Porous Spheres Research Articles

Sulfur atom modulated Fe-Nx species embedded in hollow porous carbon spheres for efficient oxygen reduction and high-performance zinc-air batteries

A nitrogen (N) and sulfur (S) co-doped FeS/FeN-NC-X4 (X represents the molar ratio of Fe and S added) catalyst with an abundant S-doped Fe-Nx species is designed rationally for enhanced oxygen reduction reaction (ORR). And these valuable activation sites are embedded into a hollow porous carbon shell for increasing the limiting current density and increasing the onset potential. The precise regulation of the Fe/S ratio also highlights the influence of appropriate S doping on the catalytic performance of atomically dispersed Fe–N–C-based catalysts for high-performance Zinc-air batteries. All of these factors contribute to the remarkable catalytic performance of FeS/FeN-NC-X4 for the ORR with a half-wave potential of 0.863 V, which is superior to most non-precious metal catalysts previously reported. Simultaneously, the synthesized material is used as a cathode catalyst to assemble zinc-air batteries to illustrate its practical application. The results show that it has a high open-circuit voltage (1.44 V), extremely high maximum power density (156 mW cm−2) and excellent stability (stable operation for 400 h at a current density of 5 mA cm−2). The assembled portable and flexible batteries also have a high open circuit voltage of 1.40 V and a maximum power density of 68.1 mW cm−2. This work therefore presents a new method for the synthesis of atomically dispersed iron catalysts with high efficiency and metal content that are appropriate for practical energy storage applications.

Enzyme-immobilized Screen-printed Sensor for One Drop of Sample Using Porous Silica Spheres

Enzyme-immobilized Screen-printed Sensor for One Drop of Sample Using Porous Silica Spheres

Electrochemical Sensing Based on Metal-Organic Frameworks-Derived Carbon/Molybdenum Disulfide Composites with Superstructure and Synergistic Catalysis.

Metal-organic frameworks (MOFs)-derived nanocomposite has attracted extensive attention due to its tunable nanoscale cavities and high chemical tailorability. Herein, with the aim of developing a sensitive electrochemical sensor for p-nitrophenol, a novel MOFs-derived nanocomposite was prepared by the solvothermal method using Zr-MOFs, thiourea, and sodium molybdate as raw materials. By controlling the growth mode and reaction time, the nanohybrids displayed a superstructure composed of MOFs-derived carbon (MOFs-C) and MoS2. Scanning electron microscopy images indicated that MOFs-C/MoS2 was a flower-like porous sphere. Transmission electron microscopic images showed that the MOFs-C/MoS2 had a unique arrow target-like structure. The porous structure held great promise for the fast mass transfer into the material, while the layer-by-layer distributed carbon and MoS2 provided a great structure for the synergistic catalysis. The electrochemical oxidation of (hydroxyamino)phenol to nitrosophenol, which is an important process for the electrochemical behavior of p-nitrophenol, can be selectively catalyzed by the MOFs-C/MoS2. Therefore, the electrochemical sensor based on the MOFs-C/MoS2 material exhibited excellent analytical performance in the determination of p-nitrophenol. Using the technique of square wave voltammetry, the peak current varied quantitatively with the presence of p-nitrophenol in the wide concentration range of 0.5-500 μM. Furthermore, the electrochemical sensor exhibited good practicability in real sample analysis.

Ultrafine Ni0.85Se nanoparticles encapsulated inside hollow porous carbon spheres and their excellent Na storage performance

