NiO Hollow Microspheres Research Articles

High-performance trimethylamine gas sensor based on Sn-W co-doped MOF-derived hollow flower-like nickel oxide

In this study, a simple hydrothermal method was used to synthesize metal-organic framework-derived Sn/W co-doped NiO hollow flower-like spherical structure. The prepared NiO composites were utilized to prepare gas sensors to explore the response characteristics to different gases. The results showed that the response of the bimetal-doped NiO hollow microspheres to trimethylamine was 95 at 100 ppm, which was 63 times that of the pristine NiO nanoflowers. In addition, the sensor has a ppb-level detection limit for trimethylamine (0.1 ppm, 1.5). These good sensing performance of the Sn/W co-doped NiO sensor are not only affected by the initial resistance(Ra), but are also closely related to the rich oxygen vacancies, special hollow flower-like spherical structure and high Ni3+/Ni2+ ratio in the composite nanomaterials. This study provides an elegant co-doping method to improve the gas sensing performance of P-type MOS.

C12-2-C12mim][Br2]-assisted hydrothermal synthesis of hollow NiO microspheres for near-room temperature measurement of H2S

Hollow NiO microspheres were prepared using one-step hydrothermal method assisted by geminal dicationic ionic liquid (DIL) 1, 2-bis (N-dodecylimidazolyl) ethane bromide ([C12-2-C12mim][Br2]). The structures of the prepared microspheres can be controlled by adjusting the concentration of ionic liquid and reaction temperature. Furthermore, the amount of ionic liquid residue in these microspheres can also be controlled by changing the calcination temperature. Among them, the NiO hollow microspheres prepared by calcining the precursor at 600 °C (Ni1–600) in air display the most excellent gas sensing performance, including high response (35.6–100 ppm H2S) and low working temperature (50 °C). The excellent gas sensing performance of the Ni1–600 is attributed to the ionic liquid residue with appropriate content, which enhances the interaction between the analyte and the sensing material. The strong interaction effectively increases the sensitivity and reduces the working temperature of the sensor. The NiO hollow microspheres are expected to be a promising candidate material for the highly sensitive H2S gas sensor at near room temperature.

Self-templating hydrothermal synthesis of carbon-confined double-shelled Ni/NiO hollow microspheres for diphenylamine detection in fruit samples

Toxic substances, such as heavy metals, toxins, pesticides, pathogens, and veterinary drug residues in food are hazardous to consumer health. The variety and quantity of food consumption have increased owing to developments in the agricultural and food industries. Food safety has a substantial socioeconomic impact, and an increasing number of consumers have become aware of its importance. Therefore, simple and cost-effective analytical methods are required to quantify the safety of preservatives. Herein, we report an electrochemical method using double-shelled carbon-confined Ni/NiO (C@Ni/NiO) hollow microspheres to detect diphenylamine (DPA). The microspheres were synthesized by a self-templating hydrothermal method followed by calcination. The hydrothermal temperature and precursor ratio were optimized systematically to prepare double-shelled C@Ni/NiO hollow microspheres. The excellent electrocatalytic activity and electron transport properties of a C@Ni/NiO-modified glassy carbon electrode (GCE) were exploited in the electrochemical oxidation of DPA. Interestingly, the engineered C@Ni/NiO/GCE has a wide dynamic linear range (0.02–473 μM) and a DPA detection limit of 0.007 μM. In addition, the DPA sensor exhibited good selectivity, reproducibility, repeatability, and stability. The practical feasibility of the DPA sensor was evaluated in fruit samples (sweet tomatoes, apples, and red grapes), with considerable recovery.

Synthesis of hollow spherical nickel oxide and its gas-sensing properties

Semiconductor metal oxides have attracted wide attention in the area of gas sensor due to that they have unique advantages in the rapid and accurate detection of harmful gases. A simple strategy is to synthesize porous NiO hollow microspheres via a simple hydrothermal method with trisodium citrate as structure guide agent is presented in this paper, and the shell of the microsphere is composed of porous and lamellar assembly units. The cavity proportion can be adjusted by changing the amount of trisodium citrate. A reasonable mechanism was proposed to explain the formation of porous NiO hollow microspheres. As a gas-sensing material, porous NiO hollow microspheres show excellent gas selectivity and rapid response recovery time for n-butyl alcohol gas. When the content of trisodium citrate was 0.10 g, the synthesized hollow sphere NiO had the highest response value (25.6) to 100 × 10–6 of n-butyl alcohol at 300 °C and the response and recovery times were only 68 and 10 s.

