SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Porous media

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A series of amorphous 3D Co-based phosphate networks with hierarchical porosity, including the CoPi, the binary CoM1 Pi and the trinary CoM1 M2 Pi (Mi  = NiII , FeIII , CeIII ) are produced via a novel bitemplate coprecipitation approach at room temperature. Interestingly, the integration of FeIII and CoII in the same network is found to significantly influence both the porosity and the electronic state of CoII . The CoFePi with a FeIII to CoII mole ratio of 0.91 has a specific surface area of 170 m2 g-1 and average pore size of 12.3 nm, larger than those of the CoPi network; furthermore, the CoII within such CoFePi exhibits a higher oxidation state than that in the CoPi. Due to such structural and compositional merits, the binary CoFePi network shows superior oxygen evolution reaction (OER) electrocatalytic activity, which gives an overpotential as low as 0.315 V at 10 mA cm-2 and a Tafel slope of 33 mV dec-1 in 0.10 m KOH. Additionally, the trinary CoFeNiPi demonstrates similar OER catalytic performance. The two phosphate networks also exhibit remarkable catalytic stability. In view of their easy preparation, superior activity, high stability, and low cost, such transition metal phosphate networks are promising catalysts for practical OER processes.

Concepts: Oxygen, Chemical reaction, Hydrogen, Electrochemistry, Oxide, Specific surface area, Porous media, Tafel equation

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Infiltration systems are treatment technologies based on water percolation through porous media where biogeochemical processes take place. Grain size distribution (GSD) acts as a driver of these processes and their rates, as well as it influences nutrient accumulation in sediments. Coarse sands inhibit anaerobic reactions such as denitrification and could constrain nutrient accumulation in sediments due to smaller specific surface area. On the other hand, fine sands provide higher nutrient accumulation but need a larger area available to treat the same volume of water; furthermore they are more susceptible to bio-clogging. Combining both sand sizes in a bilayer system would allow infiltrating greater volume of water and the occurrence of aerobic/anaerobic processes. We studied the performance of a bilayer coarse-fine system compared to a monolayer fine one -by triplicate- in an outdoor infiltration experiment to close the C-N-P cycles simultaneously in terms of mass balances. Our results confirm that the bilayer coarse-fine GSD promotes nutrient removal by physical adsorption and biological assimilation in sediments, and further it enhances biogeochemical process rates (two-fold higher than the monolayer system). In overall, the bilayer coarse-fine system allows treating larger volume of water per surface unit achieving similar removal efficiencies as the fine system.

Concepts: Adsorption, Hydrogeology, Area, Specific surface area, Surface chemistry, BET theory, Sand, Porous media

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The climate change and energy crisis promote the rapid development of electrochemical energy-storage devices. Of many intriguing physicochemical properties such as excellent chemical stability, high electronic conductivity and large specific surface area, porous carbon materials have always been considering as a promising candidate for electrochemical energy storage. Up to date, a wide variety of porous carbon materials upon molecular design, pore control and compositional tailoring have been proposed for energy-storage applications. This focus review summaries recent advances in the synthesis of various porous carbon materials from the view of energy storage, especially in the past three years. Their applications in representative electrochemical energy storage devices like lithium-ion batteries, supercapacitors, lithium-ion hybrid capacitors have been discussed in this review, looking forward to offering some inspirations and guidelines for the exploitation of advanced carbon-based energy-storage materials.

Concepts: Climate change, Physical chemistry, Materials science, Battery, Rechargeable battery, Capacitor, Specific surface area, Porous media

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In this work, bamboo charcoal was used as solid-phase extraction adsorbent for the enrichment of six perfluoroalkyl acids (PFAAs) in environmental water samples before liquid chromatography-tandem mass spectrometry analysis. The specific porous structure, high specific surface area, high porosity, and stability of bamboo charcoal were characterized. Several experimental parameters which considerably affect extraction efficiency were investigated and optimized in detail. The experimental data exhibited low limits of detection (LODs) (0.01-1.15 ng/L), wide linear range (2-3 orders of magnitude and R ≥ 0.993) within the concentration range of 0.1-1000 ng/L, and good repeatability (2.7-5.0%, n = 5 intraday and 4.8-8.3%, n = 5 interday) and reproducibility (5.3-8.0%, n = 3). Bamboo charcoal was successfully used for the enrichment and determination of PFAAs in real environmental water samples. The bamboo charcoal-based solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry analysis possessed great potential in the determination of trace PFAA levels in environmental water samples.

Concepts: Mass spectrometry, Water, Porosity, Liquid chromatography-mass spectrometry, Specific surface area, Surface chemistry, BET theory, Porous media

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Flexible highly porous Fe2O3 and V2O5 nanofibers are synthesized by a facile electrospinning method followed by calcination treatment and directly used as binder-free electrodes for high-performance supercapacitors. These Fe2O3 and V2O5 nanofibers interconnect with each other and construct three-dimensional hierarchical porous films with high specific surface area. Benefiting from the unique structural features, the intriguing binder-free Fe2O3 and V2O5 porous nanofiber electrodes possess high specific capacitance of 255 F g-1 and 256 F g-1 at 2 mV s-1 in 1 M Na2SO4 electrolyte, respectively. An all-solid-state asymmetric supercapacitor is fabricated using Fe2O3 and V2O5 nanofibers as negative and positive electrodes, respectively, and the all-solid-state asymmetric supercapacitor can be operated up to 1.8 V attributed to the wide and opposite potential window of both electrodes. The assembled all-solid-state asymmetric supercapacitor achieves a high energy density up to 32.2 Wh kg-1 at an average power density of 128.7 W kg-1 as well as excellent cycling stability and power capability. The effective and facile synthesis method and superior electrochemical performance provided in this work make electrospun Fe2O3 and V2O5 nanofibers promising electrode materials for high performance asymmetric supercapacitors.