As a novel anode material for sodium-ion batteries, ultrafine Ni0.85Se nanoparticles encapsulated inside hollow porous carbon spheres (HPCS@Ni0.85Se) are prepared by impregnating Ni(NO3)2 into HPCSs, calcination and selenization, which is based on the strong capillary effect of HPCSs. Material characterization reveals that Ni0.85Se nanoparticles with a diameter of 5–15 nm are evenly dispersed and intimately coupled to the internal wall of HPCSs, and the content of Ni0.85Se reaches 52.81%. HPCSs as unique reactors and Ni0.85Se carriers improve electronic conductivity of Ni0.85Se, facilitate electrolyte penetration and storage, buffer volume variation of Ni0.85Se, effectively confine Ni0.85Se during long-term cycles. Consequently, HPCS@Ni0.85Se exhibits excellent cycling durability and extraordinary rate capability. High reversible capacities of 341 mA h g−1 at 1 A g−1 after 1000 cycles, 280 mA h g−1 at 5 A g−1 after 2000 cycles and 305 mA h g−1 at 10 A g−1 after 540 cycles are achieved. The reaction kinetics and Na + storage mechanism are further analyzed by galvanostatic intermittent titration technique, cyclic voltammetry and electrochemical impedance spectra measurements. Ex-situ characterizations confirm outstanding structural stability of HPCS@Ni0.85Se. It is demonstrated that HPCS@Ni0.85Se is an excellent anode material, and this unique HPCS-based nanoencapsulation structure is an effective composite strategy for transition metal selenides.

Synthesis of mesoporous carbon particles with different pore sizes by soft template method

The Stöber method provides a facile procedure for making carbon spheres with controlled particle sizes and is considered to be low-cost. In this study, a facile method has been established for synthesizing porous carbon spheres with variable pore sizes using a modified Stöber process. The influence of acid treatment and manipulating the carbonization process heating rate on the pore size and morphology of the particles was investigated by nitrogen adsorption, Scanning Electron Microscopy (SEM), Powder X-ray diffraction (XRD), Raman and Fourier Transform Infrared Spectroscopy (FTIR). According to the results, carbon spheres were in the size range between 1 and 7 microns. Pore size characterization shows that the pore diameter has increased by increasing the heating rate as well as by performing acid treatment. Tunable pore sizes from 2.25 to 8 nm have been evidenced by the experiments. These synthesized mesoporous carbons with different pore sizes which facilitate penetration of molecules and ions are promising as effective materials for adsorption, encapsulation and material delivery applications.

Bamboo fiber-derived porous carbon microspheres decorated with MnO2 for enhanced supercapacitor performance

Manganese dioxide holds great potential as a pseudocapacitive material for supercapacitors. However, its limited electrical conductivity hampers the realization of its theoretically predicted capacitance. In this study, we successfully synthesized MnO2 in-situ on porous carbon microspheres derived from bamboo pulp fibers using a hydrothermal method. The morphology and phase of MnO2 were controlled by adjusting reduction reaction of KMnO4. Porous carbon spheres coated with sheet-like δ-MnO2 were obtained at a low Mn/C ratio, resulting in an impressive specific surface area of 401.4 m2 g−1. The composite exhibited remarkable specific capacitance of 364.4 F g−1 at a current density of 0.5 A g−1 and exhibited excellent capacitance retention of 99.7 % after undergoing 10,000 cycles. Incorporation of MnO2 improved the capacitance performance of porous carbon spheres by 81 %. This study presents promising prospects for the sustainable and environmentally friendly production of bamboo-derived carbon composite materials for supercapacitors.

Achieving High-Rate and Durable Sodium Storage through Confined Construction of NiSe2 Particles Embedded in Porous N-Doped Carbon Spheres

Achieving High-Rate and Durable Sodium Storage through Confined Construction of NiSe₂ Particles Embedded in Porous N-Doped Carbon Spheres

Preparation and characterization of high catalytic performance supported TS-2 zeolites for phenol hydroxylation

Good inter-grown TS-2 zeolites layer is successfully prepared on the outer surface of porous millimeter α-Al2O3 sphere by secondary hydrothermal synthesis. The supported TS-2 zeolites are loaded into a fixed-bed catalytic reactor for catalyzing phenol hydroxylation by hydrogen peroxide, which could efficiently avoid the fussy separation process. Influences of synthesis parameters on Ti active micro-environment, crystal morphology and catalytic performance of the supported TS-2 zeolites are investigated in this work, medium isopropanol content is necessary for preparing fine and homogenous TS-2 zeolites layer on the porous α-Al2O3 sphere. Besides, formation process of the supported TS-2 zeolites is studied in this study, which divided into three stages, dissolution of seed crystals, formation of novel nuclei, growth and aggregation of TS-2 zeolites layer. When the titanium source, isopropanol/SiO2 and TiO2/SiO2 molar ratio of the initial synthesis gel are tetrabutyl titanate, 1.0 and 0.035, tetra-coordinated titanium containing and compact TS-2 zeolites layer are fully covered on the α-Al2O3 sphere, the optimum phenol conversion and dihydroxybenzene selectivity of the zeolites are 40.07% and 98.52% at 65 °C.