Multi-shelled NiO hollow microspheres as bifunctional materials for electrochromic smart window and non-enzymatic glucose sensor

A multi-shelled NiO hollow sphere was synthesized by a facile glucose-mediated hydrothermal route. The carbonaceous microsphere was utilized as a sacrificial template for the formation of multi-shells. All the shells were formed by a single pyrolysis step. The multi-shelled hollow sphere can provide enhanced active surface area and additional reactive sites, which facilitate faster ion intercalation and deintercalation, and play key roles in electrochromic devices and sensing application, including glucose sensing. Herein, we employed the as-synthesized material for electrochromic devices. As expected, NiO multi-shelled hollow microspheres exhibit a superior transmission modulation (ΔT = 47%) and yield a coloration efficiency of ~ 85.3 cm2 C−1, which is ~ 2.37 times higher than that of NiO microflakes which was synthesized in the absence of glucose. The geometry of the self-supported multi-shelled architecture ensures that the active faradaic sites can be in intimate contact with the electrolyte to enhance ionic diffusion. The observed colored and bleached switching time of multi-shelled hollow sphere is 6.7 s and 2.7 s respectively. A quasi-solid-state electrochromic device is also displayed with the aid of gel electrolyte with reversible color change from dark brown to transparent. Furthermore, the multi-shelled NiO displayed excellent catalytic activity towards non-enzymatic glucose sensing with a high sensitivity of 1646 ± 5 μA cm−2 mM−1 over a linear range of 2 μM–2.6 mM with a lowest detection limit of 1.5 ± 0.2 μM. Analysis on blood serum as a real biological sample reflects the practicability of the fabricated sensor. Developing hollow structured multi-shelled materials based on metal oxides will pave the way to design advanced electrode materials for electrochromic smart windows and non-enzymatic glucose sensors.

3D Hierarchical N, O Co–Doped MoS2/NiO Hollow Microspheres as Reusable Catalyst for Nitrophenols Reduction

AbstractThe exploitation of efficient noble metal free catalyst for nitrophenols is of great importance. Herein, 3D hierarchical N, O‐MoS2/NiO hollow microspheres have been successfully prepared via a facile hydrothermal method. Characterizations reveal that the as‐obtained hollow microspheres were assembled by amorphous N, O co‐doped MoS2 and NiO nanosheets. Catalytic experiments show that the hollow microspheres displayed remarkably enhanced catalytic activity for 2, 3, 4‐nitrophenol reduction with the kapp reaching 1.72 min−1 for 4‐nitrophenol, among the best reported non‐noble metal catalysts. The greatly enhanced catalytic activity is attributed to the synergistic effects of abundant exposed catalytic edge sites, intimate P−N heterojunction between NiO and N, O‐MoS2, as well as the hollow porous structure. Moreover, the recovered N, O‐MoS2/NiO hollow microspheres can be reused in successive 8 cycles without much losing its activity. These results suggest that the novel N, O‐MoS2/NiO hollow microspheres had significant application potential for wastewater treatment.

Porous NiO/ZnO flower-like heterostructures consisting of interlaced nanosheet/particle framework for enhanced photodegradation of tetracycline

Various NiO/ZnO heterostructures have been prepared by a facile solvothermal method combined with subsequent calcination process. By adjusting the adding proportion of Ni/Zn, the superior performance in photocatalytic degradation of tetracycline (TC) can be achieved in porous NiO/ZnO flower-like microstructures consisting of interlaced nanosheet/particle framework. Compared with NiO hollow microspheres, flower-like NiO/ZnO samples exhibit the enhanced photocatalytic performance with high efficiency of 92% within 30 min as well as good photocatalytic cycle stability to TC, which is mainly ascribed to the combination of larger specific surface area (162.1 m2/g), unique surface/interface effect, faster electron/hole separation, and higher electron transmission. This work paves the way for other oxide composites applied as novel photocatalysts based on the design and construction of interlaced nanosheet/particle heterostructures.

Porous multishelled NiO hollow microspheres encapsulated within three-dimensional graphene as flexible free-standing electrodes for high-performance supercapacitors.

