Three-dimensional Hierarchical Nanostructures Research Articles

Fabrication of Rhenium Disulfide/Mesoporous Silica Core-Shell Nanoparticles for a pH-Responsive Drug Release and Combined Chemo-Photothermal Therapy.

A stimuli-responsive drug delivery nanocarrier with a core-shell structure combining photothermal therapy and chemotherapy for killing cancer cells was constructed in this study. The multifunctional nanocarrier ReS2@mSiO2-RhB entails an ReS2 hierarchical nanosphere coated with a fluorescent mesoporous silica shell. The three-dimensional hierarchical ReS2 nanostructure is capable of effectively absorbing near-infrared (NIR) light and converting it into heat. These ReS2 nanospheres were generated by a hydrothermal synthesis process leading to the self-assembly of few-layered ReS2 nanosheets. The mesoporous silica shell was further coated on the surface of the ReS2 nanospheres through a surfactant-templating sol-gel approach to provide accessible mesopores for drug uploading. A fluorescent dye (Rhodamine B) was covalently attached to silica precursors and incorporated during synthesis in the mesoporous silica walls toward conferring imaging capability to the nanocarrier. Doxorubicin (DOX), a known cancer drug, was used in a proof-of-concept study to assess the material's ability to function as a drug delivery carrier. While the silica pores are not capped, the drug molecule loading and release take advantage of the pH-governed electrostatic interactions between the drug and silica wall. The ReS2@mSiO2-RhB enabled a drug loading content as high as 19.83 mg/g doxorubicin. The ReS2@mSiO2-RhB-DOX nanocarrier's cumulative drug release rate at pH values that simulate physiological conditions showed significant pH responsiveness, reaching 59.8% at pH 6.8 and 98.5% and pH 5.5. The in vitro testing using HeLa cervical cancer cells proved that ReS2@mSiO2-RhB-DOX has a strong cancer eradication ability upon irradiation with an NIR laser owing to the combined drug delivery and photothermal effect. The results highlight the potential of ReS2@mSiO2-RhB nanoparticles for combined cancer therapy in the future.

Cactus-like (Ni,Co)Se2 nanosheets with 3D structure decorated on the conductive substrate for efficient hydrogen evolution reaction

Transition metal selenides are a fascinating class of substitute for traditional noble metal electrocatalysts for hydrogen evolution reaction (HER). However, the monometallic selenides still have the disadvantages of low electroactive sites and electrical conductivity. To address such drawbacks, three-dimensional (3D) hierarchical nanostructures composed of bimetallic compounds have aroused great attention. In this study, cactus-like bimetallic nickel–cobalt nanosheets with a 3D nanostructure are successfully prepared on the surface of conductive substrate by a one-step hydrothermal reaction. Then a high-efficiency bimetallic catalyst ((Ni,Co)Se2/CFP) is obtained by a facile chemical vapor deposition. Benefiting from bimetallic components and the unique 3D structure, the cactus-like (Ni,Co)Se2/CFP only requires a low overpotential of 154 mV to reach the current density of 10 mA cm−2. The Tafel slope of (Ni,Co)Se2/CFP (67 mV dec−1) further shows that (Ni,Co)Se2/CFP has faster HER kinetics. Besides, the long-term stability test demonstrates the excellent durability of (Ni,Co)Se2/CFP in 0.5 M H2SO4. This research offers a useful technique and guide for improving the structure of bimetallic selenides based on transition metals to design high-efficient HER electrocatalysts.

Tuning the morphologies of ZnO for enhanced photocatalytic activity

Facile one-pot method to prepare three-dimensional hierarchical nanostructures of ZnO with good control over their morphologies and enhanced photocatalytic activity was developed by proper selection of template, base and microwave irradiation conditions in pure water. Synthesized ZnO products were characterized by XRD, SEM, BET, and TGA. The effect of morphology on the decolorization of rhodamine B solution under UV light irradiation was investigated. The ZnO nanorods originating from the center (Tetrapods) exhibits enhanced photocatalytic activity in the degradation of Rhodamine B under UV light irradiation. This high degradation efficiency (98.86 %) can be attributed to the large percentage of the exposed [1 0 1] facet, (facet dependent) even though surface area is relatively lower. Photocatalytic study reveals that the decomposition of Rhodamine B follows a first order kinetics regardless of the morphology of ZnO particles. The rate constant for nano tetrapods of ZnO particles is the highest (0.036 min−1), while the rate constant for nano coral reefs is lowest (0.003 min−1). Moreover, the photocatalyst exhibits excellent durability, allowing it to be utilized for at least five consecutive cycles without losing its efficiency. Based on the results obtained from two separate synthesis and characterization experiments performed under identical reaction conditions, we can conclude that our material and synthesis protocol exhibit a high degree of reproducibility. This study signifies the dependence of enhanced photocatalytic activity on morphology but not the surface area of material.