Preparation of porous carbon spheres by templated self-assembly for rapid hemostasis

Porous carbon spheres (PCS) with different specific surface areas and porous structures were prepared by templated self-assembly method. The as-prepared PCS had uniform radically distributed channels, single cavity and dispersed dendritic pore structures respectively. The whole blood clotting time tests showed the good hemostatic properties of PCS, even better than Celox. It's probably the specific surface area made the difference over the hemostatic performance of PCS. The possible reason is that the higher specific surface area can increase the contact area between PCS and blood, promote blood coagulation rapidly. And the oxygen polar functional groups on the surface of PCS can rapidly stimulate platelets and red blood cells when in contact with blood. Both of the hemolysis rate and cell viability experiments proved that PCS had good biocompatibility. The hemostatic effect of PCS in vivo were preliminary validated on the mouse tail-cutting model and the rabbit liver injury model, and all PCS could efficiently control the caudal and hepatic hemorrhage. Especially, PCSF127 with a pore size of 3 nm and specific surface area of 335 m2 g−1 showed the best hemostatic efficiency, and it was expected to be an ideal candidate for rapid hemostasis in the battlefield or pre-hospital.

Realizing optimized interfacial polarization and impedance matching with CNT-confined Co nanoparticles in hollow carbon microspheres for enhanced microwave absorption

The hollow porous structure with exceptional interfacial effect and customizable internal environment shows significant potential for application as electromagnetic shielding and absorption materials. However, designing hollow porous electromagnetic absorbers with both desirable impedance matching and high loss capability remains a challenge. Herein, 3D hollow porous electromagnetic microspheres were constructed by assembling 0D Co magnetic nanoparticles, 1D carbon nanotubes, and 2D carbon nanosheets. Due to the sufficient sites for Co2+ riveting, the high loading of magnetic carbon nanotubes (CoNC) and porous carbon spheres formed high-density interfaces, enhancing the interfacial polarization. Furthermore, high-density CoNC were grown in situ on the hollow porous carbon (HPC) microsphere, forming a highly dispersed 3D magnetic network that inhibited the aggregation of magnetic nanoparticles and enhanced magnetic coupling. Therefore, the as-prepared CoNC/HPC microspheres exhibited excellent microwave absorption (MA) performance, with a minimum reflection loss of -33.2 dB and an effective bandwidth of 5.5 GHz at a thickness of only 1.8 mm. The interfacial polarization mechanism for enhanced MA performance was demonstrated by electron holography and density functional theory calculations. Magnetic holography and micromagnetic simulations also revealed magnetic confinement and coupling mechanism. This work provides a new approach for designing electromagnetic absorbers with optimized impedance matching and loss capability.

Co3O4 nanoparticles-embedded nitrogen-doped porous carbon spheres for high-energy hybrid supercapacitor electrodes

This work synthesizes cobalt oxide (Co3O4)-embedded nitrogen-doped porous carbon spheres (Co3O4@NPCS) with inherent hierarchical structures through hydrothermal and pyrolysis processes. The synthesized material shows porous spherical carbon with nitrogen functionalities and contains Co3O4 nanoparticles on the surface of the carbon framework. The hybrid supercapacitor (HSC) is fabricated by Co3O4@NPCS and NPCS as anode and cathode, respectively, using aqueous KOH as electrolyte. The HSC displays exceptional electrochemical performance over the wide voltage window of 1.5 V with a large capacitance of 464 F g−1 at 1 A g−1, a high energy of 98.5 Wh kg−1, and power of 1500 W kg−1. Long charge-discharge cyclic stability demonstrates 87.2 % capacitance retention of the HSC over 10,000 cycles with almost 100 % coulombic efficiency. Additionally, first principles investigations show that the improved hybrid supercapacitors performance is as a consequence of the increased conductivity and the charge transfer. The proposed electrode and hybrid design show a potential for future high-energy storage.

