Porous Hollow Research Articles

Simultaneous Determination of Three Food Contaminants in Shrimp Paste by Hollow Porous Pentagonal Au/Ag Alloy Nanotubes with Excellent Sers Activity

Simultaneous Determination of Three Food Contaminants in Shrimp Paste by Hollow Porous Pentagonal Au/Ag Alloy Nanotubes with Excellent Sers Activity

Biological removal of gas‐phase H2S in hollow fibre membrane bioreactors

AbstractBACKGROUNDHydrogen sulphide (H2S) must be treated at its emission source to avoid health risks, odour, and corrosion. Conventional physico‐chemical H2S removal technologies (for example, membrane contactors or chemical scrubbers) have several limitations, such as requiring high amounts of absorption chemicals and energy. In contrast, biological H2S removal technologies are environment friendly, easy to operate, and less expensive due to their low energy requirements. In this study, the feasibility of a porous hydrophilic polyethersulfone hollow fibre membrane bioreactor (HFMB) was tested for the biological removal of gas‐phase H2S by employing three lab‐scale reactors (two biotic and one abiotic). The HFMBs were operated at ~20 °C for ~3 months, employing different H2S inlet loading rates (ILR) and an empty bed residence time of 187 s.RESULTSBiotic performance of the HFMBs demonstrated that the removal efficiency (RE) varied between the different inocula and was in the range of 80–100% for the applied H2S ILR of ~5.0–7.5 g m−3 h−1. The RE reached a constant value of ~100% in both biotic reactors at an ILR of ~17.0 g m−3 h−1 when using acclimatized inoculum. The biotic HFMBs demonstrated ~5–9 times higher H2S flux and ~ 20–26 times higher mass transfer compared to the abiotic control. Surface morphology revealed attached microbial growth on the outer surface of the membranes, while the high throughput sequencing confirmed the richness of H2S oxidizing microbial communities on the shell side.CONCLUSIONThe obtained results confirm that the HFMB configuration is suitable for biological treatment of H2S laden waste gas. © 2021 Society of Chemical Industry (SCI).

Hierarchically porous γ-Ti3O5 hollow nanospheres as an effective sulfur host for long-life lithium-sulfur batteries

Polysulfides shuttle and volume change on cathode seriously degrade the energy density of lithium-sulfur batteries based on sulfur cathodes. Here, we successfully synthesize hierarchically porous γ-Ti3O5 hollow nanospheres (p-Ti3O5) via carbothermal reduction for the first time. The p-Ti3O5 has the feature of large surface area (444.7 m2 g−1), great pore volume (0.89 cm3 g−1), and hierarchical pores. The high electronic conductivity of γ-Ti3O5 phase and chemical interaction between titanium ions and polysulfides are beneficial for ion/electron migration and polysulfide confinement. The unique structure of the obtained p-Ti3O5 ensure sufficient active sites for chemical reaction, provide moving pathways for ion/electron migration, and inhibit structure collapse of cathode electrode during discharge/charge process. When the sulfur cathode is embedded in the p-Ti3O5composite, it provides a reversible discharge capacity of 585 mAh g−1 after prolonged 900 cycles at 0.5C rate with a capacity decay of 0.053% per cycle. It outperforms Ti3O5/S and TiO2/S cathodes on electrochemical performance. Even when sulfur loading is 5.8 mg cm−2, p-Ti3O5/S electrode exhibits a considerable capacity of 5.9 mA h cm−2. This work emphasizes advantages of high conductivity, chemical confinement of polysulfides, and hierarchically porous structure of p-Ti3O5 on sulfur cathode electrode for long-life lithium-sulfur batteries.

Gold-incorporated porous hollow carbon nanofiber for reversible magnesium-metal batteries

Rechargeable magnesium-metal batteries have received ever-increasing attention as potential alternatives to current Li-ion batteries. Although the most relevant studies have mainly focused on exploring compatible electrolyte and cathode materials, relatively less attention has been paid to the development of an efficient anode host. Herein, we propose a unique anode host with a porous hollow carbon nanofiber structure and gold nanoparticles incorporated in the interior (Au@PCNF). Using the dual-nozzle electrospinning technique, a porous web body was configured with the hierarchical network of hollow carbon nanofibers, with the interior of each string specially designed to embed Au nanoparticles. We demonstrated that Au nanoparticles can act as magnesiophilic sites for Mg plating; therefore, we decorated the magnesiophilic seeds inside the hollow nanofibers to efficiently attract newly deposited Mg metal. The unique feature of Au@PCNF not only reduced the nucleation overpotentials for Mg plating but also guided the even deposition of Mg metal on the substrate. As a result, Au@PCNF exhibited stable and long-term cycle performance with enhanced adhesion property for the newly deposited Mg metal compared with other controls. This novel structural design is promising for the development of efficient anode hosts for magnesium-metal batteries, which will help open an avenue for the practical application of multivalent-ion batteries.

