Three-dimensional Hierarchical Architectures Research Articles

Engineering hierarchical heterostructure material based on multiwalled carbon nanotubes/SnO2 nanorod-flowers for high-efficient ammonia detection

The rational manufacturing of multi-component materials with rich heterostructure is emerging as a possible strategy to develop improved carbon nanotube-based gas sensors. Herein, hierarchical heterostructure of multiwalled carbon nanotubes/SnO2 nanorod-flowers (HMCNS) was synthesized by a facile water-bathing combined hydrothermal approach for highly sensitive ammonia detection. Exploration in the microstructure reveals that hierarchical flowers-like SnO2 consisted of nanorods demonstrates a hollow geometry for wrapping multiwalled carbon nanotubes, featuring a unique three-dimensional (3D) hierarchical architecture. Gas sensor based on SnO2@4.5%CNTs hierarchical heterostructure exhibits highly enhanced ammonia-sensing performances, including ultra-high response of 1650 toward 20 ppm ammonia, good selectivity, 250 ppb level detection, and superior long-term stability. The improvement in ammonia sensing capability could be attributed to the peculiar hierarchical architecture and the creation of Mott-Schottky heterostructure which has been strongly validated by electrochemical research. This work will provide a concise and effective avenue to construct hierarchical composite with Mott-Schottky heterostructure for high-performance ammonia gas sensor.

Electrodeposited three-dimensional hierarchical architecture of MgO anchored with Ag nanoparticles for high-performance symmetric supercapacitors

A blossom-like, three-dimensional (3D) hierarchical architecture of MgO anchored with silver nanoparticles (Ag NPs) is developed using a simple galvanostatic electrodeposition method. This study shows how electrochemical performance is improved by the incorporation of Ag NPs within a 3D framework. The 3D blossom-like scaffold comprises thin 2D petals, whose porous lace-like patterns provide a large surface area and many channels for the rapid diffusion of electrolyte ions. The anchored Ag NPs increase the electrical conductivity of the MgO structure and enhance redox reactions. An optimum Ag loading of 10 vol% on MgO (MgO@Ag-10) affords a 100-fold enhancement in specific capacitance over that of MgO. This hybrid MgO@Ag-10 electrode on a stainless-steel substrate yields a specific capacitance of 388.6 F.g−1 (134.85 mF.cm−2) at a current density (CD) of 1 mA.cm−2, whereas pure MgO delivers only 3.72 F.g−1 (3.1 mF.cm−2) at the same CD in a three-electrode system. The MgO@Ag-10 electrode also exhibits 88.6 % capacitance retention over 5000 charge–discharge cycles. A symmetric supercapacitor device comprising two MgO@Ag-10 electrodes exhibits a specific capacitance of 42 F.g−1, an energy density of 23.33 Wh.kg−1, and a power density of 8000 W.kg−1 at 4 mA.cm−2 in aqueous KOH.

2D MOF based-heterostructure with hierarchical architecture as antibacterial wound dressing

Bacterial infections pose a huge threat to human health due to the inevitable emergency of drug resistance. Metal-organic frameworks (MOFs) consisting of metal ions and organic linkers, as emerging efficient antibacterial material, have the merits of structural flexibility and adjustable physicochemical property. With assistance of photosensitive agents as organic linkers, MOFs have great potential in antibacterial application through photocatalytic therapy by the generation of reactive oxygen species (ROS). However, the limited light use efficiency and short lifespan of ROS are two obstacles for their applications. Inspired by the semiconductor heterostructure in photocatalysis, we rationally design and precisely synthesize MOFs based heterostructures, in which the TiO2 nanoclusters are filled into the pores of Cu-TCPP nanosheets (i.e. TiO2 NCs@Cu-TCPP HSs). And the composite materials possess three-dimensional (3D) hierarchical architectures, which have advantages of large surface area, excellent light-absorbing ability and photocatalytic efficiency. Significantly, this novel material displays >99.99 % antibacterial efficiency against E. coli and S. aureus within 30 min and preserves the excellent antibacterial ability during reusing three times, which is superior to recently reported photocatalystic-based antibacterial materials. Our study provides new insights into the energy band engineering for enhanced antibacterial performance, paving a way for designing advanced clinical wound dressings.

