Porous Flower-like Structure Research Articles

Effective As(V) removal using in situ grown Ti-based MOFs on ZnAl-LDHs

Herein, we synthesize the ZnAl-LDHs/NH2-MIL-125 composite via in situ growth of Ti-based metal–organic framework (MOFs) using layered double hydroxide (LDHs) as a carrier. The composite exhibits excellent performance for As(V) removal, achieving an adsorption capacity of 1634.0 mg/g in wastewater with an As(V) concentration of 1500 mg/L at pH of 10. The porous flower-like structure of the composite inherits the benefits of both the spatial structure of MOFs and the arsenic-affinity of LDHs. This results in an abundant active surface containing –OH, –NH2, M–O–M, and –COO– species, collectively contributing to As(V) adsorption. The adsorption progress governing As(V) removal follows the Langmuir isotherm and pseudo-second-order (PSO) kinetic models, revealing a monolayer and chemisorption mechanism. This study showcases the feasibility of the in situ growth of a MOF on LDHs to synthesize high-capacity adsorbents, offering a potential solution for As(V) removal from wastewater.

Enhanced thermal storage and photo-thermal conversion composite phase change materials based on MOF-derived carbon for efficient solar energy utilization

Composite phase change materials (PCMs) with high thermal conductivity and photo-thermal conversion performance can be employed for the efficient conversion and utilization of solar energy. In this work, a Ni-doped carbon material derived from a Ni metal-organic framework (Ni-BTC) is prepared and used as the supporting material to encapsulate polyethylene glycol (PEG). The Ni-BTC derived carbon (NBC) obtained retained the intrinsic porous flower-like structure which facilitates the encapsulation of PEG. The doping of Ni metal particles enhances both the thermal conductivity and photo-thermal conversion performance of the composite PCM. Additionally, the thermal conductivity of the composite PCM is further enhanced by the addition of a graphene/Ag composite, resulting in a thermal conductivity that is 3.15 times higher than that of pure PEG. The latent heat of the resulting composite PCM is 125.4 J/g, the photo-thermal conversion efficiency is 91.81 %. Moreover, the composite PCM exhibits excellent thermal stability and reliability, indicating its potential for wide-ranging applications in solar energy storage.

Enhanced Activity and Stability of Heteroatom-Doped Carbon/Bimetal Oxide for Efficient Water-Splitting Reaction.

The research community is actively exploring ways to create cost-efficient and high-performing electrocatalysts for the oxygen evolution reaction. In this investigation, an innovative technique was employed to produce heteroatom-doped carbon containing NiCo oxides, i.e., HC/NiCo oxide@800, in the form of a three-dimensional hierarchical flower. This method involved the reduction of a bimetallic (Ni, Co) metal-organic framework, followed by carefully controlled oxidative calcination. The resulting porous flower-like structure possess numerous advantages, such as expansive specific surface areas, excellent conductivity, and multiple electrocatalytic active sites for both hydrogen and oxygen evolution reactions. Moreover, the presence of oxygen vacancies within HC/NiCo oxide@800 significantly enhances the conductivity of the NiCo substance, thus expediting the kinetics of both the processes. These benefits work together synergistically to enhance the electrocatalytic performance of HC/NiCo oxide@800. Empirical findings reveal that HC/NiCo oxide@800 electrocatalysts demonstrate exceptional catalytic activity, minimal overpotential, and remarkable stability when deployed for both hydrogen evolution and oxygen evolution reactions in alkaline environments. This investigation introduces a fresh avenue for creating porous composite electrocatalysts by transforming metal-organic frameworks with controllable structures. This approach holds promise for advancing electrochemical energy conversion devices by facilitating the development of efficient and customizable electrocatalytic materials.