Insight into the Supercapacitive Behavior of Activated Hollow Porous Carbon Spheres in Different Electrolytes

Supercapacitive behaviors of the porous carbon electrode principally depend on the properties of electrolyte. In this paper, activated hollow porous carbon spheres (AHPCSs) with large specific areas were prepared by the hydrothermal method and subsequent one-step KOH activation treatment. The electrochemical performances and supercapacitive characteristics of the AHPCS supercapacitors were evaluated in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) ionic liquid electrolyte, 1 mol L–1 LiPF6 organic electrolyte, and 6 mol L–1 KOH aqueous electrolyte. It has been found that the supercapacitors with AHPCS electrode have definitely good supercapacitive behaviors in the three electrolytes. Especially, the AHPCS supercapacitor in the EMIMBF4 ionic liquid electrolyte that has a wide operating voltage of 0–3.0 V exhibits an excellent rate performance with capacitance retention of 72.3% from 0.5 to 10 A g–1 and a good cycle performance with a high capacitance retention of 94.2% after 4000 consecutive cycles. Moreover, it obtains a high energy density of 80.5 Wh kg–1 at 750 W kg–1, which transcends most of the currently reported carbon-based supercapacitors. Therefore, the supercapacitors with EMIMBF4 ionic liquid as electrolyte and AHPCSs as active electrode materials show tremendous potential in terms of boosting comprehensively electrochemical performance.

Porous ZnMn2O4 hollow microrods: Facile construction and excellent electrochemical performances for lithium ion batteries

Porous ZnMn2O4 hollow microrods have been constructed through a facile co-precipitation method followed by an annealing process. The plausible formation mechanism for the unique architecture of ZnMn2O4 microrods was proposed and discussed in detail. It is found that the calcination temperature plays a key role in determining the microstructures of ZnMn2O4. On the whole, 700 °C is the optimal temperature, which not only makes the as-constructed ZnMn2O4 microrods (denoted as ZMO-700) the porous and hollow architecture, but also owns a good crystallinity, high porosity and large specific surface area. When used as anode materials for lithium ion batteries, the ZMO-700 exhibits outstanding electrochemical performances. It both possesses a high reversible capacity of 902 mAh g−1 after 320 cycles at 0.5 C, and presents an excellent rate capability in the current rate region of 0.1–5 C, especially deliveries a high capacity of 223 mAh g−1 at 5 C. The significant enhancement in the electrochemical performances should be attributed to the synergistic effect of the porous hollow architecture and the micro-nano hierarchical structure for the as-constructed ZnMn2O4 anode.

High-flux CO2-stable oxygen transport hollow fiber membranes through surface engineering

The influences of bulk diffusion and surface exchange on oxygen transport of (La0.6Ca0.4)(Co0.8Fe0.2)O3-δ (LCCF) hollow fiber membranes were investigated. As an outcome, two strategies for increasing the oxygen permeation were pursued. First, porous LCCF hollow fibers as support were coated with a 22 μm dense LCCF separation layer through dip coating and co-sintering. The oxygen permeation of the porous fiber with dense layer reached up to 5.10 mL min−1 cm-2 at 1000 °C in a 50 % CO2 atmosphere. Second, surface etching of dense LCCF hollow fibers with H2SO4 was applied. The surface etching of both inner and outer surfaces leads to a permeation improvement up to 86.0 %. This finding implies that the surface exchange reaction plays a key role in oxygen transport through LCCF hollow fibers. A good long-term (>250 h) stability of the asymmetric hollow fiber in a 50 % CO2 atmosphere was found at 900 °C.