Three-dimensional hierarchical carbon architecture of porous carbon derived from cross-linked polycyclophosphazenes as supercapacitor electrode material

Three-dimensional hierarchical carbon architecture of porous carbon derived from cross-linked polycyclophosphazenes as supercapacitor electrode material

Vacancy-Mediated Z-Scheme Heterostructure in SnO2-Decorated Spinel In3-xS4 with Boosted Photocatalytic Activity.

The widespread application of dyes and heavy metals causes increasing environmental pollution. One effective way to mitigate environmental pollution is to use semiconductor photocatalysts for redox purification of pollutants. Heterostructured photocatalysts can reduce the electron-hole recombination rate and improve light utilization. In this work, a novel SnO2/In3-xS4 composite with oxygen vacancy defect-mediated Z-scheme heterostructure is constructed for the first time by a one-pot method, in which SnO2 ultrasmall nanocrystals are decorated on nanopetals of flower-like In3-xS4. Material analyses show that the as-built three-dimensional hierarchical architecture is able to essentially increase the specific surface area and thus the active sites of the products. More importantly, the formation of Z-scheme heterojunction between the oxygen vacancy-induced SnO2 defect level and the In3-xS4 band structure not only promotes the separation of photogenerated charges but also makes them more reactive. Through the optimization of the composition ratio between the two phases, the visible-light-driven photocatalytic reaction rates of rhodamine B degradation and Cr(VI) reduction for the developed SnO2/In3-xS4 composite photocatalyst are 12.8 and 6.3 times of bare In3-xS4 and 32.0 and 76.0 times of bare SnO2, respectively. This work should provide a promising implication for designing new high-performance composite photocatalysts.

Structure tailorable and flexible electrospun Poly(vinylidene fluoride)@WS2 membrane with enhanced hydrogen evolution reaction activity and mechanical properties

The metallic 1T phase layered WS2 was feasible to electrocatalytic hydrogen evolution reaction (HER) compared with its 2H phase. Duo to the intrinsically stabile nature of 2H phase WS2, it is challenging to construct metallic WS2 on flexible polymeric substrate. Herein, a two-step method is proposed for constructing electrospun porous poly (vinylidene fluoride) fibers embedded with metallic WS2 an electrocatalyst. The hybrid catalysts exhibit excellent HER performance, and thanks to distinguished mechanical properties, the flexible electrocatalysts maintain their initial catalytic performance after mechanical twisting. It has been demonstrated by experimentation and COMSOL multiphysics simulations that the identity of catalytic activity not only benefits by the synergistic effect of metallic WS2, but also in favor of the three-dimensional (3D) hierarchical architectures ensuring efficacious and substantial geometric interface for catalyzing the HER. These findings expedite an unique approach to create phase-controlled flexible electrode which facilitates the blueprint of clean energy generation.

Double-Base Plate Cooperative Assembly Strategy for the Construction of Ordered Macro-/Mesoporous Noble-Metal Materials for Enhanced Electrochemical Oxidation of Formic Acid

Herein, we propose a general and mild double-base plate cooperative assembly strategy to synthesize the three-dimensional ordered macro-/mesoporous (3DOM/m) noble-metal materials (including Pd, Pt, and Ru), in which the unique double-base plate can play the role of restricting growth area and effectively stabilizing the porous structure of the noble-metal material. In this synthesis process, poly(styrene-b-acrylic acid) (PS-b-PAA) micelles and polymer colloidal crystals are used as templates for the construction of mesopores and macropores, respectively. By adjusting the particle size of polymer colloidal nanospheres, the size of three-dimensional ordered macropores can be precisely adjusted from 160 to 320 nm. Benefiting from the synergistic effect of hierarchical pore structures, the as-prepared 3DOM/m Pd film exhibits outstanding electrocatalytic performance for formic acid oxidation. These results provide an effective and universal method for the designed synthesis of the three-dimensional hierarchical architecture of high-catalytic-activity noble-metal materials.

