Hollow Nanocube Research Articles

Lithium-Storage Performance and Mechanism of a (Ni0.5Co0.5)9S8@NC Hollow Nanocube Composite as an Advanced Anode

In this work, the lithium-storage performance and mechanism of a designed (Ni0.5Co0.5)9S8@NC hollow nanocube composite as a rechargeable lithium-ion battery (LIB) anode are investigated. The nanocomposite is composed of a bimetallic sulfide (Ni0.5Co0.5)9S8 core and a surrounding nitrogen-doped carbon shell. It displays a superior electrochemical reactivity with an appealing specific capacity of 724 mAh g–1 at a specific current of 0.5 A g–1 cycled 80 times, as well as attractive stability and rate capability. The quantitative kinetic analysis reveals that the advanced lithium-storage performance is partly derived from the pseudocapacitive contributions. In situ X-ray diffraction (XRD) demonstrates the formation of Ni, Co, and Li2S in the conversion reaction during the initial cycling. Ex situ transmission electron microscopy (TEM) and scanning electron microscopy (SEM) demonstrate the volume expansion of the core (Ni0.5Co0.5)9S8 active material with the essential preservation of the complete (Ni0.5Co0.5)9S8@NC hollow nanocube structure during repeating cycling. Namely, the synergistic effect of the N-doped carbon coating, the rigid hollow nanostructure, and the multiple-electron-transfer conversion reaction of the bimetallic sulfide contributes to the superior lithium-storage performance of the nanocomposite.

Design and fabrication of hollow structured Cu2MoS4/ZnIn2S4 nanocubes with significant enhanced photocatalytic hydrogen evolution performance

The unique architecture is very significant for photocatalysts to achieve high photocatalytic efficiency. Herein, hollow Cu2MoS4/ZnIn2S4 heterostructural nanocubes with intimate-contact interface have been prepared for the first time via a self-template way, which can promote the photocatalysis hydrogen evolution. First, novel hollow structured Cu2MoS4 nanocubes were successfully synthesized using Cu2O as a precursor, then the ZnIn2S4 nanosheets were in-situ grew on the surface of hollow Cu2MoS4 nanocubes. The unique hollow heterostructures have markedly enhanced photocatalytic efficiency, and 15 wt% Cu2MoS4/ZnIn2S4 sample exhibits the highest hydrogen production rate of 8103 μmol·h−1·g−1, which is approximately four times higher than pure ZnIn2S4. The improved photocatalytic performance is mainly attributed to the following two points: (1) the hollow nanocube structure can provide rich active sites and increase light absorption; (2) forming a built-in electric field is conducive to transfer the holes generated by ZnIn2S4 to Cu2MoS4, which can effectively promote charge separation. This work may provide insights for the design of hollow architecture cage materials for high photocatalytic performance.

Natural Activation of CuO to CuCl2 as a Cathode Material for Dual-Ion Lithium Metal Batteries

To meet the rising energy demand for rapidly advancing battery-driven devices, a novel Li/Cl dual-ion battery chemistry based on non-flammable SO2-in-salt electrolyte is receiving significant attention. Herein, we propose a natural-activable CuO hollow nanocube (HNC) cathode material for dual-ion Li metal batteries using SO2-in-salt electrolyte. Natural activation is achieved via spontaneous chlorination of CuO HNCs into an electrochemically active CuCl2 phase upon immersed in a SO2-in-salt electrolyte. The on-site conversion reactions are proposed with the support of thermodynamic calculations; the phase transformations of active materials are confirmed through X-ray diffraction, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy. As a solution to alleviate the volume expansion after chlorination, the HNC structure of CuO allows the resulting CuCl2 cathode material to deliver a reversible capacity up to 262.2 mAh g−1 (894.2 Wh kgCuO−1) with stable cycle performance over 150 cycles. The Li-CuO battery system presented here demonstrates the feasibility of non-flammable, high-energy density Li/Cl dual-ion Li metal batteries as a potential alternative to currently used lithium ion batteries.

