties. The grinding performance of AM porous grinding wheel is evaluated by BK7 glass grinding experiment. The permeability test result proves the effectiveness of permeability design method for the novel diamond grinding wheel. The grinding test result proves the advantages of the novel diamond grinding wheel.

One Atom Can Make All the Difference: Gas-Induced Phase Transformations in Bisimidazole-Linked Diamondoid Coordination Networks.

Coordination networks (CNs) that undergo gas-induced transformation from closed (nonporous) to open (porous) structures are of potential utility in gas storage applications, but their development is hindered by limited control over their switching mechanisms and pressures. In this work, we report two CNs, [Co(bimpy)(bdc)]n (X-dia-4-Co) and [Co(bimbz)(bdc)]n (X-dia-5-Co) (H2bdc = 1,4-benzendicarboxylic acid; bimpy = 2,5-bis(1H-imidazole-1-yl)pyridine; bimbz = 1,4-bis(1H-imidazole-1-yl)benzene), that both undergo transformation from closed to isostructural open phases involving at least a 27% increase in cell volume. Although X-dia-4-Co and X-dia-5-Co only differ from one another by one atom in their N-donor linkers (bimpy = pyridine, and bimbz = benzene), this results in different pore chemistry and switching mechanisms. Specifically, X-dia-4-Co exhibited a gradual phase transformation with a steady increase in the uptake when exposed to CO2, whereas X-dia-5-Co exhibited a sharp step (type F-IV isotherm) at P/P0 0.008 or P 3 bar (195 or 298 K, respectively). Single-crystal X-ray diffraction, in situ powder XRD, in situ IR, and modeling (density functional theory calculations, and canonical Monte Carlo simulations) studies provide insights into the nature of the switching mechanisms and enable attribution of pronounced differences in sorption properties to the changed pore chemistry.

Injectable, High Specific Surface Area Cryogel Microscaffolds Integrated with Osteoinductive Bioceramic Fibers for Enhanced Bone Regeneration

Organic-inorganic composites with high specific surface area and osteoinductivity provide a suitable microenvironment for cell ingrowth and effective ossification, which could greatly promote bone regeneration. Here, we report gelatin methacryloyl (GelMA) cryogel microspheres that are reinforced with hydroxyapatite (HA) nanowires and calcium silicate (CS) nanofibers to achieve the goal. The prepared composite cryogel microspheres with open porous structure and rough surface greatly facilitate cell anchoring, simultaneously exhibiting excellent injectability. Compared to the only HA- or CS-containing counterparts, the GelMA cryogel microspheres composited with HA:CS (termed as GMHC) achieve sustained release of bioactive Ca, P, and Si elements, which are conducive to osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs). These composite microspheres can prevent from forming peralkalic conditions, which is beneficial for cell growth. After injection of cryogel microspheres into rat calvarial defects, neo-bone tissue grows into their pores, showing tight integration. The embedded bioceramic components significantly promote bone regeneration, with the GMHC achieving the best regenerative outcomes. Promisingly, porous organic-inorganic composite cryogel microspheres, with high specific surface area, biodegradability, and osteoinductivity, can act as injectable microscaffolds to repair bone defects with enhanced efficiency, which may widen the scaffold strategy for bone tissue engineering.