Microwave-assisted hydrothermal synthesis of three-dimensional NbOPO4-reduced graphene oxide-carbon nanotube composite for high performance sodium-ion battery anode

Sodium-ion batteries (SIBs) have aroused more and more academic and industrial interest due to their decent electrochemical performance and the cost-effectiveness of sodium (Na) resource. However, fabricating an appropriate anode material with high specific capacity, long-term cycle stability and superior rate capability remains a great challenge. Here, we adopt an efficient microwave-assisted hydrothermal method to prepare layered niobium oxyphosphate (NbOPO4) nanosheets, which grows on the single-walled carbon nanotubes (SWCNT) and reduced graphene oxide (rGO) (NbOPO4-rGO-SWCNT). Benefiting from three-dimensional hierarchical architecture combining NbOPO4 nanosheets with rGO-SWCNT framework with excellent electrical conductivity, NbOPO4-rGO-SWCNT electrode delivers a higher reversible specific capacity (323.2 mAh g−1 at 0.1 A g−1) and superior rate capability (147.9 mAh g−1 at 5 A g−1) than that of NbOPO4 (143.1/43.5 mAh g−1). Ex-situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements further reveal the electrochemical mechanism that reversible reaction between niobium phosphate (NbPO4) and niobium (Nb) occurs after the initial intercalation-conversion reaction, which contributes to the stable reversibility and high-rate capability in the following cycling. This work not only indicates that NbOPO4-rGO-SWCNT can act as a desirable anode material for SIBs, but also provide new insights to material design for niobium oxyphosphate composite.

Porous N-doped Ni@SiO2/graphene network: Three-dimensional hierarchical architecture for strong and broad electromagnetic wave absorption

Electromagnetic wave absorber is critical for reducing increasingly serious electromagnetic wave pollution, however, the development of lightweight and broadband microwave absorbers remains a pressing challenge. We report here the rational design and synthesis of N-doped [email protected]2/graphene composite constructed from 3D interconnected porous graphene network and [email protected]2 core-shell architecture, which fulfills lightweight and broadband requirements while exhibiting highly efficient electromagnetic wave absorption. The porous graphene network, functioning both as lightweight support and dielectric mediator, was synthesized via NaCl template-assisted high-temperature calcination method. Upon uniformly attached with core-shell [email protected]2 on the surface, the resulting abundant heterogeneous interfaces constructed by graphene-Ni and Ni-SiO2 strongly reinforce polarization loss. The presence of low dielectric SiO2 allows facile tuning of the complex permittivity of ternary composite by adjusting coating thickness to balance the attenuation ability and impedance matching. Moreover, further N-doping of graphene assists in the optimization of dielectric loss ability. Taking account of the advantages arising from the porous hierarchical architecture, multiple absorption centers and diverse interfaces, the lightweight composite exhibits an ultra-strong reflection loss (RL) value of - 71.13 dB at 13.76 GHz with a thickness of 2.46 mm and broad effective absorption bandwidth of 7.04 GHz at a low filler content of 15 wt.%. More importantly, the effective absorption range covers 13.28 GHz (4.72–18 GHz) with the optimized thickness of 1.6–5 mm, representing 83% of the whole range of frequencies. Our results demonstrate that the novel 3D porous N-doped [email protected]2/graphene network with hierarchical architecture is a promising candidate for high-performance electromagnetic wave absorption.

Three-Dimensional Hierarchical HRP-MIL-100(Fe)@TiO2@Fe3O4 Janus Magnetic Micromotor as a Smart Active Platform for Detection and Degradation of Hydroquinone.

A novel multifunctional Janus magnetic micromotor was designed and constructed by using MIL-100(Fe)@TiO2@Fe3O4 multicore-shells modified with horseradish peroxidase (HRP) as a smart active platform to realize detection and degradation of hydroquinone (HQ). The obtained micromotor showed a unique three-dimensional (3D) hierarchical architecture with highly exposed active sites and could autonomously move at a speed of 140 ± 7.0 μm·s-1 by O2 bubbles generated from the catalytic decomposition of H2O2 fuel. Benefiting from the combination of active self-propulsive motion, high peroxidase-like activity, tuned heterojunctions with matching band structures, and a 3D hierarchical structure, an effective platform involving dynamically sensitive detection and quick removal of HQ from water was established by using the multifunctional HRP-integrated MIL-100(Fe)@TiO2@Fe3O4 Janus micromotor. The proposed multifunctional Janus magnetic micromotor had advantages of simple and feasible fabrication, sensitive detection and effective photo-Fenton degradation of HQ in a wide pH range of 4-7, and magnetic recycling, revealing potential for environmental remediation applications.

