3D Hollow Research Articles

Facile fabrication of poly (diallyldimethyl ammonium chloride)/Ti3C2Tx/poly (vinylidene fluoride) 3D hollow fiber membrane flexible humidity sensor and its application in the monitoring of health-related physiological activity

Flexible humidity sensors could be integrated with intelligent terminals, small medical devices, flexible electronic skin, etc. to monitor human physiological activity and safeguard the health. Herein, we report the facile preparation of flexible humidity sensors based on the composite of poly (diallyldimethyl ammonium chloride) (PDDA) and Ti3C2Tx loaded on the substrate of 3D hollow fiber membranes of poly (vinylidene fluoride) (PVDF) by pressure filtration and immersion deposition. The composite sensors of PDDA/Ti3C2Tx/PVDF showed high sensitivity (impedance change of three orders of magnitude between relative humidity (RH) of 10% and 90%), good sensing linearity (R2 = 0.997), relatively small hysteresis (∼5% RH), outstanding selectivity, stable humidity response under deformation and good long-term stability. Moreover, they could recognize respiration status and identify movement of fingertip as slight as 1 mm, suggesting potentials in healthcare and human-machine interaction. The high performance of the composite sensor is attributed to large specific surface area and good conductivity of Ti3C2Tx, high sensitivity of PDDA, and abundant microporous and hollow channels in PVDF fiber membrane for efficient transport of moisture. The work offers new approaches for preparing advanced flexible sensors with promising prospects in wearable electronics.

High-Performance flexible Quasi-Solid-State aqueous Nickel-Iron battery enabled by MOF-Derived N-Doped carbon hollow nanowall arrays

The development of portable, flexible and wearable electronic devices has accelerated ever-growing demand for high-performance power sources with high specific energy/power density, high-level safety, low cost, and highly flexible features. Herein, a flexible quasi-solid-state aqueous nickel–iron (QSSA Ni-Fe) battery with high energy and power densities is rationally developed using ultrathin Ni(OH)2 nanoflakes and porous ɑ-Fe2O3 nanorods conformally deposited on vertically aligned MOF-derived N-doped carbon hollow nanowalls supported by carbon textiles (NC/CTs) as the cathode (Ni(OH)2@NC/CTs) and anode (ɑ-Fe2O3@NC/CTs), respectively. The obtained flexible QSSA Ni-Fe battery delivers optimal electrochemical performance, including high energy density (155.4 Wh Kg−1), high power density (14.0 KW Kg−1) and excellent cycling stability (∼86.1 % retention after 10,000 cycles). Impressively, the flexible QSSA Ni-Fe battery delivers stable electrochemical performance even under different bending conditions. The excellent electrochemical properties may be attributed to the following reasons: (i) The ultrathin Ni(OH)2 nanoflakes and porous ɑ-Fe2O3 nanorods deposited on 2D hollow NC arrays possess a high porosity and large specific surface area; (ii) The 2D hollow NC arrays on flexible CTs not only increase the electrical conductivity, but also function as a scaffold to hold the active materials (such as Ni(OH)2 or ɑ-Fe2O3) and thus maintain the structural integrity of the composites. This work provides a novel approach to design and develop QSSA batteries with satisfactory electrochemical properties and excellent flexibility, and have greater potential for future flexible and wearable electronic devices.

Synergistic effect and nanostructure engineering of three-dimensionally hollow mesoporous spherical Cu3P/TiO2 in aqueous/flexible Zn–air batteries

Designing materials with electron/mass transfer effectively improves catalytic activity by synergistic effects between different species. Herein, we report a high-temperature pyrolysis strategy to induce charge transfer of Cu3P loaded TiO2 3D hollow mesoporous carbon nanospheres (Cu3P/TiO2@NC). Density functional theory (DFT) calculations disclose that synergistic between Cu3P and TiO2 can optimize the adsorption of oxygen intermediates and endow fast reaction kinetics. Cu3P/TiO2@NC with hollow mesoporous structure can establish a favorable three-phase interface and shorten the electronic/mass transport path to accelerate reaction kinetics. Consequently, Cu3P/TiO2@NC indicated robust electrocatalytic activity in alkaline medium compared to single-component catalysts and benchmark Pt/C. Cu3P/TiO2@NC exhibits a greater power density of 182.9 mW cm−2 and excellent cyclability over 220 h than Pt/C + RuO2 in Zn-air battery. The flexible properties endow Cu3P/TiO2@NC with promising application prospects in wearable electronic devices. This work may provide an avenue to construct hollow-porous-structured catalysts with synergistic effects for renewable energy devices.