Isolated Single-Atom Ni-N5 Catalytic Site in Hollow Porous Carbon Capsules for Efficient Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries suffer from multiple complex and often interwoven issues, such as the low electronic conductivity of sulfur and Li2S/Li2S2, shuttle effect, and sluggish electrochemical kinetics of lithium polysulfides (LiPSs). Guided by theoretical calculations, a multifunctional catalyst of isolated single-atom nickel in an optimal Ni-N5 active moiety incorporated in hollow nitrogen-doped porous carbon (Ni-N5/HNPC) is constructed and acts as an ideal host for a sulfur cathode. The host improved electrical conductivity, enhanced physical-chemical dual restricting capability toward LiPSs, and, more importantly, boosted the redox reaction kinetics by the Ni-N5 active moiety. Therefore, the Ni-N5/HNPC/S cathode exhibits superior rate performance, long-term cycling stability, and good areal capacity at high sulfur loading. This work highlights the important role of the coordination number of active centers in single-atom catalysts and provides a strategy to design a hollow nanoarchitecture with single-atom active sites for high-performance Li-S batteries.

Improved Gas-Sensitive Properties by a Heterojunction of Hollow Porous Carbon Microtubes Derived from Sycamore Fibers

Improved Gas-Sensitive Properties by a Heterojunction of Hollow Porous Carbon Microtubes Derived from Sycamore Fibers

Regulation of Sulfur doping on rational synthesized porous hollow carbon spheres and their superior electromagnetic wave attenuation performance

Recently, developing an ideal electromagnetic wave (EM) absorption material, which can simultaneously possess the good abilities of EM energy dissipation, chemical stability and lightweight, has attracted significant attention. Herein, rational designed porous hollow carbon spheres have been prepared via a controllable chemical etching process and followed by a regulated sulfur doping process in the carbon frameworks. The content of sulfur doping can be exactly tuned by simplify adjusting the amount of thioacetamide during the reaction in which can effectively achieve the good balance between the impedance matching and dielectric loss. Benefiting from the porous hollow structure, good impedance matching condition and high dielectric loss, the as-prepared sulfur-doped porous hollow spheres (HCSs) could obtain an efficiency EM attenuation performance, with a maximum effective absorption bandwidth (ƒE) of 6.7 GHz at an absorbent thickness of 2.0 mm. When the matching thickness was only 1.65 mm, the minimum reflection loss (RL) value reached − 53 dB. Therefore, this work confirms that the sulfur-doped porous hollow carbon spheres are expected to be reliable microwave attenuation materials, which also opens up a potential strategy for design and synthesis of high-performance carbon-based materials with tunable EM properties.

Facile preparation of porous hollow CoxMn3-xO4 normal-reverse coexisted spinel for toluene oxidation

A facile method for the preparation of porous hollow CoxMn3-xO4 normal-reverse coexisted spinel is developed. The CoxMn3-xO4 catalysts with different morphologies can be prepared via adjusting the Co/Mn molar ratio using mixed carbonates as the precursors. The as-prepared CoxMn3-xO4 catalysts exhibit excellent catalytic activities for toluene oxidation due to the synergistic effect of abundant oxygen vacancies and the optimal molar ratio of Co3+/Mn2+–Co2+/Mn3+ coupled redox ion pairs. The porous hollow hierarchical structure of CoxMn3-xO4 is conducive to maintain good long-term structural stability and activity stabilities. The catalytic activity of CoxMn3-xO4 shows no significant loss during the 100 h of on-stream stability test and the 5 vol% water vapor inhibition test, showing excellent anti-sintering ability, high-efficiency mass transfer ability and anti-moisture ability.

ZIF-8@ZIF-67-Derived Co Embedded into Nitrogen-Doped Carbon Nanotube Hollow Porous Carbon Supported Pt as an Efficient Electrocatalyst for Methanol Oxidation.

It is of prime importance to develop anode electrocatalysts for direct methanol fuel cells (DMFCs) with good performance, which is critical for their commercial applications. Metal-organic framework (MOF)-derived carbon materials are extensively developed as supports of catalysts. Herein, Co embedded nitrogen-doped carbon nanotube hollow porous carbon (Co-NCNT-HPC) derived from MOFs have been fabricated, which were synthesized by pyrolyzing at an optimized temperature of 800 °C using ZIF-8@ZIF-67 as a precursor. The presence of ZIF-8@ZIF-67 ensures the doping of nitrogen and the large specific surface area of the support materials at high temperatures. A Pt/Co-NCNT-HPC800 sample, which was synthesized using Co-NCNT-HPC800 as a support, showed an enhanced mass activity of 416.2 mA mg−1Pt for methanol oxidation reaction (MOR), and the onset potential of COad oxidation of 0.51 V, which shifted negatively about 0.13 V compared with Pt/C (20%). Moreover, the Pt/Co-NCNT-HPC800 sample exhibits high stability. This work provides a facile strategy for MOF-derived carbon materials to construct advanced electrocatalysts for MOR.