Hierarchical Cu Nanoarray/NiFe Hydroxide Nanostructures for Efficient Electrochemical Water Oxidation

Three-dimensional (3D) hierarchical nanostructures have shown great promise for electrocatalysis, while a conductive core is paramount to boost the ultimate catalytic activity. In the present study, hierarchical NiFe hydroxide–Cu arrays are prepared through solution etch and sequential electrolysis as the electrocatalysts for oxygen evolution reaction (OER). The electrochemically reduced Cu nanoarrays as the core provide superior conductivity for electron transfer, while the unique hierarchical 3D structure provides a large active surface area, a short ion diffusion path, and open channels for efficient gas release. The resulting NiFe hydroxide–Cu arrays on copper foam (CF) exhibit outstanding catalytic performance of 245 and 300 mV, respectively, to achieve current densities of 10 and 100 mA cm–2 in a 1 M KOH solution. A small Tafel slope of 51 mV dec–1 and superior electrochemical durability of up to 100 h are also demonstrated.

Cost-effective dye-sensitized solar cells based on rutile-phase three-dimensional TiO2 hierarchical nanostructures.

Specifically engineered three-dimensional (3D) and 1D morphologies are expected to play significant roles in the development of next-generation dye-sensitized solar cells. In this study, using a hydrothermal approach without a surfactant or template, we attempted to synthesize a 3D hierarchical rutile titanium dioxide (TiO2 ) architecture by varying the growth temperature and time. X-ray diffraction patterns of the synthesized TiO2 correlated well with rutile TiO2 . Scanning electron microscopy images exhibited different nanostructures, such as nanorods, aggregated nanorods, and 3D TiO2 microflowers comprised of nanorods at 100°C, 130°C, and 160°C, respectively, after growth for 6 h. A significantly improved efficiency was observed for the TiO2 microflowers. The TiO2 microflowers exhibited an efficiency of 1.16%, short-circuit current density of 12.8 mA cm-2 , open-circuit voltage of 0.692 V, and fill factor of 0.67.

High-efficiency of novel hierarchical 3D macroporous g-C3N4 material on solar-driven photocatalytic water-splitting for hydrogen evolution

The use of multi-pore nanostructured g-C3N4 photocatalysts is an efficient approach to separate photogenerated charge carriers and increase visible light photocatalytic performance. Recent progress has yielded nanostructured material through hard templating, which limits potential applications. Integrating the 2D building block into multidimensional porous structures remains a significant challenge in scalable production. Herein, a novel technique based on P407 bubble clusters templating and fixation by freezing is described for the first time to fabricate a 3D opened-up macroporous g-C3N4 nanostructures for photocatalytic H2 evolution. Three-dimensional hierarchical nanostructures provide more contact active sites and synergistically promote the creation of heterogeneous catalytic interfaces. This feature is very useful for understanding the transfer path of photoinduced charges as well as the origins of the high charge separation efficiency in photocatalytic reactions, thus yielding a remarkable visible light-induced H2 evolution rate of 4213.6 μmol h−1 g−1, which is nearly 5.6 times (716 μmol h−1 g−1) higher than that of lamellar bulk g-C3N4. This newly developed approach offers a promising alternative to synthesize broad-spectral response 3D hierarchal g-C3N4 nanostructures and can be extended to assemble other functional nanomaterials as building blocks into macroscopic configurations coupled with electronic modulation strategy simultaneously.

