NiO Hollow Spheres Research Articles

Preparation and Electrochemical Investigation of NiO Hollow Sphere from Bio Waste (Sugarcane Bagasse) Extract for Energy Storage Applications

Preparation and Electrochemical Investigation of NiO Hollow Sphere from Bio Waste (Sugarcane Bagasse) Extract for Energy Storage Applications

Dual Atoms (Fe, F) Co-Doping Inducing Electronic Structure Modulation of NiO Hollow Flower-Spheres for Enhanced Oxygen Evolution/Sulfion Oxidation Reaction Performance.

Heteroatoms Fe, F co-doped NiO hollow spheres (Fe, F-NiO) are designed, which simultaneously integrate promoted thermodynamics by electronic structure modulation with boosted reaction kinetics by nano-architectonics. Benefiting from the electronic structure co-regulation of Ni sites by introducing Fe and F atoms in NiO , as the rate-determined step (RDS), the Gibbs free energy of OH* intermediates (ΔGOH* ) for Fe, F-NiO catalyst is significantly decreased to 1.87eV for oxygen evolution reaction (OER) compared with pristine NiO (2.23eV), which reduces the energy barrier and improves the reaction activity. Besides, densities of states (DOS) result verifies the bandgap of Fe, F-NiO(100) is significantly decreased compared with pristine NiO(100), which is beneficial to promote electrons transfer efficiency in electrochemical system. Profiting by the synergistic effect, the Fe, F-NiO hollow spheres only require the overpotential of 215mV for OER at 10mA cm-2 and extraordinary durability under alkaline condition. The assembled Fe, F-NiO||Fe-Ni2 P system only needs 1.51V to reach 10mA cm-2 , also exhibits outstanding electrocatalytic durability for continuous operation. More importantly, replacing the sluggish OER by advanced sulfion oxidation reaction (SOR) not only can realize the energy saving H2 production and toxic substances degradation, but also bring additional economic benefits.

Promoting the electrocatalytic activity through the introduction of oxygen vacancies to core–shell NiO hollow sphere catalysts for efficient oxygen evolution

The contribution of oxygen vacancies for improving the OER activity of NiO.

Highly Sensitive Ethanol Sensing Using NiO Hollow Spheres Synthesized via Hydrothermal Method

Excessive ethanol gas is a huge safety hazard, and people will experience extreme discomfort after inhalation, so efficient ethanol sensors are of great importance. This article reports on ethanol gas sensors that use NiO hollow spheres assembled from nanoparticles, nanoneedles, and nanosheets prepared by the hydrothermal method. All of the samples were characterized for performance evaluation. The sensors based on the NiO hollow spheres showed a good response to ethanol, and the hollow spheres assembled from nanosheets (NiO-S) obtained the best ethanol gas-sensing performance. NiO-S provided a larger response value (38.4) at 350 °C to 200 ppm ethanol, and it had good stability and reproducibility. The nanosheet structure and the fluffy surface of NiO-S obtained the largest specific surface area (55.20 m2/g), and this structure was beneficial for the sensor to adsorb more gas molecules in an ethanol atmosphere. In addition, the excellent sensing performance could ascribe to the larger Ni3+/Ni2+ of NiO-S, which achieved better electronic properties. Furthermore, in terms of commercial production, the template-free preparation of NiO-S eliminated one step, saving time and cost. Therefore, the sensors based on NiO-S will serve as candidates for ethanol sensing.

Automobile Cab Air Detection Based on Hollow Sphere NiO Gas Sensor

A novel NiO hollow sphere was synthesized by a simple water bath method while the carbon balls served as templates. Characterization and gas-sensing performance of NiO hollow spheres were tested. Owing to its hollow structure, the NiO obtained large specific surface area and abundant active sites. Furthermore, the gas sensors showed the enhanced formaldehyde sensing performance obtained a gas response of 21 to 50 ppm formaldehyde at 300 °C, short response/recovery time as 12 and 20 s, and excellent stability. These results indicate that the NiO hollow spheres play an important role on the VOCs sensing performance for practical detectors.

Fabrication of Multi‐Walled Carbon Nanotubes ‐ Wrapped Mesoporous NiO Hollow Spheres for Asymmetric Supercapacitors applications

AbstractMulti‐walled carbon nanotubes (MWCNTs) ‐ wrapped mesoporous NiO hollow spheres (MNHS) have been successfully synthesized via hydrothermal route using carbon spheres as templates. Structural, textural, morphological and electrochemical properties of MNHS were investigated. Galvanostatic Charge Discharge (GCD) analysis reveals the maximum specific capacity of 566 C g−1 at 1 A g−1.Furthermore,An Asymmetric supercapacitor (MNHS//RGO) has been fabricated and delivers the specific capacity of 75 C g−1 with an energy density of 121.17 W h kg−1 at the current density of 0.5 A g−1. The device shows excellent cyclic stability ie.,94 % of retention even after 3000 cycles.