Graphene-encapsulated selenium@polyaniline nanowires with three-dimensional hierarchical architecture for high-capacity aluminum–selenium batteries

The cycling performance of the Al/Se@PANI@G battery can be improved by the high electrical conductivity of graphene sheets and the unique PANI shell, together with the three-dimensional hierarchical architecture of Se@PANI@G.

Dual functions of three-dimensional hierarchical architecture on improving the rate capability and cycle performance of LiNi0.8Co0.1Mn0.1O2 cathode material for lithium-ion battery

The main obstacles in lithium-ion battery are limited by rate performance and the rapid capacity fading of LiNi0.8Co0.1Mn0.1O2 (NCM811). Herein, a novel three-dimensional (3D) hierarchical coating material has been fabricated by in situ growing carbon nanotubes (CNTs) on the surfaces of Ni–Al double oxide (Ni–Al-LDO) sheets (named as LDO&CNT) with Ni–Al double hydroxide (Ni–Al-LDH) as both the substrate and catalyst precursor. The resultant LDO&CNT nanocomposites are uniformly coated on the surfaces of NCM811 by the physical mixing method. The rate capability of the resultant cathode material retains to 78.80% at a current rate of 3C. Its capacity retention increases by 6.7–14.42% compared with pristine NCM811 after 100 cycles within a potential range of 2.75–4.3 V at 0.5C. The improved rate capability and cycle performance of NCM811 are assigned to the synergistic effects between Ni–Al-LDO and CNTs. The hierarchical LDO&CNT nanocomposites coating on the surface of NCM811 avoids the aggregation of conductive CNTs and the stacking of Ni–Al-LDO nanosheets. Furthermore, it accelerates Li+ and electrons shuttle and reduces the reaction of Li2O with H2O and CO2 in air, which results in Li2CO3 and LiOH alkali formation on the NCM811 surface.

Hierarchical flower-like architecture of nickel phosphide anchored with nitrogen-doped carbon quantum dots and cobalt oxide for advanced hybrid supercapacitors

The exploitation of hybrid supercapacitors with excellent electrochemical properties is of great significance for energy storage systems. Herein, a three-dimensional hierarchical flower-like architecture of nickel phosphide (Ni2P) decorated with nitrogen-doped carbon quantum dots (N-CQDs) and cobalt oxide (Co3O4) is constructed by an effective two-step hydrothermal strategy followed by in situ phosphorization process. Introducing N-CQDs with superior electrochemical characteristics can not only induce the formation of N-CQDs deposited nickel hydroxide (Ni(OH)2) flower-like architecture but also significantly enhance the electrochemical features of Ni(OH)2 nanosheets. After combination with Co3O4 nanoparticles and phosphorization treatment, an advanced cathode of Ni2P/Co3O4/N-CQDs with enriched surface phosphate ions is obtained, which possesses an ultra-high capacity of 1044 C g−1 (2088 F g−1) at 1 A g−1 with a splendid rate capacity of 876 C g−1 (1752 F g−1) at 20 A g−1. Moreover, a device assembled by Ni2P/Co3O4/N-CQDs hierarchical flower-like architecture and p-phenylenediamine functionalized reduced graphene oxide (PPD/rGO) nanosheets depicts a commendable energy density of 53.5 Wh kg−1 at 772.9 W kg−1. This work provides a novel hierarchical multi-component electrode material with decent electrochemical capacities for hybrid supercapacitors, which has a broad prospect in energy storage devices.

Design of Hierarchical NiCo2O4 Nanocages with Excellent Electrocatalytic Dynamic for Enhanced Methanol Oxidation.