Adsorption sites and electron transfer characteristics of methyl orange on three-dimensional hierarchical flower-like nanostructures of Co-Al-layered double hydroxides: Experimental and DFT investigation

The dried layered double hydroxides (LDHs), have poor dispersibility, and are difficult to recycle in water. In this study, the cobalt-aluminum LDHs were prepared by hydrothermal reaction (BC@Co-Al-LDHs), and then further calcined to obtain hollow-structured BC@Co-Al-LDOs. The surface morphologies and physicochemical characteristics of these two materials were characterized. Simultaneously, batch tests were conducted to study their adsorption performances for methyl orange (MO). The maximum removal rate (90.24 %) and adsorption capacity (147.68 mg/g) of BC@Co-Al-LDOs for MO were 37.11 % and 60.72 mg/L higher than those of BC@Co-Al-LDHs, respectively. Based on the fitting results of the adsorption kinetic model, the type of MO adsorption by the two materials was chemisorption. Furthermore, density functional theory (DFT) was used to further study the adsorption mechanism of MO on the surface of these materials at the molecular level. The theoretical calculation results demonstrated that the SO3− in the MO was more prone to electrophilic reactions and accepted electrons from BC@Co-Al-LDHs, simultaneously, the Co adsorption site had the most accessible adsorption energy (−5.342 eV) contributing to the vertical adsorption. In addition, the partial density of states (PDOS) measurement revealed that MO interacted with the BC@Co-Al-LDHs essentially through s and p orbital hybridization.

Singlet oxygen-dominated activation of peroxymonosulfate by 3D hierarchical MnO2 nanostructures for degradation of organic pollutants in water: Surface defect and catalytic mechanism

Manganese dioxide (MnO2) is attracting significant attention in the activation of persulfate for the degradation of organic pollutants in water. But the factor determining the catalytic efficiency of MnO2, and the evolution of reactive oxygen species (ROS) remain equivocal and elusive. Herein, three-dimensional (3D) hierarchical MnO2 nanostructures are synthesized via the calcination of hydrothermal product and used to active peroxymonosulfate (PMS) for degradation of acid orange 7 (AO7) in water. The results show that the calcination temperature can tune the morphology of 3D hierarchical MnO2 nanostructures from flower to urchin-like as well as phase transformation from δ-MnO2 to α-MnO2. Owing to the presence of more surface defects and surface adsorbed oxygen species, the urchin-like α-MnO2 nanostructures prepared at 500 °C (MnO2-500) deliver the best catalytic activity in activation of PMS, and 98.3 % of AO7 is degraded in 300 s. Additionally, the MnO2-500 shows wide pH applicability (3.5–9.6). Quenching tests and electron paramagnetic resonance spectra reveal that the catalytic oxidation of AO7 in the MnO2-500/PMS system is mainly mediated by the non-radical pathway, and the dominated ROS is 1O2. Besides, electrochemical experiment confirms the presence of electron transfer in the catalytic process. Density functional theory calculations indicate that the CN and CS groups of AO7 with high electron density are easily attacked by electrophilic ROS, which is further confirmed by liquid chromatography-mass spectrometry. Finally, MnO2-500 exhibits gradually enhanced catalytic activity with the increased cycle number due to the increased surface defects and the surface adsorbed oxygen. This study provides new insight into the PMS activation by MnO2-based catalyst for the remediation of organic pollutants in water.

Pseudomorphic Replacement in the Transformation between Metal–Organic Frameworks toward Three-Dimensional Hierarchical Nanostructures

The construction of three-dimensional hierarchical materials from nano building blocks has received tremendous attention because of the intriguing architecture and promising application potential of these materials. However, the use of traditional assembly methods to construct hierarchical nanostructures with complicated 3D shapes across multiple length scales remains challenging. Herein, we developed a new strategy to fabricate hierarchical nanostructures by borrowing the concept of pseudomorphic replacement from mineralogy; this concept refers to a specific conversion between minerals with the preservation of the pristine shape through an interface-coupled dissolution–precipitation mechanism. By employing pseudomorphic replacement to the transformation between metal–organic frameworks (MOFs), a series of hierarchical MOF materials with similar nanostructures but various shapes and dimensions were successfully fabricated. The experiments verified that these transformations not only preserve the shape of the pristine MOF crystals but also proceed via an interface-coupled dissolution–recrystallization process. To our knowledge, our investigation is the first explicit demonstration of pseudomorphic replacement in the transformation between MOFs, offering a new route to hierarchical materials with enhanced control ability and extended control scope.

