NiO ZnO Research Articles

Enhancing the Electrochemical Efficiency of ZnO/NiO Nano Composite Through Air Plasma Treatment

AbstractThis investigation examines the electrochemical behaviors of ZnO/NiO nanocomposites synthesized through a hydrothermal method and subsequently subjected to air plasma treatment, highlighting their potential in energy storage applications. XRD analysis confirmed the highly crystalline nature of the wurtzite ZnO and cubic NiO phases without secondary impurities. Plasma treatment enhanced crystallinity, as evidenced by sharper diffraction peaks. FTIR analysis revealed improvements in oxygenated functional groups posttreatment. FESEM images showed uniform spherical structures (∼2 µm) with increased surface roughness, and EDAX confirmed the elemental composition. Electrochemical analysis revealed significant improvements in performance due to plasma treatment. The plasma treated ZnO/NiO exhibited a total capacitance of 4773 F/g, compared to 2773 F/g for untreated samples. Specific capacitance at 10 mV/s decreased from 829 F/g (untreated) to 691 F/g (treated); however, at 100 mV/s, the treated sample retained a higher capacitance (331 F/g) than the untreated (187 F/g). A higher b‐value (0.742) for treated samples indicates the enhanced capacitive behavior. Charge‐discharge studies demonstrated high reversibility, with treated samples achieving better nonlinear double layer characteristics. Impedance spectroscopy showed reduced polarization and charge transfer resistance for treated samples compared to untreated, indicating improved conductivity and active site availability. These outcomes spotlight the effectiveness of the plasma treatment of ZnO/NiO nanocomposites.

Arrangement of n-type ZnO and p-type NiO nanofibrous thin films on FTO electrode for electrochemical impedance spectroscopy of glucose biosensors

Arrangement of n-type ZnO and p-type NiO nanofibrous thin films on FTO electrode for electrochemical impedance spectroscopy of glucose biosensors

The effect of annealing on the structural, optical, electrical and photoelectric properties of ZnO/NiO heterostructures

In this study, n-ZnO/p-NiO heterostructures on glass substrates with an indium tin oxide (ITO) covering were obtained by using the spray pyrolysis methodology. In order to act on the structural and local compositional defects, the samples were annealed under vacuum in the temperature range of Ta = (300 – 500)°C in steps of ΔT = 50°C. X-ray diffraction results indicate the presence of only the hexagonal ZnO and cubic NiO phases in the studied samples, which was confirmed by Raman spectroscopy. Low-temperature photoluminescence (PL), as well as absorption and photoconductivity, were studied to establish the optical properties, the nature of electronic optical transitions, the energy level position of the different defects present in the samples, and the effect of temperature annealing on these properties The band gap of the compounds was determined using the Tauc approximation and the first derivative of the absorption coefficient. Likewise, the current-voltage characteristics of the n-ZnO/p-NiO heterostructures and their diode character, were analyzed.

Biogenic fabrication of NiO-ZnO-CaO ternary nanocomposite using Azadirachta Indica (Neem) leaves extract with proficient photocatalytic degradation of rhodamine B dye

In the current study, a ternary nanocomposite (NiO–ZnO–CaO) was successfully synthesized through the co-precipitation method using Azadirachta Indica (neem) leaves extract as green approach. The characterization of prepared nanocomposite was conducted using FT-IR, XRD, SEM and EDS to determine the metal oxides absorption bands, structural properties, elemental composition, and surface morphology of the nanocomposite. FT-IR analysis revealed characteristic vibrational peaks at 621, 684, and 721 cm−1, corresponding to Ni-O, Zn-O, and Ca-O bond vibrations, respectively. XRD patterns showed distinct diffraction peaks, indicative of the hexagonal structure of ZnO and the cubic structures of NiO and CaO. EDS analysis confirmed the presence of calcium, nickel, zinc, and oxygen with weight percentages of 9.2%, 14.4%, 15.1%, and 20.9%, respectively. SEM images displayed an irregular cube like morphology with noticeable clustering within the nanocomposite. The ternary nanocomposite was employed as photocatalyst and exhibited degradation efficiency (97%) against rhodamine B dye under 180 min of irradiation time. The kinetic studies of dye on the photocatalyst surface were accurately explained by a first-order kinetics model, with all R2 > 95, signifying a strong correlation between time and dye concentration. The potocatalytic degradation mechanism of ternary nanocomposite was proposed based on band positions of of NiO, ZnO and CaO forming double type II heterojunction. Furthermore, species trapping experiments employing different scavengers were carried out, revealing the active participation of OH● and O2●─ radicals in the degradation mechanism.