Construction of various morphological ZnO-NiO S-scheme nanocomposites for photocatalytic dye degradation

The textile industry has a global environmental impact because of its discharge or dumping of wastewater into rivers, which has a significant impact on water resource quality. The removal of pollutant dyes from water using simple and efficient procedures is gaining interest worldwide. Hence, herein, a simple one-pot solvothermal technique is used to create various types of ZnO/NiO hierarchical nanostructures for photocatalytic dye degradation. Alcoholic solvents, such as ethanol, methanol, and propanol, were utilized for the formation of these nanostructures. The production of porous, marigold-like structures was observed through a morphological investigation. Appropriate characterization techniques were used to investigate the absorptivity, chemical composition, elemental state, crystallinity, and recombination rate. The porous flower-like structure with unique exciton acquisition demonstrated 82 % azo dye degradation, which was ∼ 3 and 2.5 times greater than those using pure ZnO and NiO structures, respectively. Reduced charge carrier recombination, rapid migration of produced electrons to the catalyst surface, and a mounted heterojunction across the interface contributed to this outstanding performance. Furthermore, the composite demonstrated remarkable reusability, retaining a dye degradation efficiency of 74 % after ten cycles. The nanostructure and remarkable dye-degrading capability of the synthesized composites demonstrate that they are suitable for photocatalysis applications.

Achieving electromagnetic wave absorption capabilities by fabrication of flower-like structure NiCo2O4 derived from low-temperature co-precipitation

In this work, The NiCo2O4 with 3D hierarchical multilayer flower-like structure was prepared by the low-temperature (55 °C) co-precipitation method combined with the calcination process, avoiding the traditional high-temperature hydrothermal synthesis method. The prepared flower-like NiCo2O4 with a large specific surface area was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and automatic surface area and porosity analyzer (BET) and vector network analyzer (VNA). A novel evaluation approach was proposed to evaluate the electromagnetic wave (EMW) absorbing properties of various samples (different calcination temperatures), which was to defined the ΔS as the area enclosed by the curve when the reflection loss (RL) value was less than −10. In order to take the material thickness into account, and then the effective reflection loss (RLE) value was defined ΔS/d to measure the electromagnetic wave (EMW) loss capability of the different samples. The results showed that NiCo2O4 exhibited excellent EMW absorption effect when the calcination temperature was 400 °C, and the maximum RL value reached −43.17 dB at 14.32 GHz with the thickness of 1.5 mm and the effective absorption bandwidth (fe) was 4.48 GHz (12.08 GHz–16.56 GHz). The excellent EMW absorption property was mainly due to NiCo2O4 with particular porous flower-like structure, which could achieve impedance matching to loss EMW by dielectric loss and magnetic loss.

Preparation of CNFs/RGO/CuS Composite Materials with Porous Structure and Excellent Microwave Absorption Performance

In this study, green cellulose nanofibers-based composites were successfully prepared for efficient wide-band electromagnetic absorber to realize functional and high-value diversified utilization of cellulose nanofibers. Specifically, by the introduction of reduced graphene oxide (RGO) and flower-like copper sulfide (CuS) into CNFs used as raw material, CNFs/RGO/CuS porous composite microwave absorber were obtained. The CNFs/RGO/CuS porous composite exhibited excellent microwave absorption performance due to its unique three-dimensional porous flower-like structure and heterogeneous interface, which provided excellent impedance matching and attenuation capabilities. The fabricated CNFs/RGO/CuS composite exhibited a minimum reflection loss (RLmin) of [Formula: see text]49.71[Formula: see text]dB at 11.52 GHz and a maximum absorption bandwidth of 5.30 GHz (from 10.40 GHz to 15.70 GHz) at only 2.50[Formula: see text]mm. In addition, the scanning electron microscope (SEM) results showed that the CNFs/RGO/CuS composite had a porous microstructure. And the Brunauer–Emmett–Teller (BET) specific surface area of the CNFs/RGO/CuS composite was 326.46[Formula: see text]m2/g. Potential absorption mechanisms were proposed considering the interfacial polarization, impedance matching, and dielectric losses caused by the synergistic effects among CNFs, RGO, and CuS. This work proposed a new strategy to biomass-based functional materials, and used the natural polymer CNFs, compounded with reduced graphene oxide and copper sulfide, to achieve efficient microwave absorbing materials.