Exploration of electrode materials with well-defined nanostructures and good flexibility is an efficient approach for achieving high-performance and flexible energy storage systems. However, it is still challenging to well integrate active materials into flexible electrodes and simultaneously maintain satisfactory electrochemical performance. Herein, we successfully synthesize novel three-dimensional graphene (3DG)-encapsulated porous multishelled NiO hollow microsphere (3DG/pMS-NiO) composite aerogels via a modified self-templating method and a dopamine (DA)-assisted self-assembly route. The well-designed highly interconnected porous 3DG network and the close contact NiO-graphene structure of the 3DG/pMS-NiO composite aerogels offer multiple advantages such as high porosity and accessible area, improved conductivity, enhanced electrolyte diffusion and a simple electrode preparation process. Thus, the as-prepared flexible 3DG/pMS-NiO electrodes showed significantly improved specific capacitance of 710.4 F g-1 at 0.5 A g-1 and excellent rate capability with an ultrahigh capacitance retention of 92.5% at 10 A g-1. In addition, the fabricated asymmetric supercapacitors (3DG/pMS-NiO//AC) showed a high specific capacitance of 34.4 F g-1 at 1 A g-1 with a voltage window of 0-1.6 V, a large energy density of 12.3 W h kg-1 at a power density of 815.3 W kg-1, and a decent cycling stability. This work profoundly enlightens the material design and electrode preparation, and even opens up an avenue for the development of high-performance and flexible energy storage systems.

Zinc‐Doped Nickel Oxide Hollow Microspheres – Preparation Hydrothermal Synthesis and Electrochemical Properties

By using NiSO4·6H2O and Zn(NO3)2 as raw materials, zinc‐doped nickel oxide hollow microspheres (Zn‐NiO‐HM) were prepared through a hydrothermal method. Scanning electron microscope (SEM), transmission electron microscope (TEM), X‐ray photoelectron spectra (XPS), cyclic voltammetry (CV), galvanostatic current charge–discharge (GCD) and electro‐chemical impedance spectroscopy (EIS) were used to characterize the structure and the electrochemical properties of the Zn‐NiO‐HM. The results show that the Zn‐NiO‐HM had an obvious hollow microsphere structure, regular morphology and uniform particle size. The results of XPS indicate zinc was doped in the nickel oxide and existed in the form of Zn2+. The electrochemical measurements show that the electrochemical properties of the Zn‐NiO‐HM were better than those of the NiO powders and of the NiO hollow microspheres.

NiO hollow microspheres as efficient bifunctional electrocatalysts for Overall Water-Splitting

Development of efficient, earth-abundant and low-cost electrocatalyst for effective water electrolysis is highly demanding for production of sustainable hydrogen energy. In this paper, we report the cost-effective synthetic protocol for porous NiO hollow spheres in large scale through a simple spray drying strategy, using aqueous nickel ammonium carbonate complex solution, followed by calcination. The synthesized NiO hollow spheres calcined at 300 °C (NiO-300) are porous, made of nanoparticles in size range of 10–16 nm with a size range of 2.5–4 μm and total surface area of 120 m2/g. The NiO-300 exhibited excellent bifunctional electrocatalytic water splitting characteristic, both OER, and HER, in basic solution. NiO-300 modified glassy carbon electrode showed superior water electrolysis kinetics and to achieve 10 mA cm−2 current density, it required 370 mV overpotential for OER and 424 mV overpotential for HER in 1 M KOH. It is also worked well with cost-effective plastic chip electrode. An assembled two-electrode system by pairing NiO modified plastic chip electrode as both anode and cathode in a 1.0 M KOH electrolyte for overall water splitting exhibit clear bubble formation at 1.6 V potential.

Bio-template synthesized NiO/C hollow microspheres with enhanced Li-ion battery electrochemical performance

NiO microspheres with well-defined hollow structure were successfully obtained using spherical yeast as a natural bio-template. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The morphologically uniform NiO hollow microspheres prepared with yeast template after calcination had an averaged diameter of 1.5–2 μm and the shell thickness of ∼500 nm. The concentration of Ni(NO3)2, calcination temperature and aging time play important roles on the crystal phase and morphologies of the NiO hollow microspheres. Meanwhile, the NiO/C hollow microspheres were successfully fabricated via a simple hydrothermal method using glucose as carbon source. A possible formation mechanism of forming NiO/C hollow microspheres was proposed and the electrochemical performance of the NiO/C hollow microspheres as anode material for Li-ion batteries was investigated. Compared with the samples prepared without template or without carbon coating, the as-prepared NiO/C hollow microspheres show higher discharge capacity and better cycle performance as an anode material in Li-ion batteries.