High magnetic field-engineered high mass loading sulfides with well-ordered hierarchical nanostructures for all-solid-state supercapacitors

Low energy density is becoming the largest sore point of supercapacitors. Constructing all-solid-state asymmetric supercapacitors (AASCs) with high mass loading and high utilization of electrochemically active materials can largely remedy the drawback. Herein, well-ordered hierarchical porous NiCo2S4 pine needles on carbon cloth (CC) with a loading mass as high as 10.76 mg cm−2 (NCS-12 T) were fabricated by low-temperature topotactic vulcanization of the high-mass-loading (Ni, Co)(CO3)0.5(OH)·0·.11H2O precursor (NCCH-12 T) yielded under 12 T high magnetic field (HMF). The loading mass on each CC tends towards equivalence and increases remarkably with the rise of HMF by guaranteeing sufficient ion supply. Impressively, a high overall capacitance of 10.46F cm−2 at 5 mA cm−2 was achieved without sacrificing the specific capacitance and rate capability that are slightly superior to those of the low mass loading NiCo2S4 electrodes instead. The striking electrochemical performances are ascribed to the available ion and electron transport in the whole electrode, which results from the construction of three-dimensional hierarchical porous nanostructures and HMF-derived well-ordered and uniform deposition via boosting ion transport. Finally, the NCS-12 T-based AASCs with high mass loading exhibit a high energy density of 280 μWh cm−2 at the power density of 1.71 mW cm−2, exceeding most state-of-the-art supercapacitors.

SnSe/Cu<sub>2</sub>SnSe<sub>3</sub> Heterojunction Structure with High Initial Coulombic Efficiency for Lithium-Ion Battery Anodes

Due to high theoretical specific capacity and abundant reserves, tin selenide-based materials have received tremendous attentions in the fields of lithium-ion batteries. Nevertheless, the huge volume changes during insertion/de-intercalation processes deteriorate the Coulombic Efficiency greatly. In order to solve it, the researchers have made great efforts by means of controlling nanoparticles granularity, carbon coating, ion doping et al. In this study, SnSe/Cu2SnSe3 heterojunction nanocomposites were synthesized by solvo-thermal method. The resulting SnSe/Cu2SnSe3 is a three-dimensional flower-like hierarchical nanostructure composed of nanoscale thin lamellae of a thickness of 8-12 nm. The unique nanostructure could shorten the diffusion path of lithium ions and expedite charge transfer, and therefore enhance the reaction kinetics. Compared with SnSe, the initial Coulombic efficiency of SnSe/Cu2SnSe3 is raised from 59% to 90% as the anode material of lithium-ion batteries.

CNT supported NiO hierarchal nanostructure on stainless steel substrate for efficient field emitters

The field emission application has recently focused on assembling nanoscale building blocks into three-dimensional (3D) hierarchical or hybrid nanostructure. The hierarchical nanostructure provides better field emission than a single nanostructure. In the present study, the chemical vapor deposition (CVD) method was used to synthesize 1D carbon nanotube (CNT) on stainless steel (SS) substrate. Nickel (Ni) was then sputtered on the synthesized CNT, and the sputtered substrate was treated hydrothermally in LiOH solution. The deposited Ni on CNT forms Ni(OH)2, and after oxidation, it was converted to NiO nanostructure. The structure, morphology, and chemical state of the samples were characterized by XRD, FESEM, Raman spectroscopy, and XPS. The SS-CNT exhibited a turn-on field and maximum emission current of 5.5 V/μm and 275 µA/cm2, respectively. However, SS-CNT-Ni demonstrated reduced field emission responses with turn-on field and maximum current 8.7 V/μm and 68 µA/cm2, respectively. The field emission response has been enhanced in the case of the SS-CNT-NiO sample as compared to the other structures. The turn-on field and maximum current densities were 5.1 V/µm and 719 µA/cm2 for the SS-CNT-NiO, respectively.

Adsorption Sites and Electron Transfer Characteristics of Methyl Orange on Three-Dimensional Hierarchical Flower-Like Nanostructures of Co-Al-Layered Double Hydroxides: Experimental and Dft Investigation

Adsorption Sites and Electron Transfer Characteristics of Methyl Orange on Three-Dimensional Hierarchical Flower-Like Nanostructures of Co-Al-Layered Double Hydroxides: Experimental and Dft Investigation

Fabrication and optical dispersions of three-dimensional hierarchical plasmonic nanostructures

This paper describes a facile method for the design and fabrication of hierarchical nanopatterns via aluminum anodization with an application for creating plasmonic crystals. Fabrication of highly-ordered anodized aluminum oxide nanopores requires an applied electric potential for anodization, which is typically set to match the pitch of nanoindentations on Al. This study reports a new voltage regime for Al anodization conditions where the process yields satellite pores of various shapes, periodicities, and sizes around the main pores. These new nanopatterned platforms provide an easy route to fabricate hierarchical metal nanostructures whose energy dispersions are shaped by the mode superposition of the surface plasmon polaritons originating from multiple periodic lattices.