Modulation electronic structure of NiS nanoarray induced by Fe, V doping for high efficiency water and urea electrolysis

Exploring high-efficient and stable low-cost electrocatalysts is of significant importance for boosting the efficiency of water splitting and purifying urea-enriched wastewater. Herein, bimetallic doping strategy was adopted to obtain jasminum nudiflorum-like Fe, V doped NiS arrays (Fe, V-NiS/NF) via typical hydrothermal process and subsequent anion exchange reaction. The as-obtained Fe, V-NiS/NF array displays high catalytic activity and stability toward oxygen evolution reaction (OER) and urea oxidation reaction (UOR) in alkaline media, with reduced overpotentials of 273 and 214 mV to deliver the current density of 50 mA cm−2 for OER and UOR, respectively. More notably, when employing Fe, V-NiS/NF as symmetric electrolytic cell for urea electrolysis, a low cell voltage of 1.45 V is needed at 10 mA cm−2, which is about 110 mV lower than the conventional water electrolysis. Meanwhile, the catalyst also displays superior stability for over 72 h. Such outstanding performance is attributed to the following points: (i) 3D porous flower-like structure facilitates the mass transfer and abundant exposure of active sites; (ii) in situ growth of catalysts on conductive substrate and the effective interface engineering of different composition shorten the charge transport pathways and expedite electron transfer. Density functional theory calculations demonstrate that the Fe and V dopants regulate the electronic environment of Ni sites and optimize the adsorption free energy of urea. This work provides a universal pathway to design high-efficient and non-noble electrocatalysts for H2 production in an energy-saving way via urea electrolysis.

Defect-Rich, Highly Porous PtAg Nanoflowers with Superior Anti-Poisoning Ability for Efficient Methanol Oxidation Reaction.

The design of efficient and sustainable Pt-based catalysts is the key to the development of direct methanol fuel cells. However, most Pt-based catalysts still exhibit disadvantages including unsatisfied catalytic activity and serious CO poisoning in the methanol oxidation reaction (MOR). Herein, highly porous PtAg nanoflowers (NFs) with rich defects are synthesized by using liquid reduction combining chemical etching. It is demonstrated that the proportion of precursors determines the inhomogeneity of alloy elements, and the strong corrosiveness of nitric acid to silver leads to the eventual porous flower-like structure. Impressively, the optimal etched Pt1 Ag2 NFs have the mixed defects of surface steps, dislocations, and bulk holes, and their mass activity (1136mA mgPt-1 ) is 2.6 times higher than that of commercial Pt/C catalysts, while the ratio of forward and backward peak current density (If /Ib ) can reach 3.2, exhibiting an excellent anti-poisoning ability. Density functional theory calculations further verify their high anti-poison properties from both an adsorption and an oxidation perspective of CO intermediate. The introduction of Ag makes it easier for CO to be oxidized and removed. This study provides a facile approach to prepare rich defects and porous alloy with excellent MOR performance and superior anti-poisoning ability.

Cobalt/graphene oxide nanocomposites: Electro-synthesis, structural, magnetic, and electrical properties

In this research, different samples of cobalt/graphene oxide nanocomposites were successfully synthesized electrochemically by applying different voltages. Their structure, magnetization and electrical properties were studied using X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), atomic force microscope (AFM), fourier transformation infrared (FT-IR), vibrating sample magnetometer (VSM), two point probe electrical conductivity meter, galvanostat/potentiostat, and universal testing machine. The results of structural characterization confirmed the formation of cobalt/graphene oxide nanocomposites. The FESEM images showed the porous flower-like structure of particles deposited on the graphene oxide sheets. The AFM images clearly showed the surface roughness and the dispersion of nanoparticles on graphene oxide sheets. Room-temperature magnetization values range from 18 emu g−1 to 167 emu g−1, depending on the applied voltage. In order to study the electrical properties of the nanocomposites, the volumetric resistivity and volumetric conductivity under different pressures and the current-voltage characteristic curves were measured. Based on the results, the nanocomposites synthesized by applying 8 V and 23 V show ohmic behavior and have the highest volumetric conductivity. The volumetric conductivity increases with increasing the pressure. The nanocomposite prepared by applying 23 V presents good structural, magnetic, and electrical properties.