Cover Picture

Cover Picture

Cobalt sulfide nanoparticles restricted in 3D hollow cobalt tungstate nitrogen-doped carbon frameworks incubating stable interfaces for Li-ion storage

Hierarchical nanostructures that comprise multiple tiers of structural subunits and diverse chemical components can provide more active storage sites and relieve the micro-strain due to volumetric change than solid structures in LIBs. In this work, we designed the facile preparation of a yolk-shell structure based on Ostwald ripening for steady lithium-ion storage with Co9S8@CoWO4/nitrogen-doped carbon nanohybrids (YS-Co9S8@CoWO4-NC) as anodes. This yolk-shell configuration design not only accelerated the diffusion of lithium-ion during the lithiation process but also constructed stable interfaces for achieving more steady cycling. It consequently delivered long cycle stability (780 mAh·g−1 after 250 cycles at 1000 mA·g−1) and excellent rate capacities (1023, 767 mAh·g−1 at 100, 2000 mA·g−1, respectively). Furthermore, in-situ electrochemical impedance spectroscopy was successfully implemented to monitor interface properties by simultaneously recording the impedance during discharging and charging processes. The incubating of stable interfacial layers was further confirmed by ex-situ SEM. These results fully affirmed the contribution of hierarchical nanostructures to the construction of stable interfaces, achieving long cycle Li-ion storage.

Hollow-structured amorphous Cu(OH)x nanowires doped with Ru for wide pH electrocatalytic hydrogen production

Developing efficient and stable catalysts for electrocatalytic hydrogen evolution reaction (HER) with low overpotential is the key point to realizing large-scale hydrogen commercialization. Herein, Ru doped amorphous hollow copper hydroxide nanowires on copper foam (Ru-Cu(OH)x/CF) is prepared by surface chemical oxidization and following solvothermal process. The hollow 3D nanowire structure can provide abundant accessibility active sites, promote electrolyte in filtration and facilitate gas diffusion in the process of the electrochemical reaction. Then, the as-synthesized Ru-Cu(OH)x/CF electrocatalyst exhibits impressive electrocatalytic performance for HER with 45, 80 and 50 mV to drive 10 mA cm−2 in 1.0 M KOH, 1.0 M phosphate-buffered saline (PBS) and 0.5 M H2SO4, respectively, with remarkable long-term stability. Moreover, sustainable energies can power the two-electrode setup with amounts of hydrogen generation. The strategy may be particularly beneficial to explore simple synthesis and high-performance catalysts for HER.

Structure and surface modification of MXene for efficient Li/K-ion storage

In this paper, three-dimensional (3D) hollow Ti3C2Tx MXene tubes (HTCTs) with more –O terminal groups and fewer –F groups are successfully prepared via the template-oriented electrostatic self-assembly and the subsequent annealing treatment. The obtained 3D hollow structure with large specific surface area, unique porous structure, and enlarged interlayer spacing could prevent the re-stacking of two-dimensional (2D) sheets and shorten the diffusion pathway of ions. Furthermore, density functional theory (DFT) calculations and electrochemical tests reveal that Ti3C2O2 MXene possesses higher adsorption ability and lower diffusion barrier for K+ and Li+ compared to Ti3C2 MXene dominated by –F terminal groups. Benefiting from the synergistic effect of the structural design and surface modification, the as-prepared 3D HTCTs exhibit excellent electrochemical performance as anodes for K+ and Li+ storage compared with 2D Ti3C2Tx sheets (TCSs).