Modulating CoFe2O4 nanocube with oxygen vacancy and carbon wrapper towards enhanced electrocatalytic nitrogen reduction to ammonia

Electrocatalytic nitrogen reduction reaction is increasingly deemed as a promising route for massive ammonia synthesis. Herein, hollow bimetallic CoFe2O4 nanocube derived from prussian blue analogue is elaborately wrapped by thin carbon layer and modified by rich oxygen vacancies, achieving splendid ammonia yield rate of 30.97 μg h−1 mgcat.−1 and Faradaic efficiency of 11.65 % at −0.4 V versus reversible hydrogen electrode in 0.1 M Na2SO4. In addition, C@CoFe2O4-x nanocube can withstand long-term and repetitive electrolysis without obvious structure collapse, constituent change and activity decay. The prominent activity is strongly associated with improved nitrogen adsorption and activation, collaboratively benefiting from the intrinsic unoccupied d orbitals of transition metal components, reformative electronic structure by oxygen vacancies and elevated electron injection possibility into the antibonding orbital of nitrogen molecule via conductive carbon wrapper. Both actual experiments and theoretical investigations attest the catalytic activity improvement mechanism, rendering the C@CoFe2O4-x nanocube design strategy efficient and valid.

Surface-seeding secondary growth for CoO@Co9S8P-N heterojunction hollow nanocube encapsulated into graphene as superior anode toward lithium ion storage

Heterointerface plays the key role to adjust and enhance the charge carrier transport behavior of composite electrode materials in Li-ion batteries. However, fabricating heterostructures with suitable band gap and exquisitely distributed architectures is still a challenge to realize excellent electrochemical performance. Herein, heterogeneous CoO@Co9S8-rGO hollow nanocube is prepared via surface-seeding and secondary growth followed by subsequent sulfuration and carbonization processes. In this smart design of hollow CoO@Co9S8-rGO heterointerface architecture, the built-in electric field between CoO and Co9S8 helps to quicken the Li-ions transport in lithiation and delithiation processes. The abundant CoO-Co9S8 heterointerface exposes more active sites and facilitatesthe infiltration of electrolyte and Li-ion storage. In-situ generated CoO nanosheet could be a bridge between Co9S8 nanocube and graphene which endows the excellent electron transport channel. As expected, the CoO@Co9S8-rGO electrode exhibits a remarkable reversible discharge capacity (912 mAh g−1 at 0.1 A g−1), high rate performance (586 mAh g−1at 5 A g−1), and excellent cycling stability (600 mAh g−1 at 1 A g−1 after 500 cycles). This work provides an effective strategy for constructing heterostructure anode to enhance the Li-ion transfer and storage.

High-Sensitive MEMS Hydrogen Sulfide Sensor made from PdRh Bimetal Hollow Nanoframe Decorated Metal Oxides and Sensitization Mechanism Study.

Here we report the fabrication of a high performance metal oxide semiconductor (MOS) sensor for the detection of hydrogen sulfide (H2S) using PdRh bimetal hollow nanocube (HC) with Rh-rich hollow frame and Pd-rich core frame as sensitizing materials. PdRh bimetal HC with the edge-length about 10 nm was prepared by chemical etching PdRh bimetal solid nanocube (SC) in HNO3 aqueous solution. The results of gas-sensing tests indicate that the response value order of the MEMS gas sensors based on MOSs (including ZnO, MoO3 and SnO2) is as follows: RPdRhHC/MOS > RPdRhSC/MOS > RMOS. First, in the system of ZnO, gas sensor modified by PdRh (PdRh SC/ZnO and PdRh HC/ZnO) possess enhanced H2S sensing performance with a better response and excellent low-concentration detection capability (down to 15 ppb) comparing to pure ZnO. The improved H2S sensing performance could be attributed to the good conductivity of Rh-rich frame, the high catalytic activity of PdRh bimetal and formation of Schottky barrier-type junctions and defect. Second, PdRh HC/ZnO sensor shows better response (185-1 ppm of H2S) compared to PdRh SC/ZnO sensor (108-1 ppm of H2S), which is due to the higher specific surface area of PdRh HC/ZnO and good gas diffusion of the hollow structure. This work indicate that the sensitization characteristics of PdRh bimetal HC will provide new paradigms for the future development of the high performance sensor.