Modeling a Free Burnishing of a Powder Hollow Cylinder

The paper presents the results of the computer modelling of the stressed state and relative density when burnishing a porous hollow cylinder, made from copper sintered powder material. The mathematical model, based on the theory of porous bodies’ plasticity, is used for the analysis. The paper researches the impact of the initial porosity of the material on the effective stresses distribution, relative density and force change when free burnishing of hollow cylinders. It is ascertained that with the decrease of the initial porosity of the sintered material there is the increase of the burnishing force, stresses rate and relative density on the inner sur-face of a hollow cylinder. For porous materials at a certain stage of burnishing, the deformation zone is transformed into the compaction zone with a high relative density which de-creases while moving away from the inner surface of hollow cylinders. The maximum value of the relative density is implemented directly on the inner surface of hollow cylinders; along with this the density value is evenly distributed on the inner wall.

N, Se doped flower-shaped hollow carbon spheres to enhance performance in supercapacitor

Designing energy storage devices assembled with precious metal-free active materials is the key to developing a low-carbon economy and sustainable energy supply. Therefore, we take Se as the guest and porous nitrogen-modified flower-shaped hollow carbon spheres (NFHC) as the main body to form Se-NFHC. The performance as an active material in supercapacitors is explored. The results show that the specific capacitance of the material reaches 774 F g−1, and after 6000 constant current charge–discharge tests, it can still maintain 95.4% specific capacitance, which provides selectivity for materials in the field of energy storage.

Facile Synthesis of Porous Hollow Cobalt‐Doped λ‐MnO2 Nano Architectures as a High‐performance Anode Material for Li‐ion Batteries and Li‐ion Hybrid Supercapacitors

AbstractThe cost‐effectiveness and easy availability of MnO2 have attracted researchers′ attention as an anode electrode for LIBs over other transition metal oxides. However, MnO2 usage has been limited to its low reaction reversibility and poor conversion kinetics. Besides, Li‐ion hybrid supercapacitors (LiHSCs) are in urgent demand which offers higher power densities than LIBs without compromising energy density. Among different polymorphs of MnO2, λ‐MnO2, due to its 3D spinel structure, can be applied in many applications. Usually, λ‐MnO2 can be obtained by extracting lithium from LiMn2O4 using complex electrochemical or acid leaching methods. This study presents a modified Li2O2 assisted method to obtain cobalt‐doped 3D architectures of λ‐MnO2 porous hollow nanostructures. The resultant MnxCo1‐xOy hollow structures with 5 % cobalt addition are used as anode for LIBs exhibited excellent charge reversibility and cycle stability over thousands of reaction cycles. This result is known to be one of the finest among MnO2 anodes reported to date. Also, a LiHSC device is fabricated with MnxCo1‐xOy hollow structures as anode and the device exhibits an excellent comprehensive electrochemical performance in terms of high operating voltage (4.2 V), with a specific cell capacity of 33 mAh g−1 at a high current density of 5 A g−1 and achieved the maximum power density of 12261 W kg−1 (with energy density at 81.7 Wh kg−1) with long cycle life.

Copper atoms inlaid in titanium zirconium oxide spherical shell confine free radicals for the robust Fenton-like treatment of complex biogas slurry

A novel Fenton-like system based on single-atom catalysts was developed for the treatment of biogas slurry under 90 °C conditions. First, a binary composite was synthesized in which porous TiZrO4 hollow spheres provided sites for embedding Cu atoms and confining generated free radicals to promote the efficiency of oxidation reactions. The TiZrO4/Cu catalyst mediated the simultaneous oxidation of approximately 69 % of the chemical oxygen demand and at least 55 % of total nitrogen in biogas slurry within 1 h, and the residual organics, including simple acetic acid and propionic acid, possessed high biodegradability. Correspondingly, all of the fluorescent fulvic acids, proteins, polysaccharides, and humic acids disappeared. DFT calculations further confirmed that the electron-rich single Cu atoms generated hydroxyl radicals by capturing and reducing H2O2, thus improving the treatment efficiency. The special catalyst structure with dispersed Cu atoms maintained excellent catalytic activity and durability with negligible Cu leakage over multiple cycles.