Versatile polydopamine-mediated growth of N and C co-doped hollow porous TiO2 spheres with oxygen vacancies for visible-light-driven oxidation of acetaldehyde

Developing visible-light-responsive TiO2-based photocatalysts provides a promising avenue for addressing VOCs pollution. Herein, polydopamine (PDA) template pyrolysis waste was in-situ up-cycled for simultaneous growth of N and C co-doped hollow porous TiO2 microreactors (H-NT-0.2) in air. The resulting H-NT-0.2 with a highly intact hollow structure, thin spherical shell (∼ 13 nm) and high porosity possesses the highest N and C co-doping ratio and largest oxygen vacancies (OVs) amount, leading to the highest concentration of reactive oxygen species (ROS) among all H-NT-x. A crucial role of OVs in enhancing H2O adsorption for the generation of hydroxyl radicals (⋅OH) has been revealed by DFT calculations. As a result, H-NT-0.2 shows the highest photocatalytic oxidation (PCO) efficiency of flowing acetaldehyde gas (90%) under visible light irradiation, which exceeds 3.5 times of commercial TiO2 (P25)), and outperforms most of the reported photocatalysts. The growth mechanism, as well as the photocatalytic reaction pathways, were analyzed based on TG-MS and in-situ DRIFTS results, respectively. This work provides an economical, green and feasible strategy to develop advanced visible-light-responsive photocatalysts for aldehydes VOCs abatement in practical applications.

An energetic MOF-assistant confined expansion strategy to fabricate Fe-doped porous carbon beads for advanced oxidation processes: Interfacial reaction mechanism and biological toxicity

Porous carbon material catalysts derived from MOFs-based precursors are gradually being used extensively in advanced oxidation possesses. However, some of the existing problems such as hard to recovery and easy to secondary pollution still need to be solved. Here, a series of Fe-doped energetic metal–organic framework (EMOF)-derived porous carbon spheres (EMFexS) were obtained by the phase inversion route. EMOFs puffed up during pyrolysis at high temperatures to create large-sized hierarchically porous structure. The large specific surface area (483.4 m2/g) and high nitrogen content, and hierarchically porous structure endow EMFe0.2S with excellent catalytic performance to remove tetracycline removal efficiency. By activating peroxymonosulfate (PMS), it was found that the rate constant (k) in EMFe0.2S/PMS system was 0.058 min−1, which was 1.75, 1.56 and 1.52 times than that of EMFe0S/PMS system, EMFe0.1S/PMS system and EMFe0.25S/PMS system, respectively. Experiments and material characterization point that the existence of nitrogen and iron in the catalyst were the potential active sites. The continuous flow catalytic reaction and biological toxicity experiments were employed to evaluate practical application value. This study provides new insights into the preparation of microspheres for water treatment with the help of EMOF-assisted confined expansion strategy.

In situ constructing Co/Co-Ox/Co-Nx diverse active sites on hollow porous carbon spheres derived from Co-MOF for efficient bifunctional electrocatalysis in rechargeable Zn-air

Earth-rich, durable, and efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is vitally important for the wide application of zinc-air batteries in the future. However, due to the single active site, traditional commercial benchmark catalysts typically exhibit selective activity in only one of the two reactions (ORR or OER), making it difficult to meet the dual functional catalytic requirements. Developing efficient oxygen electrocatalysts that achieve diverse active sites on a single catalyst and understanding their internal synergistic reaction activity remain a challenge. Herein, spherical hollow porous carbon matrix composites (s-Co/CoNC) with the coexistence of diverse intrinsic active sites including Co-Nx and Co-Ox species and metal Co nanoparticles were prepared by pyrolysis with oxygen-enriched Co-MOFs as precursor in the presence of melamine. Owing to the combined advantages of the catalyst including the great specific surface area, good conductivity, abundant diverse intrinsic active sites towards ORR and OER, and the electronic interaction among active sites and the optimized the adsorption/desorption process of oxygen species at the catalyst surface, s-Co/CoNC exhibits desirable electrocatalytic activity for both ORR and OER with an ORR half-wave potential of 0.81 V, an OER potential of 1.53 V(vs. RHE at 10 mA cm−2), providing a small reversible potential difference of 0.72 V, superior to the commercial noble-metal catalysts and the most reported cobalt based ORR/OER catalysts. The assembled s-Co/CoC-based rechargeable Zn-air batteries possess high peak power density of 101.7 mW cm−2. This work provides a significant strategy for constructing high-performance dual functional catalysts for secondary Zn-air batteries.