Ultralong cycle life and high rate sodium-ion batteries enabled by surface-dominated storage of 3D hollow carbon spheres

Carbon materials are considered as prospective candidates for Na-ion batteries (SIBs) anodes, which have attracted significant attention. It is critical to develop a novel carbon anode with high specific capacity and excellent coulombic efficiency for practical application of SIBs. Herein, N/S-codoped hollow carbon spheres with rich carbon nanotubes is developed to work as sodium ion batteries anode. Owing to the unique structure, the material exhibits excellent performance and cycling stability at ultrahigh rate. In addition, the capacity maintains at 130 mA h g-1 under a current density of 10 A g-1 after 5600 cycles. The mechanisms of surface-dominated storage are elaborated by electrochemical test, scanning transmission electron microscopy, X-ray photoelectron spectroscopy, Raman analysis, ex situ X-ray diffraction. Furthermore, we quantitatively calculate the relationship between the extra specific capacity and the introduced defect, which can give the inspiration of improving the performance of sodium ion batteries. These results benefit the development of novel excellent sodium storage materials.

Camphene-derived hollow and porous nanofibers decorated with hollow NiO nanospheres and graphitic carbon as anodes for efficient lithium-ion storage

A synthesis strategy for hollow and porous nanofibers comprising hollow NiO (H-NiO) nanospheres formed via nanoscale Kirkendall diffusion and supported over a porous graphitic carbon matrix (H-NiO@HNFs) is reported herein to enable the fabrication of advanced anodes for stable lithium-ion batteries (LIBs). The H-NiO@HNFs comprising 1D longitudinal hollow channels ensured efficient diffusion of charged species via effective electrolyte percolation besides providing sufficient space to accommodate the large volume variations during repeated cycling. The hollow NiO nanospheres acted as chemical sites for lithiation and delithiation. Additionally, the H-NiO@HNFs exhibited improved lithium-ion storage properties, such as reasonable rate capability, stable prolonged cyclability at a high current density (1.0 A g-1), and a high lithium-ion diffusion coefficient, primarily owing to their enhanced structural integrity compared to that of filled NiO nanofibers (F-NiO NFs). This facile synthesis approach could broaden the current understanding of 1D hollow nanostructures decorated with conventional hollow metal-oxide nanoparticles for various applications.

Protrusion-Rich Cu@NiRu Core@shell Nanotubes for Efficient Alkaline Hydrogen Evolution Electrocatalysis.

The development of highly efficient and durable water electrolysis catalysts plays an important role in the large-scale applications of hydrogen energy. In this work, protrusion-rich Cu@NiRu core@shell nanotubes are prepared by a facile wet chemistry method and used for catalyzing hydrogen evolution reaction (HER) in an alkaline environment. The protrusion-like RuNi alloy shells with accessible channels and abundant defects possess a large surface area and can optimize the surface electronic structure through the electron transfer from Ni to Ru. Moreover, the unique 1D hollow structure can effectively stabilize RuNi alloy shell through preventing the aggregation of nanoparticles. The synthesized catalyst can achieve a current density of 10mA cm-2 in 1.0 m KOH with an overpotential of only 22mV and show excellent stability after 5000 cycles, which is superior to most reported Ru-based catalysts. Density functional theory calculations illustrate that the weakened hydrogen adsorption on Ru sites induced by the alloying with Ni and active electron transfer between Ru and Ni/Cu are the keys to the much improved HER activity.

(Invited) Kinetics and Thermodynamics of Swcnts and Bnnts Encapsulation with α-Sexithiophene in Liquid Phase