Rational design of hierarchically sulfide and MXene-reinforced porous carbon nanofibers as advanced electrode for high energy density flexible supercapacitors

In this study, in-situ carbon coating technology was used to embed the sulfide-loaded MXene in the carbon nanofibers through electrospinning to improve the sulfide conductivity and ion transfer rate. Polyacrylonitrile (PAN) with a high carbon conversion rate was used as carbon nanofiber, while polyvinylpyrrolidone (PVP) with a low carbon conversion rate was used as a pore-forming sacrificial agent . PAN–PVP-based porous carbon nanofibers (PCNF) with good meso/macropore structure were prepared via a thermally induced phase separation process. FeCo 2 S 4 nanoparticles and ultra-thin Ti 3 C 2 T x MXene were uniformly fixed in PCNF in situ, and a flexible hybrid film was prepared as the electrode material of supercapacitors (FeCo 2 S 4 /MXene/PCNF). The FeCo 2 S 4 /MXene/PCNF hybrid membrane inherits a three-dimensional pore structure and hierarchical PCNF nanostructure . It can provide continuous channels for the rapid electrolyte diffusion, thereby obtaining electrochemically active FeCo 2 S 4 nanoparticles. Moreover, carbon nanofibers can act as a conductive core for providing effective electron transport for the rapid Faraday redox reaction of the FeCo 2 S 4 sheath or as a buffer matrix for reducing local volume expansion/contraction during long-term cycling. Therefore, the optimized FeCo 2 S 4 /MXene/PCNF hybrid membrane has excellent cyclic stability, which fundamentally solves the problems of poor sulfide conductivity and cyclic stability.

Three-Dimensional Hierarchical Core/shell Electrodes Using Highly Conformal TiO2 and Co3O4 Thin Films for High-Performance Supercapattery Devices.

The rational design and development of novel electrode materials with promising nanostructures is an effective technique to improve their supercapacitive performance. This work presents high-performance core/shell electrodes based on three-dimensional hierarchical nanostructures coated with conformal thin transition-metal oxide layers using atomic layer deposition (ALD). This effective interface engineering creates disorder in the electronic structure and coordination environment at the interface of the heteronanostructure, which provides many more reaction sites and rapid ion diffusion. At 3 A g-1, the positive CuCo2O4/Ni4Mo/MoO2@ALD-Co3O4 electrode introduced here exhibits a specific capacity of 1029.1 C g-1, and the fabricated negative Fe3O4@ALD-TiO2 electrode significantly outperforms conventional carbon-based electrodes, with a maximum specific capacity of 372.6 C g-1. The supercapattery cell assembled from these two interface- and surface-tailored electrodes exhibits a very high energy density of 110.4 W h kg-1 with exceptional capacity retention over 20,000 cycles, demonstrating the immense potential of ALD for the next generation of supercapacitors.

Hydrothermal Synthesis and Microwave Absorption Properties of Nickel Ferrite/Multiwalled Carbon Nanotubes Composites

It is well accepted that the microwave absorption performance of ferrite can be enhanced via the hybridization. However, it is still very challenging to design the hierarchical nanostructure of ferrite hybrids to fabricate wave absorbing composites with both the high efficiency and lightweight. Herein, we successfully realize the in-situ synthesis of nickel ferrite/multiwalled carbon nanotubes (NiFe2O4/MWCNTs) hybrids with a large-scale production by the hydrothermal method. The structural characteristics, morphology, electromagnetic and microwave absorption properties were analyzed by X-ray diffraction, scanning electron microscope and vector network analyzer. The morphological study shows that NiFe2O4 nanoparticles with a small size (tens of nanometers) are coated on the MWCNTs, leading to a three-dimensional hierarchical nanostructure. The NiFe2O4/MWCNTs hybrids show satisfied microwave absorption properties. Typically, the optimized sample shows the minimum reflection loss of −19 dB at 11.3 GHz, and the bandwidth of the reflectivity below −10 dB is 2.5 GHz with a thin thickness of 1.5 mm. This result shall be due to the improved dielectric losses or interface polarization etc. Our results demonstrate a facile approach for the design of ferrite-based microwave absorber to meet the requirements of lightweight, thin-thickness and high efficiency.