Photocuring-assisted emulsion of ceramic suspensions containing phase-separable camphene/photopolymer vehicle for porous ceramic spheres

We herein describe photocuring-assisted emulsion of a ceramic suspension prepared using a thermo-regulated phase-separable camphene/photopolymer vehicle for synthesis of porous hydroxyapatite (HA) spheres with unique porous structures. HA suspensions with different camphene contents (60 vol %, 70 vol %, and 80 vol %) were prepared by dispersing HA particles in various camphene/hexanediol diacrylate (HDDA) solutions at room temperature and then emulsified in an aqueous polyvinyl alcohol (PVA) solution via magnetic stirring. Emulsions were frozen at −20 °C for phase separation of camphene/HDDA solutions and then photocured for polymerization of HDDA enclosing HA particles. Synthesized spheres were freeze-dried to remove the camphene-rich crystals. All spheres sintered at 1250 °C for 3 h had well-defined spherical shape with three-dimensionally interconnected pores. The porosity of individual HA spheres increased from ∼ 56.5 vol % to ∼ 78.7 vol % with an increase in camphene content from 60 vol % to 80 vol %.

Rapid PFOS mineralization with peroxydisulfate activation process mediated by N modified Fe-based catalyst

As the cheap and efficient catalysts, the iron-based catalysts have been considered as one of the most promising catalysts for peroxydisulfate (PDS) activation and the development of high-performance iron-based catalysts are attracting growing attentions. In this work, a magnetic Fe-based catalysts (Fe/NC-1000) was obtained by using Fe modified ZIF-8 as the precursor and used to activate the PDS for the degradation of perfluorooctane sulphonate (PFOS). Morphology and structure analysis showed that the resulted Fe/NC-1000 catalyst was displayed porous spheres (40–60 nm) and mainly composed of Fe0, FeNx and carbon. When Fe/NC-1000 was employed to activate the PDS (0.1 g/L of catalyst dosage, 0.5 g/L of PDS dosage and at initial pH of 4.6), the Fe/NC-1000/PDS system exhibited excellent efficiency (97.9 ± 0.1) % for PFOS (10 mg/L) degradation within 30 min. The quenching tests and EPR results revealed that the Fe/NC-1000/PDS system degraded PFOS primarily through singlet oxygen (1O2) evolution and electron-transfer process. Besides, based on the degradation byproducts determined by LC-MS-MS, the PFOS first occurred de-sulfonation to form PFOA, and then the resulted PFOA underwent stepwise defluorination in the Fe/NC-1000/PDS system. Density Functional Theory (DFT) calculations and electrochemistry tests strongly confirmed that Fe/NC-1000 exhibited high electron transfer efficiency, resulting in promoted performance on activating PDS. Importantly, the results of Ecological Structure-Activity Relationship (ECOSAR) analysis showed that the intermediates were lowly toxic during the PFOS degradation, manifesting a green process for PFOS removal. This study would provide more understandings for the persulfate activation process mediated by Fe-based catalysts for Perfluorinated alkyl substances (PFAS) elimination.