Facile synthesis of nanocrystalline-assembled nest-like NiO hollow microspheres with superior lithium storage performance

Interconnected nest-like NiO hollow microspheres assembled from nanocrystallites are prepared by a facile hydrothermal method followed by annealing at 700 °C in air.

Highly controlled synthesis of multi-shelled NiO hollow microspheres for enhanced lithium storage properties

Nickel oxide microspheres with porous multi-shelled structure were synthesized via a sequential templating approach using carbonaceous microspheres (CMSs) as sacrificial agent. When applied as anode material for lithium ion batteries, the as-prepared porous triple-shelled NiO hollow spheres show excellent cycling performance and outstanding high-rate capability, as well as high specific capacity. During all the 100 discharge-charge cycles under a current density of 500mA/g, the porous triple-shelled NiO hollow spheres can stably deliver a reversible capacity of ca. 789mAh/g. Even at a high current density of 2000mA/g, the specific discharge capacity of the porous triple-shelled NiO hollow spheres is still as high as 721mAh/g, which is twice larger than that of commercial graphite. The superior electrochemical performance can be attributed to the porous multi-shelled hollow microstructure which guarantees more lithium-storage sites, a shorter lithium-ion diffusion length, and sufficient void space to buffer the volume expansion.

Multishelled NiO Hollow Microspheres for High-performance Supercapacitors with Ultrahigh Energy Density and Robust Cycle Life.

Multishelled NiO hollow microspheres for high-performance supercapacitors have been prepared and the formation mechanism has been investigated. By using resin microspheres to absorb Ni2+ and subsequent proper calcinations, the shell numbers, shell spacing and exterior shell structure were facilely controlled via varying synthetic parameters. Particularly, the exterior shell structure that accurately associated with the ion transfer is finely controlled by forming a single shell or closed exterior double-shells. Among multishelled NiO hollow microspheres, the triple-shelled NiO with an outer single-shelled microspheres show a remarkable capacity of 1280 F g−1 at 1 A g−1, and still keep a high value of 704 F g−1 even at 20 A g−1. The outstanding performances are attributed to its fast ion/electron transfer, high specific surface area and large shell space. The specific capacitance gradually increases to 108% of its initial value after 2500 cycles, demonstrating its high stability. Importantly, the 3S-NiO-HMS//RGO@Fe3O4 asymmetric supercapacitor shows an ultrahigh energy density of 51.0 Wh kg−1 at a power density of 800 W kg−1, and 78.8% capacitance retention after 10,000 cycles. Furthermore, multishelled NiO can be transferred into multishelled Ni microspheres with high-efficient H2 generation rate of 598.5 mL H2 min−1 g−1Ni for catalytic hydrolysis of NH3BH3 (AB).

NiO hollow microspheres interconnected by carbon nanotubes as an anode for lithium ion batteries

In this work, NiO hollow microspheres interconnected by multi-walled carbon nanotubes (MWCNTs) were prepared, characterized, and evaluated in terms of lithium ion storage properties. Characterization results showed that the NiO hollow microspheres were formed by self assembly of NiO nanoparticles promoted by MWCNTs, which connected the NiO microspheres to form a long-range network. Electrochemical measurement results showed a charge capacity as high as 597.2mAhg−1 when cycling at the rate 2C and maintained 85.3% capacity of 0.1C. After cycling for 100 times at 1C, it maintained a capacity of 692.3mAhg−1 with retention 89.3% of the initial capacity. The observed excellent electrochemical performance is attributed to the presence of MWCNTs interconnecting the NiO microspheres of the composite material, of which electronic conductivity was improved, and the mesoporous hollow structure effectively alleviated the volume changes to maintain the structural stability during cycling.