In Situ Growth of Hollow Trimetallic Nanocubes on Nickel Foam for the Electrocatalytic Oxygen Evolution Reaction

AbstractNanomaterials derived from Prussian blue (PB) and its analogues (PBAs) possess uniform active centers and large surface areas, which can be applied in the field of electrocatalysis. In this study, nickel‐iron‐cobalt trimetallic PBAs, that is, NiFeCo(4 : 1)PBA nanocubes, were grown in situ on nickel foam (NF), which was subsequently calcined in air to obtain a composite electrode, NiO/FeOX/Co3O4@NF, with a loose porous hollow nanocube morphology. This structure remarkably enlarged the contact area between the electrolyte and the catalyst. In addition, a synergistic effect among these metallic oxides expedited oxygen evolution reaction (OER) kinetics. The Tafel slope (71.25 mV dec−1) toward OER of the constructed electrode is fairly small, much lower than that of our prepared bimetallic oxides@NF electrodes. The enduring stability is more than 22 h. This work indicates that, through morphology and composition control, the electrocatalytic performance of the designed electrode can be effectively improved.

Investigation of the Extinction Spectra of a Plasmonic Noble-Metal Hollow Nanocube

In this work, a hollow cubic nanostructure based on noble metals of silver and gold is studied. The extinction spectra of the plasmonic hollow cube are numerically calculated via the finite-difference time-domain method. A two-peak feature is witnessed in the extinction spectra, and the electric fields at the two resonance wavelengths are computed, indicating two different electromagnetic modes. The resonance wavelengths, the full widths at half maximum, and the peak intensities are also determined from the extinction spectra. In the calculations, the structural parameters of the hollow nanocube are systematically varied, including the cubic size, the thickness of the metallic wall, the geometric ratio of the cube, and the dielectric constants of the inner and outer surrounding media. With changing the structural parameters, the trends revealed in the simulated extinction spectra highlight a great tunability in the plasmonic resonances. Based on the results shown in this work, it is suggested that the proposed metallic hollow nanocube be implemented in designs of plasmonic devices.

Boosting Potassium Storage Performance of the Cu2S Anode via Morphology Engineering and Electrolyte Chemistry.

Transition metal sulfides (TMSs) have been demonstrated as attractive anodes for potassium-ion batteries (KIBs) due to the high capacity, abundant resource, and excellent redox reversibility. Unfortunately, practical implementation of TMSs to KIBs is still hindered by the unsatisfactory cyclability and rate performance which result from the vast volume variation during charge/discharge processes. Herein, a uniform nitrogen-doped carbon coated Cu2S hollow nanocube (Cu2S@NC) is designed as an anode material for the KIB, which displays an outstanding cycle performance (317 mAh g-1 after 1200 cycles at 1 A g-1) and excellent rate capacity (257 mAh g-1 at 6 A g-1) in a half-cell. The hollow nanosized structure can both shorten the diffusion length of potassium ions/electrons and buffer the volume expansion upon cycling. Besides, the high concentration electrolyte is beneficial to form the stable solid electrolyte interphase (SEI) film, reducing the interface impedance and enhancing the cycling stability. Ex situ transmission electron microscopy (TEM) and ex situ X-ray diffraction (XRD) reveal the reaction mechanism of Cu2S@NC.

Highly efficient Cu/CeO2-hollow nanospheres catalyst for the reverse water-gas shift reaction: Investigation on the role of oxygen vacancies through in situ UV-Raman and DRIFTS

Self-assembled CeO2 with 3D hollow nanosphere, nanoparticle and nanocube morphologies were prepared and used to support Cu particles. The obtained samples (denoted as Cu/CeO2-hs, Cu/CeO2-np and Cu/CeO2-nc, respectively) were tested for the reverse water-gas shift (RWGS) reaction. Under the reaction conditions, V(H2):V(CO2) = 3:1 and weight hourly space velocity (WHSV) = 300,000 mL g−1 h−1, the Cu/CeO2-hs sample exhibited the best catalytic performance among the as-prepared catalysts. In order to reveal the key factors affecting the catalytic performance, the physicochemical properties of the catalysts were analyzed by XRD, BET, SEM, TEM, H2-TPR, quasi in-situ XPS and in situ UV-Raman techniques. The results point out that the particle size of Cu is not the rate-determining factor while the amount of surface oxygen vacancies is highly correlated with the catalytic reaction rate. In situ UV-Raman and in situ DRIFTS experiments indicate the formation of bidentate carbonate and formate species on oxygen vacancy sites which is thought to be the key intermediates for the RWGS reaction. These findings unravel the crucial roles of surface oxygen vacancies on CO2 adsorption and activation and also highlight a feasible way for the design of highly efficient catalysts for the important RWGS reaction in chemical industry.