Spherical porous structures for axial compression

Porous structures have attracted much attention because of the advantages of lightweight and strong energy absorption efficiency. This work proposes a spherical porous structure (SPS) and a square porous structure (SQPS), and the SPS sample is manufactured by selective laser sintering (SLS) technique with the material nylon 11. Their axial compression results of experiment and simulation show that the compressive strength of hollow cylinders is greater than that of porous spheres, and porous spheres are always crushed during compression. SPS exhibits the rapid collapse characteristics of porous spheres layer by layer, and it shows four sharp valley forces and significant negative stiffness characteristic. In addition, the specific energy absorption (SEA) value of SPS is higher than that of SQPS 30.84%. The compression capacity of porous spheres is stronger than that of porous cubes. This study furtherly discuss the mechanical behavior of SPS with different structural parameters. The negative stiffness characteristic, energy absorption efficiency and deformation mode of SPS depends on the strength combination of porous spheres and hollow cylinders, and smaller overall cell size, more cell layers, and thicker cells contribute to improving the anti-compression properties of SPS. The SEA values of SPS- T1.6 and SPS- F7 are 12.52% and 12.16% higher than that of SPS. In summary, SPS shows novel mechanical properties, providing a reference for the design of new energy absorbers.

One-pot Mild Hydrothermal Synthesis of the Nanosheets Constructed Cobalt Silicate Hydroxide Hierarchical Porous Hollow Submicron Spheres as Efficient Adsorbents for Organic Dyes Removal

One-pot Mild Hydrothermal Synthesis of the Nanosheets Constructed Cobalt Silicate Hydroxide Hierarchical Porous Hollow Submicron Spheres as Efficient Adsorbents for Organic Dyes Removal

Porous magnetic carbon spheres with adjustable magnetic-composition and synergistic effect for lightweight microwave absorption

The chemical composition of reduced magnetic particles strongly correlates with the reduction potential of their metal species. However, this phenomenon rarely has been investigated in magnetic-dielectric absorbers. In this manuscript, a formaldehyde-assisted metal-ligand crosslinking strategy is employed to incorporate different metal species (Fe3+, Co2+, Co2+-Ni2+) into the colloidal frameworks by the chelating coordination. Because of their different reduction potentials, porous magnetic carbon spheres (PMCSs) with adjustable magnetic-composition and micro-mesoporous characteristics are constructed via the subsequent annealing process. Compared with self-assembly polyphenol derived porous carbon spheres (PCSs), these PMCSs, including Fe3O4-PMCSs, Co-PMCSs and CoNi-PMCSs, exhibit promoted impedance matching and superior microwave absorption attenuation owing to the additional magnetic resonance and synergistic effect. As results, the optimal reflection loss and corresponding bandwidth are −48.6 dB and 7.8 GHz, −45 dB and 8.6 GHz, −53.2 dB and 5.1 GHz for Fe3O4-PMCSs, Co-PMCSs and CoNi-PMCSs with only 15 wt% filler loading, both are higher than PCSs (−39.3 dB and 4.8 GHz). This study inspires us a novel inspiration in constructing of adjustable magnetic-composition and the fabricated PMCSs can be used as lightweight microwave absorbers in the application of electromagnetic protection.

Soft-template hydrothermal synthesis of N and B co-doped walnut-shaped porous carbon spheres with hydrophilic surfaces for supercapacitors

Biomass-derived carbon electrodes have attracted attention for alternative energy storage devices. However, it remains a challenge to obtain a hydrophilic surface while preserving the structure, stability, and reactivity. N and B co-doped walnut-shaped porous carbon spheres with hydrophilic surfaces were prepared by hydrothermal carbonization of glucosamine, boric acid, and triblock copolymers, followed by chemical vapor phase oxidation. Walnut-shaped structure can shorten the electron and ion transport pathways and improve diffusion efficiency. N and B atoms doped in the forms of pyridine N (N-6), pyrrole N (N-5), graphite N (N-Q), N oxide (N-Ox), or N-B, as well as CB3, CB2O, CBO2, or B-N can improve the stability, conductivity, and reactivity. Hydrophilic surface can promote the wetting of the electrolyte on carbon electrodes. Therefore, N and B co-doped walnut-shaped porous carbon spheres exhibit useful electrochemical performance. The specific capacitance reaches 281F·g−1 at a current density of 0.2 A·g−1, and the rate performance reaches 75% at 5 A·g−1. The assembled symmetrical supercapacitor shows a high specific capacitance of 189 F·g−1 at 0.1 A·g−1 and an energy density of 6.56 W·h·kg−1. Furthermore, it exhibits a high cycle stability after 5000 cycles at 2 A·g−1, maintaining 95% of initial specific capacitance.