The Enhanced Hydrogen Storage Capacity of Carbon Fibers: The Effect of Hollow Porous Structure and Surface Modification

In this study, highly porous carbon fiber was prepared for hydrogen storage. Porous carbon fiber (PCF) and activated porous carbon fiber (APCF) were derived by carbonization and chemical activation after selectively removing polyvinyl alcohol from a bi-component fiber composed of polyvinyl alcohol and polyacrylonitrile (PAN). The chemical activation created more pores on the surface of the PCF, and consequently, highly porous APCF was obtained with an improved BET surface area (3058 m2 g−1) and micropore volume (1.18 cm3 g−1) compare to those of the carbon fiber, which was prepared by calcination of monocomponent PAN. APCF was revealed to be very efficient for hydrogen storage, its hydrogen capacity of 5.14 wt% at 77 K and 10 MPa. Such hydrogen storage capacity is much higher than that of activated carbon fibers reported previously. To further enhance hydrogen storage capacity, catalytic Pd nanoparticles were deposited on the surface of the APCF. The Pd-deposited APCF exhibits a high hydrogen storage capacity of 5.45 wt% at 77 K and 10 MPa. The results demonstrate the potential of Pd-deposited APCF for efficient hydrogen storage.

ZnO@zeolitic imidazolate frameworks derived porous hybrid hollow carbon shell as an efficient electrocatalyst for oxygen reduction

ZnO@zeolitic imidazolate frameworks derived porous hybrid hollow carbon shell as an efficient electrocatalyst for oxygen reduction

Facile preparation of ultralight porous carbon hollow nanoboxes for electromagnetic wave absorption

Strong absorption, thin thickness, low density and broad band are ideal characteristics of electromagnetic wave absorption (EWA) materials. In this work, ultralight porous carbon hollow nanoboxes (PCHN), which have low density and high specific surface area, are successfully prepared by the vapor deposition and etching process. Excellent EWA performances are achieved in the filler with only 3 wt%. A minimum reflection loss (RLmin)value of −30.46 dB (2.2 mm) along with an efficient absorption bandwidth (EAB) (RL ≤ −10 dB) of 5.44 GHz is achieved. And the EAB (RL ≤ −20 dB, corresponding to 99% absorption) can be tuned in the frequency band of 4.88–17.04 GHz via adjusting the thickness from 6.0 to 1.9 mm. The excellent EWA performance is attributed to conduction loss, interfacial polarization, and good impedance matching. Moreover, the adjacent carbon micro-sheets can provide multiple positions for EW reflection, which prolongs the propagation paths of EW and is conducive to the consumption of EW energy. The light weight, broad band and superior RLmin value make the as-prepared PCHN promising candidates for practical EWA applications.

Techno-economics and sensitivity analysis of hybrid process combining carbon molecular sieve membrane and distillation column for propylene/propane separation

The conceptual designs of a carbon molecular sieve (CMS) membrane and a distillation process with heat pump integration were used to evaluate propylene/propane separation system economics. A CMS membrane prepared on a porous alumina hollow fiber was employed to establish the conceptual design of the integrated system. The technologies were evaluated in terms of capital and operating costs and compared to a conventional C3-splitter to elicit the one that minimizes total costs. Different configurations are suggested to satisfy the design specifications of 99.6 wt% product purity and 99% propylene recovery rate. When the heat pump with membrane system was applied in condition of stage cut 0.5, pressure ratio 3, propylene/propane selectivity 28, and propylene permeance 20 GPU, the capital and operating costs decreased by 2.3% and 68.7% compared to distillation only process, respectively. The cost saving variation of the hybrid system was confirmed with membrane specifications such as selectivity and permeance. The simulation results indicated that the heat pump with membrane process is advantageous in terms of both energy and economic savings. A correlation contour between membrane permeance/selectivity and cost saving was developed for the hybrid systems. The findings provide a helpful guide to more economically separate gas mixtures.