Single-Walled Carbon Nanotubes (SWNTs) and Boron Nitride Nanotubes (BNNTs) come with hollow 1D centers, which can serve to define narrow spaces for encapsulating small organic dyes. The encapsulation process is of scientific interest because it can be used to tailor the optical properties of the resulting dyes@NTs nanohybrids. Past works have shown that the dyes@SWCNT exhibits a strongly enhanced Raman scattering cross section, while the dyes@BNNTs do emit robust, generally red-shifted, luminescence at wavelengths down to the near-IR. In both cases, the nanotube protects the encapsulated dyes from photobleaching, provides high confinement, and reinforces intermolecular interactions between dyes into specific aggregation states.Here, we compare the liquid phase encapsulation process of α-sexithiophene (6T), which is a conjugated rod-like dye, inside SWCNTs and BNNTs. Raman and luminescence imaging experiments are used to monitor the 6T encapsulation process of a large ensemble of individual nanotubes in liquid-phase. This method probes statistically the encapsulation kinetics using hundreds of individual nanotubes according to various parameters (dye concentration and temperature). The results highlight a kinetic model in which single and double aggregates is formed sequentially. This kinetics and the associated thermodynamic parameters for the 6T encapsulation will be presented and discussed so as to gain a better control over the emission properties of the nanohybrids.

In-plane benzene incorporated g-C3N4 microtubes: Enhanced visible light harvesting and carrier transportation for photocatalytic CO2 reduction

As a promising material for photocatalytic CO2 reduction, graphitic carbon nitride (CN) and its modification has attracted significant attention. In this work, the in-plane benzene incorporated g-C3N4 microtubes were fabricated via a hydrothermal self-assembly and subsequent thermal polymerization. It is revealed that introducing the π electron-rich benzene ring into the planar structure of g-C3N4 can improve the availability of π electron and create the local asymmetry of heptazine structure. As a result, the separation and transportation of photogenerated charges are improved. Furthermore, the modified g-C3N4 possesses relatively narrow band gap and enhances light absorption. When the in-plane benzene modified g-C3N4 microtubes were applied to photocatalytic CO2 reduction with Co(bpy)3Cl2 as co-catalyst, a CO yield up to 322.66 μmol·g−1·h−1 was obtained, which was two times in comparison with the pristine g-C3N4. This work confirms the effectiveness of in-plane benzene modification and 1D hollow structure formation in improving the photoelectric performance of g-C3N4. Besides, it provides an efficient photocatalytic CO2 reduction protocol with nonmetallic semiconductor material and earth-abundant metal co-catalyst.

Distinctive Formation of Bifunctional ZnCoS-rGO 3D Hollow Microsphere Flowers with Excellent Energy Storage Performances

Distinctive Formation of Bifunctional ZnCoS-rGO 3D Hollow Microsphere Flowers with Excellent Energy Storage Performances

Tellurium Nanotubes and Chemical Analogues from Preparation to Applications: A Minor Review.

Tellurium (Te), the most metallic semiconductor, has been widely explored in recent decades owing to its fantastic properties such as a tunable bandgap, high carrier mobility, high thermal conductivity, and in-plane anisotropy. Many references have witnessed the rapid development of synthesizing diverse Te geometries with controllable shapes, sizes, and structures in different strategies. In all types of Te nanostructures, Te with one-dimensional (1D) hollow internal structures, especially nanotubes (NTs), have attracted extensive attention and been utilized in various fields of applications. Motivated by the structure-determined nature of Te NTs, we prepared a minor review about the emerging synthesis and nanostructure control of Te NTs, and the recent progress of research into Te NTs was summarized. Finally, we highlighted the challenges and further development for future applications of Te NTs.

Highly permeable composite nanofiltration membrane via γ-cyclodextrin modulation for multiple applications