Synthesis and characterization of ZnO–NiO composites for efficient U(VI) scavenger

Synthesis and characterization of ZnO–NiO composites for efficient U(VI) scavenger

Rietveld refined structural, optical and temperature dependent impedance spectroscopy of NiO–ZnO heterostructure composite: Synthesized through solid state method for high-frequency devices

Multifunctional NiO–ZnO heterostructure composite powder is economically synthesized through a solid-state route having a crystallite size of 23 (±2) nm. Chemical composition is identified through FTIR, the peak associated with Zn–O is detected at 1049 cm−1. However, the peaks detected at 870 cm−1 and 590 cm−1 show Ni–O stretching vibrations. UV-DRS technique is employed to estimate the energy band gap (Eg) around 3.18 eV. The impedance studies confirmed the presence of a non-Debye-type relaxation mechanism, electrical parameters confirm the contribution of electroactive regions i.e. grains and interfaces. An equivalent circuit model (R-CPE) is employed to measure various electrical parameters. Adiabatic small polaron hopping model is applied to estimate activation energies for Ni+2 (0.30 eV), Zn+2 (0.35 eV), and bulk (0.32 eV) respectively. The hopping length at the interface is estimated at around 0.8 Å by employing Mott's variable range hopping model. Jonscher's power law (JPL) is used to fit ac conductivity data, and conclude activation energy around 0.3 eV. The conduction mechanism through the whole frequency range (1–107 Hz) is governed by correlated barrier hopping. Various physical parameters i.e. binding energy (Wm), hopping length, and barrier height compared throughout the whole temperature range (313–393 K). The rate of increase in real permittivity at low frequency is related to the disorder of the cation at sublattices. These results deduced potential for NiO–ZnO heterostructure composite for high dielectric permittivity with low tangent loss for high energy storage applications.

Bursting and transforming MOF into n-type ZnO and p-type NiO based heterostructure for supercapacitive energy storage

Metal-organic frameworks (MOFs) have been considered as great contender and promising electrode materials for supercapacitors. However, their low capacity, aggregation, and poor porosity have necessitated the exploration of new approaches to enhance the performance of these active materials. In this study, sphere-like MOF were in-situ grown and it subsequently burst, transformed into a desired metal oxide heterostructure comprising n-type ZnO and p-type NiO (ZnO/NiO-350). The resulting optimized flower-like structure, composed of interlaced nanoflakes derived from MOFs, greatly improved the active sites, porosity, and functionality of the electrode materials. The ZnO/NiO-350 electrode exhibited superior electrochemical activities for supercapacitors, compared to the parent MOF, bare n-type, and p-type counterparts. The specific capacitance can reach to 543 ​F ​g−1 at a current density of 1 ​A ​g−1. Theoretical modeling and simulations were employed to gain insights into the atomic-scale properties of the materials. Furthermore, an assembled hybrid device using active carbon and ZnO/NiO-350 as electrodes demonstrated excellent energy density of 44 ​Wh kg−1 at a power density of 1.6 Kw kg−1. After 5000 cycles at 10 ​A ​g−1, the cycling stability remained excellent 80 % of the initial capacitance. Overall, such evaluation of unique electrode with superior properties may be useful for the next generation supercapacitor electrode.

NO2 and NH3 detection using work function measurement of solvothermal synthesised ZnO–NiO nanocomposites: a case study

Work function measurement using Kelvin probe method has been demonstrated as an effective and novel approach towards detection of NH3 and NO2 gases using ZnO–NiO based nanocomposites. For this the nanocomposites were synthesised in different compositions using the solvothermal method. Formation of ZnO–NiO nanocomposites was confirmed using XRD and EDS studies. It is found that the nanoparticle morphology of NiO changes with different percentages of Zn addition. The work function of the sensing film was found to decrease and increase upon exposure to NH3 (1.51) and NO2 (1.18) gases owing to the reducing and oxidising nature of the test gases. Of the different composites, Zn0.75Ni0.25O exhibited highest sensor response towards the test gases. The increased response is attributed to the nanostructured morphology of the nanocomposite and the formation and collapse of the p-n heterojunction formed between p-type NiO and n-type ZnO. Besides, incorporation of NiO enhances the oxygen adsorption on the sensor surface assigned to the Ni2+ ions getting readily oxidised to Ni3+. Our results clearly suggest that the work function measurements could also be used as an effective way for NO2 and NH3 detection.