Hierarchical flower-like NiO hollow microspheres for non-enzymatic glucose sensors

Abstract Hierarchical flower-like NiO hollow microspheres were controllably prepared by a facile hydrothermal method using carbon spheres as the template. Their structure and properties for non-enzymatic glucose sensors were investigated. The results showed that the hierarchical flower-like NiO hollow microspheres are composed of the interconnecting porous NiO nanoplates and each nanoplate is assembled by NiO nanoparticles with the length of about 12.5 nm and the width of about 10 nm. Furthermore, the hierarchical flower-like NiO hollow microspheres obtained at different temperatures were analyzed with the electro-catalytic activity toward the oxidation of glucose in alkaline solution, and the glucose sensor with hierarchical flower-like NiO hollow microspheres obtained at 550 °C exhibits the best performance with the linear range of 5 μM–364 μM and sensitivity of 288.87 mA mM− 1 cm− 2. The sensor is also used for detection of glucose with a relative concentration ranging from 2.96 mM to 7.46 mM and sensitivity of 37.82 mA mM− 1 cm− 2. More importantly, long-term stability and favorable anti-interference were obtained as a result of the hierarchical hollow structure.

Synthesis and electrochemical investigation of hollow hierarchical metal oxide microspheres for high performance lithium-ion batteries

In this paper, a versatile facile route to synthesize mesoporous hollow-structured metal oxides is demonstrated using sulfonated polystyrene (SPS) microspheres as hard templates. SEM and TEM images show that the Fe2O3, Co3O4 and NiO hollow microspheres are self-assembled by nanorods, nanoparticles and nanosheets, respectively. Hollow and mesoporous structures not only provide enhanced mechanical stabilities to buffer the large volume changes during the charge/discharge processes, but also provide large specific areas for sufficient penetration of electrolyte, thus leading to an excellent cyclic stability and rate capability. As proofs-of-concepts, all of the hollow and mesoporous metal oxides (Fe2O3, Co3O4 and NiO) deliver high initial discharge capacities and good capacity retentions (>80%) after more than 100 cycles in half cells. Most important of all, these assembled full-cells (MxOy(M=Fe, Co, Ni)/LiCoO2) also delivere excellent electrochemical performances. This work clearly demonstrates that the MxOy(M=Fe, Co, Ni)/LiCoO2 configuration are promising alternative high power-density energy storage devices in the near future.

NiO nanosheets assembled into hollow microspheres for highly sensitive and fast-responding VOC sensors

NiO hollow microspheres synthesized through a SiO2 spheres template-assisted approach show a very good gas response towards volatile organic compound vapors.

Facile synthesis of porous NiO hollow microspheres and its electrochemical lithium-storage performance

Novel porous NiO hollow microspheres are fabricated by a facile two-step method involving the ultrasound-assisted synthesis of nickel oxalate precursors and subsequent thermal annealing in air. The as-prepared NiO microspheres are composed of loosely packed nanoparticles with diameters around 30–80nm, and have a main pore distribution from 3 to 20nm with a mean pore size of 5.7nm. When evaluated as anode material for lithium ion battery, the porous NiO hollow microspheres showed enhanced electrochemical performance with high lithium storage capacity, satisfactory cyclability and rate capacity. The reversible capacity of the NiO microspheres retained 380mAhg−1 after 30 cycles at 200mAg−1. Even when cycled at various rate for more than 60 cycles, the capacity could recover to 520mAhg−1 for the current of 100mAg−1. The good lithium-storage performance can be attributed to the unique porous architecture, which provides the structural flexibility for volume change and the routes for fast Li+ diffusion.

L-cysteine-assisted preparation of porous NiO hollow microspheres with enhanced performance for lithium storage

Porous NiO hollow microspheres have been synthesized via a simple hydrothermal process using L-cysteine as a structure-directing agent followed by calcination. The as-synthesized NiO microspheres are hollow with diameters of 2–3 μm. The shells of the microspheres are built from nanoparticles with diameters of 30–50 nm, and the interior cavities are around 0.75 μm in diameter. A plausible mechanism has been proposed to explain the formation of the porous NiO hollow spheres. When evaluated as anode materials for lithium ion batteries, the porous NiO hollow microspheres show outstanding electrochemical performances, including high reversible capacity of 847.2 mAh g−1 after 50 cycles at 100 mA g–1, high rate capability with a discharge capacity of 470 mAh g−1 at a current density of 800 mA g−1, and good cycling stability. The excellent lithium-storage performance can be attributed to the porous hollow architectures, which provide fast ion/electron transfer and the structural flexibility for volume change during the cycling process.