The treatment of pharmaceutical wastewater has become a worldwide problem. Highly efficient treatment for wastewater is extremely critical for ecological environment. Herein, a thin-film nanofibrous composite (TFNC) nanofiltration (NF) membrane modulated by γ-cyclodextrin (γ-CD) was prepared via interfacial polymerization. The γ-CD and piperazine (PIP) were adopted and acting as the mixed reaction monomers in aqueous phase for the fabrication of the separation layer. Not only PIP, γ-CD units would also react with organic phase trimesoyl chloride (TMC) at the interface and participate into the polymerization network. Compared with pure polyamide TFNC membranes, the γ-CD modulated TFNC membranes demonstrated thinner skin thickness. Owing to the 3D hollow structure of γ-CD, the self-contained through cavities would provide additional direct nanochannels to facilitate the water transport. Under 0.5 MPa, the optimized PIP0.5γCD0.5 and PIP0.5γCD1.5 TFNC membranes showed much higher permeate flux of 23.27 and 26.34 L m-2h−1 bar−1, respectively, than that of pure polyamide membranes (9.13 and 9.85 L m-2h−1 bar−1) and the Na2SO4 rejection remained high (>98.7%). Moreover, both TFNC membranes exhibited extremely high rejection (>99%) for several pharmaceuticals (doxycycline hydrochloride, tetracycline, and amoxicillin), and the PIP0.5γCD0.5 TFNC membrane exhibited a good separation factor (31.8) for NaCl/tetracycline solution. In addition, both optimized TFNC membranes showed good pressure resistance and long-term operating stability. This research revealed a facile modulation strategy for the fabrication of high-performance NF membrane and indicated the great promise for desalination, pharmaceuticals wastewater treatment and antibiotics concentration.

Coupling surfactants with 3D hollow raspberry-like NiS/carbon microsphere with S vacancies for enhanced sensitivity monitoring of serotonin and L-tryptophan

Serotonin (ST) is a monoamine neurotransmitter synthesized from L-tryptophan (L-Try). Solving their simultaneous detection problem is necessary for assisting in diagnostics diseases. In this work, we designed NiS/carbon hybrids with NiS nanoparticles embedded on 3D hollow porous carbon microspheres (NiS/CS) via successive carbonization and sulfidation Ni-MOF for constructing electrocatalysts for the simultaneous electrooxidation of ST and L-Try. The formation of robust contact with surface S vacancies in NiS/CS nanointerfaces demonstrated a remarkably enhanced electrocatalytic activity towards ST and L-Try and the corresponding electrochemical signals appeared as two well resolved oxidation peaks with the significant peak-to-peak separation. Importantly, the dual amplification effect of the high electrocatalytic performance function of NiS/CS and the hydrophobic properties of surfactant CTAB coupling made CTAB/NiS/CS/GCE exhibit high sensitivity recognition to ST and L-Try, effectively shielding other coexisting interference. The developed sensor provided a 0.01–200.0 μmol/L linear response range and the low detection limit of 3.35 and 2.94 nmol/L for ST and L-Try, respectively. Finally, this sensing methodology enabled accurate determination of ST and L-Try amount in serum, urine and injection samples and with successful recovery outcomes.

Low Heat Capacity 3D Hollow Microarchitected Reactors for Thermal and Fluid Applications

Lightweight reactor materials that simultaneously possess low heat capacity and large surface area are desirable for various applications such as catalytic supports, heat exchangers, and biological scaffolds. However, they are challenging to satisfy this criterion originating from their structural property in most porous cellular solids. Microlattices have great potential to resolve this issue in directing transport phenomena because of their hierarchically ordered design and controllable geometrical features such as porosity, specific surface, and tortuosity. In this study, we report hollow ceramic microlattices comprising a 10 μm thick hollow nickel oxide beam in an octet-truss architecture with low heat capacity and high specific surface area. Our microarchitected reactors exhibited a low heat capacity for a rapid thermal response with a small Biot number (Bi << 1) and large intertwined surface area for homogeneous flow mixing and chemical reactions, which made them ideal candidates for various energy applications. The hollow ceramic microlattice was fabricated by digital light three-dimensional (3D) printing, composite electroless plating, polymer removal, and subsequent thermal annealing. The transient thermal response and fluidic properties of the 3D-printed microstructures were experimentally investigated using a small-scale thermal and fluid test system, and analytically interpreted using simplified models. Our findings indicate that hollow microarchitected reactors provide a promising platform for developing multifunctional materials for thermal and fluid applications.