Palladium/Copper Alloy Hollow Nanocubes Supported on Sulfur‐doped Graphene as Highly Efficient Catalyst for Ethylene Glycol Oxidation

AbstractTo control and regulate both the shape and size of metal nanoparticles is essential for the design and preparation of active and stable catalysts for fuel cell reactions such as the ethylene glycol (EG) electrooxidation reaction, which is highly sensitive to the structure of the catalysts. We report the synthetic strategy of PdCu alloy hollow nanocube supported on sulfur‐doped graphene (H‐PdCu/SG) catalyst through a self‐assembled hydrothermal process for ethylene glycol (EG) electrooxidation reaction. The as‐prepared hollow PdCu alloy nanocubes are well distributed on the SG surface with a relatively small particle size distribution. Additionally, the H‐PdCu/SG catalyst shows a superior electrocatalytic activity and stability toward EG oxidation.

Synthesis and Operando Sodiation Mechanistic Study of Nitrogen‐Doped Porous Carbon Coated Bimetallic Sulfide Hollow Nanocubes as Advanced Sodium Ion Battery Anode

AbstractDue to the obvious advantages of utilizing naturally abundant and low cost sodium resources, sodium ion batteries (SIBs) show great potential for large‐scale energy storage applications. And the high theoretical capacities of transition metal sulfides (TMSs) make them appealing anode materials for SIBs; however, structural collapse caused by the severe volume change during de/sodiation processes results in poor capacity retention and rate capabilities. Compared to the development of new materials and the improvement of their electrochemical performance, the studies on their reaction mechanisms are still rare, especially the operando characterizations. Herein, the synthesis, anode application, and the operando observation of the de/sodiation mechanism of a nitrogen‐doped porous carbon coated nickel cobalt bimetallic sulfide hollow nanocube ((Ni0.5Co0.5)9S8@NC) composite are reported. Such a material is synthesized via facile sulfidation of phenol formaldehyde coated Ni3[Co(CN)6]2 metal–organic framework precursors with Na2S followed by calcination. The nanocomposite displays a remarkable specific capacity of 752 mAh g−1 at 100 mA g−1 after 100 cycles and outstanding rate capability due to the synergistic effect of several appealing features. Particularly, the pseudocapacitive effect appears to substantially contribute to the sodium storage capability. Operando X‐ray diffraction reveals the conversion reaction mechanism of (Ni0.5Co0.5)9S8@NC, forming Ni, Co, Na2S, and Na2S5.

Core-shell gold @silver hollow nanocubes for higher SERS enhancement and non-enzymatic biosensor

Here we report a simple low-cost method to produce surface-enhanced Raman scattering (SERS) substrates with improved efficiency and high sensitivity towards uric acid and ascorbic acid sensing using non-enzymatic amperometric electrochemical method. Trisoctahedral gold (Au) core-silver (Ag) shell cubical shaped nanoparticles were synthesized simply by varying the surfactant in the reaction medium, and afterwards we made them hollow by galvanic displacement reaction. Spherical core-shell nanoparticles (both solid and hollow) were also prepared to compare results with cubical one. We have performed transmission electron microscopy (TEM) studies to understand the morphology of these nanoparticles and UV–vis–NIR and Raman spectroscopy studies to understand optical properties. We have obtained a huge SERS enhancement (~109) for hollow Au@Ag nanocube using 4-mercapto benzoic acid (4-MBA) as analyte. Because of the very thin Ag shell wall, both core Au and shell Ag interacts with the incoming electromagnetic wave, and also due to the presence of multiple sharp edges and corners in both core and shell part of the nanoparticles there is a large enhancement of the electromagnetic field. We have performed cyclic voltammetry study using the nanoparticles as electrode to understand how interfacial charge transfer and electron accumulation is happening in between an electrode and electrolyte interface and we have obtained a very high current response for hollow core-shell nanocube due to more surface area. High current response with voltage enable us to use hollow core-shell nanocubes as non-enzymatic electrochemical sensor for sensing uric acid (UA) and ascorbic acid (AA). We found a good sensitivity (1.509 μAmM−1cm−2 and 209.027 μAmM−1cm−2 for UA and AA, respectively) and very low detection limit (0.36 μM and 0.019 μM for UA and AA, respectively) towards sensing, which allows us to use Au@Ag hollow nanocube as a good UA and AA sensors.