Physicochemical properties and microwave absorption performance of Co3O4 and banana peel-derived porous activated carbon composite at X-band frequency

Agricultural waste-derived absorbers have drawn extensive attention in electromagnetic wave absorption owing to their unique advantages such as good carbon content and porosity. In this study, porous activated carbon (PAC) was derived from banana peel via chemical activation and carbonization at different temperatures. Then, Co3O4@PAC composites were prepared using the facile hydrothermal method. The thermal stability, phase crystallinity, chemical composition, surface morphology, and porosity of the samples were studied using TGA, XRD, FTIR, XPS, FESEM, and SAP characterization techniques, respectively. Co3O4@PAC700 composite with a cornales flower-like morphology achieved an optimum reflection loss (RL) of −44.50 dB at 2.0 mm thickness. Likewise, Co3O4@PAC600 showed an optimum RL value of −51.50 dB at 11.39 GHz with a matching thickness of 2.5 mm. The magnetic loss, interfacial polarization, porous flower-like structure, and conduction loss contributes adequately towards the superior absorption performance of Co3O4@PAC composites at X-band frequency. The unique flower-like morphology of the composites with good porosity would favour EM wave scattering and multiple reflections of EM wave, thereby resulting in high attenuation of the EM wave. The flower-like morphology prolongs the electromagnetic wave propagation path which would favour gradual attenuation of the electromagnetic wave. This work suggests that the Co3O4@PAC composites can be considered as a promising absorber for EM absorption application. This study provides a new path to designing novel magnetic and dielectric composite for effective microwave absorption.

Self-assembled 3D flower-like Ni(OH)2 nanostructures and their Ni–Zn cell applications

A high-performance nickel cathode material HPMo/Ni(OH)2 for the Ni–Zn cell is developed by using phosphomolybdic acid (HPMo) as a structure-directing agent. Its three-dimensional porous flower-like structure makes the active material possess the advantages of high specific surface areas, rich active sites, easy electrolyte accesses, and fast electron transfer. Combined with these advantages, the Ni–Zn cell of HPMo/Ni(OH)2 as the cathode, ZnO as the anode, exhibits a high specific capacity of 277.5 mAh g− 1 (cut off 1.5 V), and even up to 346.9 mAh g− 1 during deep discharge (cut off 0.5 V) at 2.5 A g− 1. When the ZnO/graphene as the anode, the cycle life of HPMo/Ni(OH)2 can extend to 10,000 at 5 A g− 1. Besides, this is the first time that the three-dimensional nickel hydroxide is produced in large quantities with simple preparation process using phosphomolybdic acid as a structure directing agent. This also provides a new synthesis strategy for the self-assembly of 3D nanomaterials, and presents new prospects for the development of more advanced energy storage materials.

Mn/Co oxide on Ni foam as a bifunctional catalyst for Li–air cells

Binary Mn/Co oxide sheets with spherical flower-like hierarchical structure are grown directly on the surface of a Ni foam skeleton as a cathode for Li–O2 batteries using a hydrothermal method. This integrated cathode architecture eliminates the negative effects of a conductive carbon additive and binder on the electrochemical performance of Li–O2 batteries and minimizes the processing steps in fabrication of cathodes for Li–O2 batteries. The porous Ni foam acts as a scaffold and current collector, and the highly hierarchical porous flower-like structure of the binary Mn/Co oxide sheet acts as a highly active catalyst. Together, they facilitate effective diffusion of oxygen gas as well as rapid ion and electron conduction during electrochemical reactions. When assembled in Li–O2 cells, the prepared catalyst exhibits excellent catalytic activities, including the oxygen reduction and oxygen evolution reactions. In particular, the Li–O2 cell using the cathode delivers an extremely high specific discharge capacity of 9690 mAh g-1 under a applied specific current of 200 mA g-1 and operate successfully in a long lifespan of 66 cycles even under a high specific current of 600 mA g-1 and a limited discharge-charge capacity mode of 1000 mAh g-1. The simultaneous effect of the fast electron transport kinetics provided by the free-standing structure and the high catalytic activity of the binary Mn/Co oxide show promise for use in air electrodes for Li–O2 batteries.