3D hollow reduced graphene oxide coated TiO2 heterostructures as an advanced host-interlayer integrated electrode for enhanced Li[sbnd]S batteries

Owing to the short of comprehensive and detailed design of both interlayer and sulfur host, the inherent shortcomings of shuttle effect and sluggish redox chemistry of sulfur cathodes makes the capacity of Lithium-sulfur (LiS) batteries decreasing rapidly. Herein, a three-dimensional (3D) hollow heterostructure, constructed by reduced graphene oxide coated hollow TiO2 microspheres (noted as H-TiO2@rGO heterostructures), is developed as progressive host-interlayer integrated electrodes for LiS batteries. It is noteworthy that the hollow TiO2 microspheres provide a applicable space for loading and trapping sulfur nanoparticles, and the shell formed by TiO2 particles ensures enrichment of catalytic active sites, thus effectively trapping and promoting the transformation of soluble polysulfides. The elastic rGO layer can greatly promote the electrical conductivity of S host, as well as to significantly buffer volume expansion during charge/discharge process. Furthermore, the H-TiO2@rGO heterostructures modified integrated electrode can effectively improve the diffusion of lithium ions while preventing the shuttle effect due to the excellent trapping effect to polysulfides and the presence of continuous shell with holes composed of TiO2 small particles. Therefore, the rational designed host-interlayer integrated electrode of H-TiO2@rGO heterostructures not only confine the sulfur/polysulfides in 3D hollow microspheres, but also achieve catalytic transition of the polysulfides dissolved in electrolyte to solid Li2S2/Li2S, both of which synergistically achieves an extremely fading rate of 0.025% per cycle over 1000 times at 1C. The H-TiO2@rGO heterostructures proposed in this paper may supply a fresh idea for the fine design of LiS battery integrated electrodes.

Prussian blue analogue fabricated one-dimensional hollow tube for high-performance detection of glucose

In this work, we resolve a great challenge that Prussian blue analogue (PBA) nanocubes are successfully fabricated into one-dimensional (1D) hollow tube. It is well known that 1D hollow structure is especially attractive for electrochemical sensor due to its special advantages, but it is also an extremely difficult project for PBA because of their classic cubic morphology. Herein, we adopted a two-step synthetic strategy, realizing the successful fabrication of NiFePBA one-dimensional hollow tubes on the surface of nickel foam (NF) as conductive substrate. A series of testing results have demonstrated that as-prepared 1D hollow nanotubes exhibit excellent electrochemical sensing performance towards glucose, including fast response speed of 0.1 s, wide detection range of 2–650 μM, very high sensitivity up to 21.04 mA mM−1 cm−2, and low limit of detection (LOD) of 0.2 μM (S/N = 3). In a word, this work provides excellent electrochemical sensor materials towards glucose, more importantly, it develops a novel and general strategy to construct 1D hollow structure for further application.

Analysis of mechanical response and energy efficiency of a pavement integrated photovoltaic/thermal system (PIPVT)

Photovoltaic pavement technology was introduced several years ago but has not yet reached commercial maturity, and there are still many technical difficulties to be overcome, such as heat dissipation issues. Using PV cells to generate sufficient energy requires high solar insolation, but high temperatures will also reduce its efficiency.Therefore, this research evaluates the potential of a pavement integrated PV/T system (PIPVT), which incorporates photovoltaic/thermal (PV/T) technology into the roads for power and thermal energy harvesting. While solving the heat dissipation problem of the PV pavement, it can also recover the heat that cannot be used by the PV cells. A unit block of hollow structure 3D printed using plastic material with tempered glass as a protective layer and ABS plastic was used in this paper. A 3D computational finite element model (FEM) developed in ABAQUS was used to analyse the mechanical response of the structure, and a laboratory experiment was conducted to test the influence of the heat dissipation method incorporating water filled pipes on the power generation efficiency of PV cells. The results show that the introduced water circulating pipes had a negligible effect on the mechanical response of PV pavement unit blocks; PIPVT can significantly reduce the solar panel's temperature, and the temperature drop can be as high as 22 °C. According to the results, the primary energy-saving efficiency of PIPVT is estimated to be almost twice that of the conventional PV module. Therefore, this study showed the PIPVT had benefits that went far beyond solar energy generation.