High-frequency ultrasonic pyrolysis of 200 nm ultrafine Fe-doped NiO hollow spheres for efficient oxygen evolution catalysis

High-frequency ultrasonic pyrolysis (3 MHz) was developed to prepare ultrafine Fe-doped NiO porous hollow spheres ∼200 nm. The material showed a low overpotential of 288 mV for a current density of 10 mA cm−2 as oxygen evolution reaction catalyst.

Triple-shell NiO hollow sphere for p-type dye-sensitized solar cell with superior light harvesting

In this article, new p-DSSC electrodes are fabricated using NiO hollow spheres (HSs) prepared through a facial one-step hydrothermal process. The current-voltage (J-V) curve indicates that p-DSSCs fabricated using triple-shell NiO HS have excellent photoelectrochemical performance, with a photoelectrical efficiency of 1.79%. The UV–vis diffused reflectance spectra indicate that the triple-shell NiO HS, with its unique structure, has superior light reflection, scattering ability and large surface area with more inner cavities, which helps harvest more light. Electrochemical impedance spectroscopy (EIS) further confirms that triple-shell NiO HS shows fast dye regeneration, improved hole transport and suppressed recombination. The research work of unique NiO HS is important for the selection of efficient photocathode materials for p-DSSCs.

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.

Highly porous metal organic framework derived NiO hollow spheres and flowers for oxygen evolution reaction and supercapacitors

In this study, metal-organic-framework (MOF) derived porous NiO hollow spheres and flowers were obtained using facile solvothermal synthesis and heat treatment. After pyrolyzing, the flower like and hollow spherical like morphology of NiO nanoparticles was successfully inherited from the initial MOF-based templates. The electrochemical studies demonstrated that the porous NiO hallow spheres unveiled a better supercapacitive performance (specific capacitance (Cs) = 1058 F g−1 at current density (j) = 2 A g−1) and oxygen evolution reaction (OER) catalytic activity (overpotential (ɳ) = 323 mV) compared to porous NiO flowers (Cs = 857 F g−1 at j = 2 A g−1 and ɳ = 346 mV). Moreover, excellent capacity retention of over 93% was obtained in porous NiO-hs nanoparticles even after 5000 cycles. The fabricated NiO//Fe2O3 asymmetric supercapacitor delivered an energy density (E) of 35.75 W h Kg−1 under power density (P) of 780 W kg−1 and showed promising stability over 3000 cycles. Considering the ease of preparation and high catalytic activity and supercapacitive performance, these prous NiO hallow structures can be considered as a potential electrode material for next generation energy storage devices and OER catalysts.

Sandwich-like dual carbon layers coated NiO hollow spheres with superior lithium storage performances

Transition metal oxides (e.g. NiO) have been considered as promising high-capacity anode in lithium ion batteries (LIBs). However, the low electronic conductivity and huge volume change during cycling lead to rapid capacity fading and poor rate capability. To solve those drawbacks, we design a sandwich-like dual carbon layers coated hollow structured NiO (C@NiO@NC). The NiO nanosheets are anchored on the surface of hollow carbon nanospheres and then coated with N-doped porous carbon layer, which confine them between two carbon shells. Such hierarchical architecture with high surface area increases the contact between the electrode and electrolyte, resulting in decreased Li+ diffusion pathway. Moreover, the dual carbon layers enhance the electronic conductivity of C@NiO@NC and effectively buffer the volume changes of NiO during cycling. Therefore, this sample delivers a high capacity (1189 mA h g−1 at 100 mA g−1), superior rate capability (420 mA h g−1 at ultrahigh rate of 10000 mA g−1) and outstanding cycling stability (96.1% at 1000 mA g−1 after 1000 cycles) when used as LIBs anode. The density functional theoretical calculation further proves the enhanced electronic conductivity and more energetic favorable capability of C@NiO@NC. This facile method can be extended to other transition-metal oxides with superior electrochemical performance.

Decoration of NiO hollow spheres composed of stacked nanosheets with CeO2 nanoparticles: Enhancement effect of CeO2 for electrocatalytic methanol oxidation

High-performance and low-cost electrocatalysts for electrochemical methanol oxidation reaction (MOR) are essential for the wide application of direct methanol fuel cells (DMFC). Herein, CeO2–NiO composites with CeO2 nanoparticles homogeneously supported on the surface of NiO hollow spheres composed of stacked nanosheets are synthesized via a facile two-step route and tested as noble-metal-free electrocatalysts towards methanol oxidation in alkaline solution. Optimal loading of CeO2 nanoparticles with a uniform size of ∼8 nm greatly enhances the electrocatalytic activity and stability comparing with pristine NiO hollow spheres for MOR. It is proposed that a synergistic effect resulting from the proper loading content and high dispersion of CeO2 nanoparticles on the surface of NiO nanosheets boosted the formation of active NiOOH species, which enhanced the electrocatalytic activity and stability of CeO2–NiO catslysts for MOR. CeO2 nanoparticles exhibit good promotion effect as co-catalyst in electrocatalysis, and CeO2–NiO nanocomposites show potential as inexpensive anode catalysts for DMFC applications.