SnS2-gC3N4/rGO Composite Paper as an Electrode for High-Performance Flexible Symmetric Supercapacitors

The flexible, free-standing, durable SnS2-gC3N4/rGO paper material was prepared by vacuum filtration of the composite dispersion containing GO and the SnS2-gC3N4 composite structure which is synthesized by a simple hydrothermal method. The as-prepared SnS2-gC3N4/GO composite paper was converted to SnS2-gC3N4/rGO paper material by applying a chemical reduction process. SnS2-gC3N4/rGO paper material was characterized by using FESEM, XRD, Raman, XPS, and EIS spectroscopy techniques. The SnS2-gC3N4 composite, a porous flower-like structure, uniformly intercalated between the graphene nanosheets exhibited excellent mechanical stability, greatly improved active surface areas, and enhanced surface porosity, in comparison with the pristine rGO paper. SnS2-gC3N4/rGO composite paper material show a highest specific capacitance of 532 F g-1 at 1 A g-1 and good cycling stability with capacitance retention of 60 % at 4 A g-1 after 5000 cycles. Moreover, SnS2-gC3N4/rGO composite paper demonstrate an excellent supercapacitor performance compared to the gC3N4/rGO paper and pristine rGO paper. The flexible symmetric supercapacitor based on SnS2-gC3N4/rGO composite electrode exhibits remarkable mechanical flexibility, high capacitive performance (403 F g-1 at 1 A g-1) and high cycle stability (63.8% at 4 A g-1 after 1500 cycles). As a result, SnS2-gC3N4/rGO composite paper material is expected to be a promising material for high-performance energy storage applications.

Impacts of morphology and N-doped carbon encapsulation on electrochemical properties of NiSe for lithium storage

Metal selenides are attractive anode materials for Li-ion batteries. However, poor structural stability and poor cycle performance limit the application of metal selenides. In this work, a solvent-directed self-assembly method is applied to prepare N-doped carbon-encapsulated nickel selenide (i.e., NiSe@N-doped carbon). Through simply adjusting the ratio of mixed solvent (H2O and ethanol) and coordination agent, NiSe-based anode with diverse morphologies including nanosheet-assembled multi-leaves NiSe, hierarchical porous flower NiSe@N-doped carbon, hexagonal plate NiSe@N-doped carbon, and multishell hollow sphere NiSe can be obtained after selenization. These anode materials possess distinct electrochemical performance owing to their different electrochemical kinetics, structural stability, and solid electrolyte interphase (SEI) growth. By introducing N-doped carbon encapsulation and constructing the well-defined hierarchical porous flower-like structure, the electrochemical performance is greatly enhanced, and moreover, the contents of SEI components (like NiF2, LixPOyFz, LiF, Li2CO3, etc.) can also be effectively reduced.

Facile one step solvothermal synthesis and high visible light photocatalytic property of flower-like Bi2O3/BiOBr microspheres

Abstract We used facile one step solvothermal method to fabricate Bi2O3/BiOBr microspheres with porous flower-like structure which has good photocatalytic degradation ability to Rhodamine B. Meanwhile, the active species during photocatalytic reaction were explored. The results showed that the catalytic activity of Bi2O3/BiOBr was higher than that of BiOBr. After 140 min’ irradiation with 7 W LED lamp, the degradation efficiency of the Bi2O3/BiOBr photocatalyst reached 91.4%. The larger specific surface area and higher visible light utilization both improved the photocatalytic activity. O2− and h+ played a major role in the reaction process.