Enhanced single-band red upconversion luminescence of α-NaErF4:Mn nanoparticles by a novel hollow-shell structure under multiple wavelength excitation

Upconversion nanoparticles (UCNPs) doped with lanthanide ions have potential applications in biomedical, solar cells and displays. However, the intensity of the upconversion luminescence (UCL) is limited by the surface effects of nanomaterials, lattice defects, etc. Here, a novel α-NaErF4 hollow nanocube is fabricated by using divalent manganese ions (Mn2+) to substitute trivalent erbium ions (Er3+) in the NaErF4 matrix. The hollow-shell structure can weaken the luminescence quenching and surface quenching effects, reduce the energy loss of higher energy levels in nanoparticles, and improve the light capture ability of nanoparticles. So the UCL of α-NaErF4 hollow nanocubes is greatly improved, which is 14, 790 and 1071 times higher than that of the β-NaErF4 under 808, 980 and 1530 nm laser excitation, respectively, and the emission in the red region is enhanced respectively by 69, 2049 and 2902 times. In particular, the hollow nanocubes emit intense single-band red emission under the three different wavelengths, respectively. Moreover, the magnetization of α-NaErF4 hollow nanocubes is 2.16 emu g−1 at room temperature, which is larger than that of gadolinium-based materials. Hollow-shell structure, excellent paramagnetism and single-band red upconversion emission excited by various wavelengths will create NaErF4:40Mn UCNPs a good application prospect in the biomedical field.

Hollow copper sulfide nanocubes as multifunctional nanozymes for colorimetric detection of dopamine and electrochemical detection of glucose

Nanozymes have fascinated increasing attention in the field of artificial enzyme. Designing an ideal nanozyme usually requires a synergic advantage of reasonable nanostructures and large specific surface area for ensuring excellent mimicking-enzyme catalytic activity. Here we report a CuS nanozyme with hollow nanocube structure (h-CuS NCs), which has a large surface area of 57.84 m2 g−1, and thus realizes excellent mimicking-enzyme catalytic activity. Expectedly, our directed design of h-CuS NCs nanozymes has an affinity for H2O2 of 0.94 mM, which is outstanding among the state-of-the-art Cu-based nanozymes. Furthermore, this nanozyme acts as a multifunctional catalyst to induce luminol chemiluminescence and oxide 3, 3′, 5, 5′-tetramethylbenzidine (TMB) in the presence of H2O2, and displays distinguished electrocatalytic activity to glucose oxidation. More intriguingly, the nanozyme can produce a promising photothermal effect under the illumination of near-infrared light. This work will provide a prototype for rational design of distinct nanostructures as multifunctional nanozymes in the area of electrochemical sensing, mimicking-enzyme catalytic biosening and cancer therapy.

Morphology Controllable Synthesis of NiO/NiFe2O4 Hetero-Structures for Ultrafast Lithium-Ion Battery.

Rational design of high performance anode material with outstanding rate capability and cycling stability is of great importance for lithium ion batteries (LIBs). Herein, a series of NiO/NiFe2O4 hetero-structures with adjustable porosity, particle size, and shell/internal structure have been synthesized via a controllable annealing process. The optimized NiO/NiFe2O4 (S-NFO) is hierarchical hollow nanocube that is composed of ~5 nm subunits and high porosity. When being applied as anode for LIBs, the S-NFO exhibits high rate capability and excellent cycle stability, which remains high capacity of 1,052 mAh g−1 after 300 cycles at 5.0 A g−1 and even 344 mAh g−1 after 2,000 cycles at 20 A g−1. Such impressive electrochemical performance of S-NFO is mainly due to three reasons. One is high porosity of its hierarchical hollow shell, which not only promotes the penetration of electrolyte, but also accommodates the volume change during cycling. Another is the small particle size of its subunits, which can effectively shorten the electron/ion diffusion distance and provide more active sites for Li+ storage. Besides, the hetero-interfaces between NiO and NiFe2O4 also contribute toitsfast charge transport.