Although sheet-like materials have good electrochemical properties, they still suffer from agglomeration problems during the electrocatalytic process. Integrating two-dimensional building blocks into a hollow cage-like structure is considered as an effective way to prevent agglomeration. In this work, the hierarchical NiCo2O4 nanocages were successfully synthesized via coordinated etching and precipitation method combined with a post-annealing process. The nanocages are constructed through the interaction of two-dimensional NiCo2O4 nanosheets, forming a three-dimensional hollow hierarchical architecture. The three-dimensional supporting cavity effectively prevents the aggregation of NiCo2O4 nanosheets and the hollow porous feature provides amounts of channels for mass transport and electron transfer. As an electrocatalytic electrode for methanol, the NiCo2O4 nanocages-modified glassy carbon electrode exhibits a lower overpotential of 0.29 V than those of NiO nanocages (0.38 V) and Co3O4 nanocages (0.34 V) modified glassy carbon electrodes. The low overpotential is attributed to the prominent electrocatalytic dynamic issued from the three-dimensional hollow porous architecture and two-dimensional hierarchical feature of NiCo2O4 building blocks. Furthermore, the hollow porous structure provides sufficient interspace for accommodation of structural strain and volume change, leading to improved cycling stability. The NiCo2O4 nanocages-modified glassy carbon electrode still maintains 80% of its original value after 1000 consecutive cycles. The results demonstrate that the NiCo2O4 nanocages could have potential applications in the field of direct methanol fuel cells due to the synergy between two-dimensional hierarchical feature and three-dimensional hollow structure.

Hierarchical Brookite TiO₂-Bi₂MoO6 Nanospheres with Efficient Visible-Light-Driven Photocatalytic Response.

Hierarchical TiO₂-Bi₂MoO6 nanospheres as efficient visible-light responsive photocatalyst are fabricated by dispersing brookite TiO₂ nanorods on the hierarchical Bi₂MoO6 nanospheres, which provides visible-light absorption and large surface area. The morphologies, surface area and light absorption features of as-prepared TiO²-Bi²MoO6 can be rational controlled by varying the loading amount of TiO² nanorods on hierarchical Bi²MoO6 nanospheres. As a result, the TiO²-Bi²MoO6-3 yields 380 ppm CO² production for decomposing 2-propanol at 11 h under visible light irradiation, realizing 4.4 times enhancement of photocatalytic property with respect to pure TiO² nanorods. Moreover, the three-dimensional hierarchical architecture enables the hybrid TiO²-Bi²MoO6 excellent cycling stability.

Nickel-cobalt (oxy)hydroxide battery-type supercapacitor electrode with high mass loading

Transition metal hydroxides have shown high capacity performances when at a small mass loading of active material, while it is still a great challenge to obtain a high capacity performance when the mass loading is high. To maximize the capacity at high mass loading, the microstructure of the electrode should be rationally designed. Herein, we report a nickel–cobalt (oxy)hydroxide composite with three-dimensional hierarchical porous architecture realized by an in-situ electrochemical activation method to trigger the active sites and structural rearrangement. By systematically tuning the pore sizes in the hierarchical structure, an optimal composite delivers a record high areal capacity (34.8 mAh cm−2) and energy density (19.1 mWh cm−2) at the mass loading up to 230 mg cm−2. It gives new insights for preparing high performance electrode materials by a facile method and provides a blueprint for the design of high mass-loading supercapacitors.

Three-dimensional hierarchical Na3Fe2(PO4)3/C with superior and fast sodium uptake for efficient hybrid capacitive deionization

Using Faradaic electrodes instead of carbon electrodes to assemble hybrid capacitive deionization (HCDI) is an effective strategy to solve the shortcomings of traditional carbon-based CDI with low salt adsorption capacity (SAC). Herein, high HCDI desalination performance of Na3Fe2(PO4)3/Carbon-X (NFeP/C-X) is attested by designing and preparing three-dimensional (3D) hierarchical porous architecture via a sol-gel-calcination method. The NFeP nanoparticles with small size are uniformly embedded in interconnected carbon nanosheets, and then a convenient nanochannels and 3D conductive carbon framework is formed. This fine structure can not only improve the interface area between electrode and electrolyte, but also shorten the ion transmission distance and ensure the rapid transfer of ions and electrons, thus achieving ultra-high desalination performance. As expected, the as-prepared NFeP/C-750 shows an ultrahigh SAC of 94.5 mg g−1, an ultrarapid desalination rate of 22.5 mg g−1 min−1 and a stable regeneration desalination ability. In addition, the desalination mechanism and ion diffusion kinetics of the NFeP/C-750 was deeply studied by ex-situ structure analysis, electrochemical characterization and density functional theories (DFT) calculations. These results demonstrate that the NFeP/C-750 with excellent desalination ability is a feasible material and offers great potential for HCDI desalination.