Concepts: Cathode, Electrochemistry, Electrolyte, Electrode, Rechargeable battery, Energy density, Specific surface area, Porous media

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A piezoresistive sensor based on the ultralight and superelastic aerogel is reported to fabricate MXene/Reduced graphene oxide (MX/rGO) hybrid 3D structure and utilize their pressure-sensitive characteristics. The MX/rGO aerogel not only combines the rGO’s large specific surface area and the MXene’s (Ti3C2Tx) high conductivity but also exhibits rich porous structure, which leads to better performance than single component rGO or MXene in terms of the pressure sensor. And the large nanosheets of rGO can prevent the poor oxidization of MXene by wrapping MXene inside the aerogel. More importantly, the piezoresistive sensor based on MX/rGO aerogel shows extremely high sensitivity (22.56 kPa-1), fast response time (< 200 ms) and good stability over 10,000 cycles. The piezoresistive sensor based on MX/rGO hybrid 3D aerogel can easily capture the signal below 10 Pa, thus clearly test the pulse of an adult at random. Based on its superior performance, it also demonstrates potential application in measuring pressure distribution, distinguishing subtle strain, monitoring healthy activity and so on.

Concepts: Pressure, Specific surface area, Surface chemistry, Porous media

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Mesoporous carbon can be synthesized with good control of surface area, pore-size distribution, and porous architecture. Although the relationship between porosity and supercapacitor performance is well known, there are no thorough reports that compare the performance of numerous types of carbon samples side by side. In this manuscript, we describe the performance of 13 porous carbon samples in supercapacitor devices. We suggest that there is a “critical pore size” at which guest molecules can pass through the pores effectively. In this context, the specific surface area (SSA) and pore-size distribution (PSD) are used to show the point at which the pore size crosses the threshold of critical size. These measurements provide a guide for the development of new kinds of carbon materials for supercapacitor devices.

Concepts: Petroleum, Specific surface area, Surface chemistry, Flywheel energy storage, Porous media

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3D magnetic hollow porous CdFe2O4microspheres (3D MHPS-CdFe2O4) were prepared by a one-step and template-free hydrothermal method. The material was applied for magnetic solid phase extraction of three azo colorants (Acid Red, Congo Red, Sunset Yellow). Compared to conventional CdFe2O4nanoparticles, the new 3D material exhibits superior extraction capability because of its unique hollow porous structure, high specific surface area, and the strong interaction between 3D microspheres and the colorants. A magnetic solid phase extraction (MPSE) combined with HPLC was established for simultaneous detection of the three azo colorants in food samples. Under optimum conditions, the detection limits are 0.54-1.00 ng mL-1, and good recoveries of 87.0-100.7% were obtained with spiked samples, with relative standard deviation of ≤ 3.8%. The combination of using the new 3D material and MPSE-HPLC results in an efficient, sensitive and inexpensive method for simultaneous determination of such colorants. Graphical abstract Schematic of the preparation of 3D magnetic hollow porous CdFe2O4microspheres as solid phase extractant for simultaneous trace detection of three azo colorants in real samples.

Concepts: Fundamental physics concepts, Condensed matter physics, Analytical chemistry, Specific surface area, Azo dyes, Phases of matter, Porous media, Solid phase extraction

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As the most important components of a hemodialysis device, nanofibrous membranes enjoy high interconnected porosity and specific surface area as well as excellect permeability. In this study, a tubular nanofibrous membrane of polysulfone nanofibers was produced via electrospinning method to remove urea and creatinine from urine and blood serums of dialysis patients. Nanofibrous membranes were electrospun at a concentration of 11.5 wt% of polysulfone (PS) and dimethylformamide (DMF)/tetrahydrofuran (THF) with a ratio of 70/30. The effects of the rotational speed of collectors, electrospinning duration, and inner diameter of the tubular nanofibrous membrane on the urea and creatinine removal efficiency of the tubular membrane were investigated through the hemodialysis simulation experiments. It was found that the tubular membrane with an inner diameter of 3 mm elecrospun at shorter duration with lower collecting speed had the highest urea and creatinine removal efficiency. The hemodialysis simulation experiment showed that the urea and creatinine removal efficiency of the tubular membrane with a diameter of 3 mm were 90.4 and 100%, respectively. Also, three patients' blood serums were tested with the nanofibrous membrane. The results showed that the creatinine and urea removal rates were 93.2 and 90.3%, respectively.

Concepts: Dialysis, Specific surface area, Surface chemistry, Porous media

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Multi-shell, stable, porous metal-oxide microspheres (Ni-Co oxides, Co3O4 and NiO) have been synthesized through amorphous-coordination-polymers based self-templated method. Both oxides of Ni and Co show poor selectivity to xylene, but the composite phase has substantial selectivity (eg. Sxylene/Sethanol = 2.69), and remarkable sensitivity (11.5 to 5 ppm xylene at 255 oC). The short response and recovery times (6 and 9 seconds), excellent humidity-resistance performance (with coefficient of variation = 11.4 %), good cyclability and long-term stability (sensitivity attenuation of ~9.5% after 30 days; stable sensitivity thereafter) all show that this composite is a competitive solution to the problem of xylene sensing. The sensing performances are evidently due to the high specific surface area and the nano-heterostructure in the composite phase.

Concepts: Specific surface area, Surface chemistry, Porous media