Morphostructural studies of pure and mixed metal oxide nanoparticles of Cu with Ni and Zn

Nano-scale interactions between pure metal or metal-oxide components within an oxide matrix can improve functional performance over basic metal oxides. This study reports on the synthesis of monometallic (CuO), bimetallic (CuO–NiO) and trimetallic (CuO–NiO–ZnO) oxide nanoparticles (NPs) via the co-precipitation method and investigation of morphostructural properties. All of the synthesized metal oxide NPs were calcined at 550 °C temperature and annealed under vacuum. In this work, we applied Scherrer formula, modified Scherrer equation, Williamson-Hall plots, and Halder-Wagner plots to calculate the average crystallite size. The XRD data analysis showed that average crystallite sizes of the as-synthesized metal oxide phases were between 4 nm and 76 nm and average diameters calculated from SEM image were between 15 nm and 83 nm. The XRD studies also disclosed that average crystallite size and lattice microstrain of the CuO phases remain almost same (43 nm–46 nm and 2.074×10−3 to 2.665×10−3) for pure CuO and mixed CuO–NiO; but in case of mixed CuO–NiO–ZnO it is found to decrease in size to 11 nm where lattice microstrain increases to 9.653×10−3. Line broadening of diffraction peaks from microstrain contribution was between 0.02 and 0.01. Degree of crystallinity (%) of CuO phases found to decrease from 81 to 71. Dislocation density of CuO phases found to increase from 6.63×10−4nm−2 to 12.68×10−3nm−2. X-ray density of CuO phases increased from 6.48 to 6.53 g/cm3. Where this calculated small dislocation density well agreed with the high crystallinity. Crystal structure and specific surface area were determined from lattice constants and X-ray density. These synthesized nanopowders showed the existence of monoclinic, cubic, and hexagonal phases. The obtained NPs of multi-metal oxide explained more than one phases with different size, shape, and morphology at nano scale.

Removal of methylene blue dye by green synthesized NiO/ZnO nanocomposites

In this study, Justicia adhatoda leaf extract was used as both a reducing agent and a capping agent in a straightforward, environmentally friendly, and low-cost approach for the green synthesis of NiO/ZnO nanocomposites (NCs). The synthesized NiO/ZnO NCs were characterized by XRD, Rietveld refinement, UV–visible, FTIR, and SEM. The XRD and Rietveld Refinement studies have revealed the presence of two phases corresponding to hexagonal wurtzite ZnO and cubic NiO. The optical energy band gap (EGap) of prepared NiO/ZnO was 3.27 eV. SEM analysis revealed that the NiO-ZnO NCs have a cauliflower-like surface morphology with an average size of 89 nm. Under sunlight and UV illumination, the ability of NiO/ZnO NCs was evaluated to decompose methylene blue. NiO/ZnO NCs are very effective for methylene blue dye degradation under UV light following pseudo-first-order reaction kinetics, with a rate constant of 0.04625 min−1. Further, the scavenger study, hot filtration test, and reusability assessment were conducted to evaluate the catalyst's applicability and performance.

Microstructural, antifungal and photocatalytic activity of NiO–ZnO nanocomposite

Abstract In this work, NiO–ZnOnanocomposite (NC)was prepared through a facile, low-temperature,sol–gel route. Zinc acetate dihydrate, nickel chloride hexahydrate, cetyltrimethyl ammonium bromide (CTAB), and citric acid were used in the synthesis of the material. Then, the sample was kept in the muffle furnace at a temperature of 600°C for 2 h. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), UV–Visible spectroscopy, and photocatalytic and antifungal investigations were used to characterize the synthesized nanocrystallites. The XRD data showedthe polycrystalline hexagonal ZnO nanoparticles and cubic NiO crystallites. FTIR studies confirmed the presence of Zn-O and Ni-O bonds in the sample. The FESEM analysis showed the morphology of nanocrystallitescharacterized by their homogeneous shape and size. The absorbance curves from the UV–Visible spectroscopy investigation revealed the bandgap of 3.17 eV. The research findings demonstrate that the NiO–ZnO NC possesses the significant level of selected microbial pathogens. Industrial dyesmake water unhealthy for drinking. Among these dyes, methylene blue (MB) is toxic, carcinogenic, and non-biodegradable, and causes a severe threat to human health and environmental safety. Hence, it is necessary to develop efficient and environmentally friendly technology to remove MB from wastewater. The ZnO–NiO NC degraded the MB dye pollutant under visible irradiation (125 W), according to photocatalytic tests. After 120 min of exposure, the photocatalytic investigations demonstrated 75% degradation efficiency.