NiO@NiO and NiO@Co³O⁴ Hollow Core/Shell Composites for High-Performance Supercapacitor Electrodes.

In the present work, NiO@NiO and NiO@Co³O⁴ core/shell composites have been fabricated by a facile hydrothermal process and investigated as electrodes for supercapacitors. The structure and the morphology of as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicated that the NiO hollow spheres were decorated by NiO nanosheets and Co³O⁴ nanowires. Electrochemical properties were evaluated by cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy. According to the results NiO@NiO and NiO@Co³O⁴ core/shell composites exhibited high specific capacitance, being promising for high-performance supercapacitors.

Dual-mode gas sensor for ultrasensitive and highly selective detection of xylene and toluene using Nb-doped NiO hollow spheres

A single gas sensor with dual functionality for ultrasensitive and highly selective detection of p-xylene and toluene was designed using NiO hollow spheres doped with Nb. The pure and Nb-doped NiO hollow spheres were prepared by one-pot ultrasonic spray pyrolysis and subsequent heat treatment at 500 °C for 2 h. The Nb-doped NiO hollow spheres ([Nb]/[Ni] = 0.1) showed an ultrahigh response to 5 ppm of p-xylene (resistance ratio = 1752) and toluene (resistance ratio = 607), with negligible cross-responses to 5 ppm ethanol, benzene, carbon monoxide, and formaldehyde. In contrast, pure NiO hollow spheres showed negligibly low responses to 5 ppm of all analyte gases. In addition, the Nb-doped NiO hollow spheres exhibited dual sensing characteristics for selectively detecting p-xylene and toluene at 350 °C and 400 °C, respectively. The significant improvement of the response and selectivity for p-xylene and toluene can be explained by the high gas accessibility of hollow spheres, the Nb-doping-induced decrease in the charge carrier concentration, and the catalytic promotion of gas reforming reaction of less reactive xylene and toluene into more active species. The dual function of selectively detecting p-xylene and toluene in Nb-doped NiO hollow spheres is explained by the competition between oxidative filtering and gas reforming reaction depending on the operation temperature and sensing film thickness. The Nb-doped NiO hollow spheres can be used to design a single gas sensor with dual selectivity of xylene and toluene for reliable monitoring of the indoor air quality.

Non-Enzymatic Electrooxidation of Urea with a Disposable Paper-Based Sensor Using Hierarchical NiO Hollow Sphere

Urea in the urine, protein metabolism, is present in the final product of human. The level of urea is a crucial biomarker that can assess the metabolic activity of humans such as the liver and renal function. [1] A high level of urea in the urine can result in kidney failure, dehydration, and gastrointestinal bleeding, while a low level can lead to nephritic syndrome, hepatic failure, etc. [2] Therefore, accurate and rapid sensing of urea is essential in a diagnostic clinic. Recently, paper-based analytical devices (PAD) are gaining its popularity as a manageable device for point-of-care equipment due to its inexpensive, portable, disposable, and environmentally-friendly qualities.[3] The majority of electrochemical biosensors rely on enzymes, such as urease; yet, utilization of enzyme is limited due to its high cost, poor reproducibility, and most of all, thermal and chemical instability which can influence the duration of sensor that depends on storage conditions such as temperature, pH, and humidity.[4] In addition, non-enzymatic biosensors has been attracted with the advantage of simplicity, redox flexibility, stability, and low cost. As a non-enzymatic metal-based material, Ni-based nanomaterials exhibited excellent catalytic activity over urea originated from catalytic effect for the formation of the redox couple of Ni(II) and Ni(III) on the surface. [5] When compared to enzymatic-based sensors, non-enzymatic catalysts tend to present lower sensitivity and higher limit of detection corresponding to lower performances of urea biosensor. To address this limit, there have been efforts to modify nanostructures with various shapes such as nanofiber, nanoparticle, and nanoflake arrays. Here we investigated a hollow sphere structure with nanosheet building block by using a hydrothermal method. The hollow sphere structure can increase the selectivity and sensitivity for urea biosensor by providing facile transport channels through electrolyte that exploits its inner and outer surfaces as the active site with maintaining the structural stability of the catalyst. Integration of non-enzymatic hierarchical catalyst on disposable PAD will lead to a high potential for the development of point-of-care testing devices. In this study, a non-enzymatic electrochemical paper-based sensor using hollow structure NiO was developed and demonstrated for the determination of urea. PADs were fabricated by sputtering on cotton paper, and hollow NiO was synthesized by hydrothermal method. Structure and morphologies of hierarchical NiO on PAD were characterized by XRD and SEM. Electrochemical properties such as selectivity and LOD were conducted by using a potentiostat with urea solution. A detailed description of the fabrication process and discussion of structure formation and sensing performances of hollow nickel oxide catalyst will be presented.