Rational fabrication of a g-C3N4/NiO hierarchical nanocomposite with a large surface area for the effective detection of NO2 gas at room temperature

High-performance and cost-effective NO2-based gas sensors of metal oxides that operate at room temperature (RT) are of immense importance. A design strategy of a three-dimensional hierarchical nanostructure formed by the combination of two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets that are decorated with nickel oxide (NiO) nanosheets (NSs) via a facile hydrothermal method has been investigated here. The as-fabricated nanocomposite (g-C3N4/NiO, NiCN) sensor showed high sensing performance toward NO2 gas with a maximal sensitivity of 25.4 to 50 ppm, fast response time (0.53 s) and quick recovery time (25.06 s). Furthermore, the optimized nanocomposite structure (NiCN-2) showed long-term stability (12 weeks), a low detection limit (10 ppb) and higher selectivity toward NO2 gas at RT. This exceptional sensing performance of the NiCN-2 sensor toward NO2 might be attributed to the unique 3D hierarchical structures with a large specific surface area (146.8 m2·g−1), highly porous surface, abundant defect sites, extended internal charge transfer between the p-n heterojunction and high adsorption and transportation rates in the nanocomposite sensor. This study provides a new strategy for the formation of heterostructures between metal oxides and g-C3N4 for excellent gas sensitivity and addresses the fabrication of highly potent gas sensors.

Pyrolysis-Derived Carbon Auto-Coated Co–Ni Oxide-based Nanoparticles on Graphene-like Nanosheets for High-Performance Oxygen Electrocatalysis

Engineering transition-metal-based bifunctional oxygen electrocatalysts with high activity and stability has always been a problem. Traditional bare transition-metal-based nanoparticles supported on the outer surface of carbon materials are susceptible to the Ostwald-ripening effect in a catalytic process, consequently suffering from poor long-term operation. However, constructing a highly efficient and stable bifunctional oxygen electrocatalyst is still challenging. Here, we report graphene-like carbon nanosheets modified with carbon shell-coated binary Co–Ni oxide-based nanoparticles (CoNiOx@C/G-NSs) by one-step pyrolysis method, in which the hybrids show a three-dimensional fluffy and hierarchical porous nanostructure and large numbers of carbon shell-coated binary Co–Ni oxide-based nanoparticles (CoNiOx@C) dispersed on graphene-like carbon nanosheets evenly. More excitingly, the carbon nanosheets are nitrogen-doped. When applied for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), the onset potential (Eonset) of OER reached 1.26 V, and onset potential of ORR and half-wave potential (E1/2) reached 0.90 and 0.78 V, respectively. The hybrids showed enhanced methanol tolerance, with few changes in the ORR performance with or without adding methanol, and high stability, with 84% activity retention after 10 h continuous reaction. The productivity of H2O2 is about 5% and the number of electron transfer (n) is about 3.9 in the process of catalyzing ORR; density functional theory calculation reveals its high selectivity in the 4e– pathway. Its excellent performance is mainly attributed to the synergistic enhancement effect: three-dimensional fluffy and hierarchical porous nanostructure provided a large catalytic activity area, which enabled the effective participation of species and facilitated rapid mass transfer; the rapid adsorption of O2 by N-doped graphene-like carbon nanosheets ensured fast electron transport; synergistic reactivity between carbon shell and CoNiOx enhanced the activity, and numerous CoNiOx@C nanoparticles reconciled the electron density of the carbon shell, which introduced more active sites; and the carbon shell weakened the Ostwald-ripening effect and ensured the stability of the nanoparticle. All advantages synergistically enhance the catalytic efficiency and make it one of the best bifunctional oxygen electrocatalysts.

Hierarchical Cu2S hollow nanowire arrays for highly efficient hydrogen evolution reaction

A self-supported three-dimensional unique hierarchical Cu2S hollow nanowire array nanostructure with excellent activity for the hydrogen-evolution reaction was synthesized in a facile and economical way.