Catalytic Performance of Novel Hierarchical Porous Flower-Like NiCo2O4 Supported Pd in Lean Methane Oxidation

In this work, NiCo2O4 with a hierarchical porous flower-like structure was fabricated and used as catalyst support for Pd nanoparticles. The NiCo2O4 was composed of porous nanoplates without overlapping, and the Pd nanoparticles were uniformly distributed on these nanoplates. Pd–NiCo2O4 with the Pd loading of 2.0 wt% showed extremely high activity and stability, methane (1.0% CH4/Air) can be totally oxidized at 330 °C and the T90 is 309 °C, which is much lower than that of pure NiCo2O4 (T90 = 405 °C). At wet condition with the presence of 10 vol% water vapor, the catalytic activity was still acceptable with the T90 of 366 °C, and no activity decrease or permanent damage for the catalyst was observed after 35 h reaction, showing high stability. A series of techniques including TEM, SEM, XRD, H2-TPR, BET and especially quasi in situ XPS combined with in situ MS were used to characterize the catalysts and investigate the catalysis mechanism. Two pathways of CHO evolution were proved by the quasi in situ XPS and in situ MS results: OCHO intermediate dehydrogenation pathway at lower temperature and CO oxidation pathway of CHO at higher temperature.

In situ construction of porous NiCo2O4/Ni foam electrodes for high-performance energy storage applications

A novel three-dimensional (3D) porous flower-like NiCo2O4 electrode is reported. The electrode is constructed by homogeneous chemical co-precipitation involving the in situ growth of ternary nickel cobaltite nanosheets on a Ni foam, and a high temperature heat treatment. Field emission electron microscopy (FESEM) demonstrate that the porous flower-like structure is made up of uniform thin nanosheets with thickness of about 10 nm. Electrochemical studies reveal that the porous flower-like electrode exhibits excellent supercapacitor behavior with a high initial specific capacitance of 1046 F g−1 (at 1 A g−1) and stable cycling performance.

Porous flower-like NiO@graphene composites with superior microwave absorption properties

Novel porous flower-like NiO@graphene composites with superior microwave absorption properties dues to good impedance matching, the special porous flower-like structure, polarization effects and conductivity loss.

Morphology-controlled synthesis of Co3O4 porous nanostructures for the application as lithium-ion battery electrode

Porous Co3O4 nanostructures with morphologies including hierarchical nanoflowers and hyperbranched nano bundles have been successfully synthesized by a controlled hydrothermal method and subsequent calcinations at higher temperature. Microscopic characterizations have been performed to confirm that mesoporous Co3O4 nanostructures are built-up by numerous nanoparticles with random attachment. The specific surface area and pore size of the nanoflowers have been found ∼51.2m2g−1 and 12.6nm respectively. The nanoflowers as an anode materials for lithium-ion batteries (LIBs) demonstrate the higher initial discharge capacity of 1849mAhg−1 with a Columbic efficiency 64.7% at a rate of 50mAhg−1 between 0.01 and 3.0V. In addition, a significantly enhanced reversible capacity ∼980mAhg−1 is retained after 30 cycles. More interestingly, excellent high rate capabilities (∼ 960mAhg−1 at 250mAg−1 and ∼875mAhg−1 at 500mAg−1) are observed for porous flower-like structure. The improved electrochemical performance is attributed to the large specific surface area and porous nature of the flower-like Co3O4 structure which is more convenient and accessible for electrolyte diffusion and intercalation of Li+ ions into the active phases. Therefore, this structure can be considered to be an attractive candidate as an anode material for LIBs.

Morphology and Optical Properties of Nickel Oxide Nanostructure from Aqueous Solution

In this paper, porous flower-like nickel oxide (NiO) on glass substrates were prepared by an aqueous chemical growth based technique. The morphology and optical observed were found to be influence by the reaction time. Field Emission Scanning Electron Microscopy (FESEM) revealed a porous flower-like structure growth on the substrates investigated. The optical band gap for NiO thin film calculated from transmission spectra has increased from 3.72 eV to 3.91 eV with the increasing of reaction time. This result shows that the growth time have some influence on morphology and optical of NiO films.