Layered Double Hydroxide-Based Gas Sensors for VOC Detection at Room Temperature.

Miniaturized low-cost sensors for volatile organic compounds (VOCs) have the potentiality to become a fundamental tool for indoor and outdoor air quality monitoring, to significantly improve everyday life. Layered double hydroxides (LDHs) belong to the class of anionic clays and are largely employed for NOx detection, while few results are reported on VOCs. In this work, a novel LDH coprecipitation method is proposed. For the first time, a study comparing four LDHs (ZnAl–Cl, ZnFe–Cl, ZnAl–NO3, and MgAl–NO3) is carried out to investigate the sensing performances. As explored through several microscopy and spectroscopy analyses, LDHs show a morphology characterized by a large surface area and a three-dimensional hierarchical flowerlike architecture with micro- and nanopores that induce a fast diffusion and highly effective surface interaction of the target gases. The fabricated sensors, operating at room temperature, are able to reversibly and selectively detect acetone, ethanol, ammonia, and chlorine vapors, reaching significant sensing response values up to 6% at 21 °C. The results demonstrate that by changing the LDHs’ composition, it is possible to modulate the sensitivity and selectivity of the sensor, helping the discrimination of different analytes, and the consequent integration on a sensor array paves the way for electronic nose development.

Interlayer-Expanded MoS2/N-Doped Carbon with Three-Dimensional Hierarchical Architecture as a Cathode Material for High-Performance Aluminum-Ion Batteries

Aluminum-ion batteries (AIBs) have drawn remarkable attention because of the large capacity, inexpensiveness, and abundance of Al in nature. However, the low capacity and poor cycle life of the cathode materials tremendously hinder their development. The fabrication of interlayer-expanded MoS2/N-doped carbon (MNC) with a three-dimensional (3D) hierarchical tremella structure through a hydrothermal treatment and calcination is described in this work. As cathode materials, MNC shows decent capacity and superior cycle stability. Remarkably, the MNC electrode presents a capacity as high as 191.2 mAh g–1, following 450 cycles with a current density of 0.5 A g–1. Moreover, the MNC electrode presents a specific capacity of 127.5 mAh g–1, following 1700 cycles at 1A g–1, and the associated Coulomb efficiency reaches 99.5%. The unique 3D hierarchical structure and interlayer spacing, which reach up to 0.82 nm, reduce the diffusion path for Al3+, boost the diffusion of Al3+, and provide more active sites. Meanwhile, N-doped carbon is beneficial to promote electronic conductivity and maintaining structural integrity during cycles. The insertion and extraction mechanism of Al3+ in MNC has been put forward and confirmed to understand its outstanding electrochemical performance. This study exhibits a strategy to obtain advanced AIB electrode materials through 3D hierarchical architecture design.

Quick self-assembly of bio-inspired multi-dimensional well-ordered structures induced by ultrasonic wave energy.

Bottom-up self-assembly of components, inspired by hierarchically self-regulating aggregation of small subunits observed in nature, provides a strategy for constructing two- or three-dimensional intriguing biomimetic materials via the spontaneous combination of discrete building blocks. Herein, we report the methods of ultrasonic wave energy-assisted, fast, two- and three-dimensional mesoscale well-ordered self-assembly of microfabricated building blocks (100 μm in size). Mechanical vibration energy-driven self-assembly of microplatelets at the water-air interface of inverted water droplets is demonstrated, and the real-time formation process of the patterned structure is dynamically explored. 40 kHz ultrasonic wave is transferred into microplatelets suspended in a water environment to drive the self-assembly of predesigned well-ordered structures. Two-dimensional self-assembly of microplatelets inside the water phase with a large patterned area is achieved. Stable three-dimensional multi-layered self-assembled structures are quickly formed at the air-water interface. These demonstrations aim to open distinctive and effective ways for new two-dimensional surface coating technology with autonomous organization strategy, and three-dimensional complex hierarchical architectures built by the bottom-up method and commonly found in nature (such as nacre, bone or enamel, etc.).