The 3D crystal morphologies of NiO gas sensor and constantly improved sensing properties to ethanol

We successfully synthesized three kinds of NiO microspheres with solid, porous and hollow nanostructure via one-step hydrothermal method. The results indicated that the gas sensing performances of the porous sphere and hollow sphere are better than that of the solid sphere, which was attributed to the high specific surface area and the small size of Debye length. We find that the ethanol molecules can enter the interior of the NiO hollow sphere to have completed gas-sensing reactions because of enough response time, which lead to abundant effective gas diffusion and sufficient contact between with NiO, and it means more atoms can directly react with the gas to increase sensitivity. In this way, this article provides some suggestions and ideas for the development of gas sensor in the future.

Partly nitrogenized nickel oxide hollow spheres with multiple compositions for remarkable electrochemical performance

In order to improve the conductivity of NiO, a simple and effective strategy has been utilized. Here, we synthesized partly nitrogenized nickel oxide hollow spheres and used them as an electrode material of a supercapacitor. It was found that the prepared partly nitrogenized material possessed a mesoporous shell of multiple compositions consisting of NiO, Ni2O3, Ni3N, and N-doped NiO, the latter partly substituted with nitrogen. The first-principles calculations were also employed to investigate the composite structure and the result demonstrated an improved electronic conductivity. The partly nitrogenized NiO spheres acted as a battery-type electrode material delivering a gravimetric specific capacity of 492C g−1 at 1 A g−1 and a long-term stability in a three-electrode system. The assembled hybrid supercapacitor exhibited a maximum capacitance of 121F g−1 at 1 A g−1, a high energy density of 37.8 Wh kg−1 and power density of 37.5 kW kg−1, and high capacitance retention after 5000 charge–discharge cycles. The excellent electrochemical performance indicates that the partly nitrogenized NiO hollow spheres can compare favorably with nanostructured NiO materials composited with carbon nanotubes and reduced graphene oxide for application in energy storage devices.

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.

Label-free Kanamycin sensor development based on CuO[sbnd]NiO hollow-spheres: Food samples analyses

Kanamycin (KAN) is commonly used as an amino-glycoside antibiotic and enduring KAN in animal derivative food causes intensive adverse effects in human health. Here, at first copper oxide co-doped nickel oxide hollow-spheres (CuONiO HSs) were synthesized using a facile hydrothermal method (HTM) in an alkaline phase and then characterized by various conventional methods such as Fourier-transform infrared spectroscopy (FTIR), UV–visible spectroscopy (UV–vis.), Field Emission Scanning Electron Microscopy (FESEM), Energy-dispersive X-ray spectroscopy (XEDS), X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (XRD) to find out the nature of materials as binding energy, band-gap energy, morphology, crystallinity, functional groups, and elemental analyses. A selective and label-free KAN sensor was developed with the modification of slight coating of HSs onto a glassy carbon electrode (GCE) using nafion (Nf) coating binder at room conditions. Improved electrochemical performances of sensitivity, linear dynamic range (LDR), and long-term stability of selective KAN were achieved by reliable electrochemical technique. Based on signal to noise ratio 3, sensitivity and limit of detection (LOD) of sensor were calculated as 1.9 × 10−4 μAμM−1 cm−2 and 0.5 ± 0.02 nM respectively. The hydrothermally synthesized CuONiO HSs is significant advancement in fabricating with Nf/GCE decorated sensor probe in favor of enzyme-free detection of chemicals in biological system. In conclusion, the proposed sensors can be applied effectively for the selective and sensitive detection of KAN in food samples with satisfactory and acceptable results.

NiO hollow nanospheres with different surface by a bubble-template approach and its gas sensing

In this work, we report on the use of bubbles as a template, can adopt a slight hydrothermal method and subsequent calcination synthesized NiO hollow sphere successfully, and then control the reaction time and temperature conditions to form two different NiO surface. It was found that the fluffy structure with pores and the flower-like structure with nanometer plate. The results show that NiO with hollow sphere has excellent performance in gas sensing test and its special surface has high specific surface area, which has good response sensitivity to 400 ppm C2H5OH. So, it is a promising sensing material for detection of C2H5OH. In addition, based on the experimental results, we also proposed that the evolution mechanism about NiO hollow spheres and the gas sensitive mechanism on the surface of microspheres.