A hollow CuS nanocube cathode for rechargeable Mg batteries: effect of the structure on the performance

Hollow CuS nanocubes are used as rechargeable Mg battery cathodes with fast solid-state Mg2+ ion diffusion kinetics.

Hollow CuS nanocube as nanocarrier for synergetic chemo/photothermal/photodynamic therapy

Here, hollow CuS nanocubes about 250–300 nm in size were synthesized based on the Kirkendall effect by using CuO nanocubeas precursor and template. The reactant concentration and reaction time could be adopted to adjust the final composition and hollow structure. The as-synthetic CuS nanocube was assembled by a great deal of nanoparticles (15–20 nm), making abundant porous structure in the shell layer. The localized surface plasmon resonance and the novel porous hollow structure (improve light reflex) further make sure the enhanced Near-infrared (NIR) light absorption as well as photothermal conversion efficiency (30.3%). Moreover, the mechanism of reactive oxygen species (ROS) generation was investigated in detail, revealing that the released Cu+ ion and the oxygen are the determined factors. To further improve the monodispersity and biocompatibility, PEG-NH2 modified nanostructure (CuS@PEG) was prepared and it possessed high loading efficiency to doxorubicin hydrochloride (DOX). Moreover, DOX-CuS@PEG reveals the acid and NIR sensitive-release performance. The synergistic effect of chemotherapy associated with photothermal therapy (PTT) and photodynamic therapy (PDT) display the enhanced specific cytotoxicity to cancer cells.

Synthesis of AuAg@Ag core@shell hollow cubic nanostructures as SERS substrates for attomolar chemical sensing

Electrum, the AuAg bimetallic alloy, has been an important system since ancient times to the present day, as these alloys have bi-functional properties lacking from their constituent metallic elements. We report a simple synthesis of a novel AuAg@Ag core@shell nanostructure (NS), where a bimetallic AuAg alloy hollow nanocube (HNC) core was coated with a monometallic Ag shell. The AuAg hollow cubic NSs were synthesized through a direct, one-pot synthetic protocol using Tween 80 micelles, a non-ionic surfactant, as a soft-template. The core@shell NSs were prepared from Ag and ascorbate ions under alkaline conditions in the presence of AuAg HNC as the core. The atomic percent of Ag in the core-shell NS was varied by using different amounts of the feed Ag ions during the synthesis. Depending on the Ag nanoparticle coating, the localized surface plasmon resonance (LSPR) peak of the AuAg@Ag core-shell hollow cubic NS underwent significant blue-shifting and narrowing. The necessity for such a AuAg alloy core and Ag-shell NS was demonstrated via surface-enhanced Raman scattering (SERS) studies performed using 4-mercaptothiophenol (4-MPh) as a probe molecule. Moreover, the sensitivity of the AuAg@Ag core-shell NSs as effective SERS substrates was revealed via concentration-dependent SERS studies on 4-MPh (up to 1 aM). In this work, the importance of electronic ligand effects associated with charge transfer from the AuAg alloy core through the Ag shell to the probe molecule has been highlighted using the commonly studied 4-aminothiophenol.

Composition-Dependent Electrocatalytic Activity of Cobalt Sulfides for Triiodide Reduction in Dye-Sensitized Solar Cells

A new nanoarchitecture of cobalt sulfide (CoSx) is designed by exploiting a Prussian blue analogue. Depending on the sulfidation temperatures, CoSx materials with different compositions and morphologies are obtained. This investigation of the composition-dependent electrocatalytic activity of CoSx for triiodide reduction reaction (IRR) reveals that sulfur-deficient CoSx is more active than sulfur-rich CoSx. When utilized in dye-sensitized solar cells (DSSCs), sulfur-deficient CoSx with a hollow nanocube morphology outperforms platinum (Pt), showing great promise as a Pt alternative. This composition dependency on IRR is attributed to different surface characteristics and electrical properties that vary with CoSx composition. This work highlights the importance of understanding the surface properties of sulfide-based electrocatalysts that are intimately dictated by their compositions as part of a new design principle for a highly active electrocatalyst.