Nanosheet assembled NiO-doped-ZnO flower-like sensors for highly sensitive hydrogen sulfide gas detection

Hydrogen sulfide (H2S) gas is a dual menace since it is not only hazardous to human health and the environment, but it is also flammable. Given these crucial considerations, the need for competent gas sensors for H2S detection becomes apparent. In this endeavor, an investigation of the gas-sensing prowess inherent in sensors made from assembled nanosheets of ZnO–NiO arranged into intricate flower-like structures. The sensing materials were prepared using a straightforward solvothermal process. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to thoroughly examine the sensor's chemical properties and structural composition. The gas-sensing abilities of the sensing materials were rigorously assessed, which included a close examination of their electrical response to varied concentrations of H2S. The efficacy of the sensors may be due to the synergistic interactions between their distinct flower-like design, endowing them with an expansive surface area for optimum gas adsorption, and the significant catalytic impact supplied by the composition of ZnO–NiO. The results show that the ZnO–NiO flower-like sensors have high sensitivity, selectivity, and stability to H2S gas. Within the studied range, the response and recovery times were 51.43 s and 38.11 s respectively at 250 °C in 100 ppm H2S. This amalgamation of attributes manifests as an enhancement in the sensors' gas-sensing capabilities, highlighting their suitability for such an application. This research complements the explanation offered by first-principles calculations based on Density Functional Theory (DFT) to dive into the fundamentals of this gas-sensing mechanism.

Low temperature dielectric study and photoconductive analysis of ZnO/NiO composite material

The sol-gel process was used to synthesize a ZnO–NiO composite material in this study. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the material, which confirmed the existence of both ZnO nanoparticles and NiO sheets in the composite. The composite material contained two distinct crystalline phases, the face-centered cubic phase of NiO and the hexagonal phase of ZnO. The composite's average crystallite size was determined to be 19.0 nm. The particle size of the composite material was calculated to be ∼121 nm. The band edge emission at 393 nm (3.15 eV) was measured using photoluminescence (PL) spectroscopy. The PL spectrum revealed other emissions as well. The dielectric properties of the material were studied at low temperatures in the frequency range of 20 Hz to 1 MHz, and it was found to have a low dielectric dissipation at high frequencies, making it suitable for use in high frequency microwave devices. Impedance data was fitted using Z-View software with a fitting error of <5%. Impedance spectroscopy revealed that the composite material had two dielectric relaxation processes related to the bulk and the grain boundary. Analysis of frequency dependent ac conductivity revealed Overlapping large-polaron hopping (OLPH) is responsible conduction mechanism in our case indicated by variation of temperature (200–280 K) dependent parameter “s” with temperature. Photoconductivity studies showed that the composite material had enhanced electrical conductivity and photoconductivity compared to pure ZnO and NiO. This makes it a promising candidate for use in optoelectronic applications such as solar cells, optical switches, and photodetectors. The responsivity of composite (0.86 mA/Watt) is found to be 10 times greater than that of the responsivity of NiO (0.085 mA/Watt).

Interfacial electronic state between hexagonal ZnO and cubic NiO.

The interface of two dissimilar materials gives rise to a myriad of interesting structural, magnetic, and electronic properties that may be utilized to produce novel materials with unique characteristics and functions. In particular, growing a cubic oxide film on top of a hexagonal oxide substrate results in such unique properties due to the conflict of their respective stabilization mechanisms within the interface layer. This study aims to elucidate the electronic properties of the interface between hexagonal ZnO and cubic NiO by analyzing the interface electronic states within epitaxial NiO films grown on ZnO substrates, expressed in the form of ultraviolet photoemission spectroscopy (UPS) for valence band structure and X-ray absorption spectroscopy (XAS) spectra for conduction band structure. This is accomplished through a modeling approach in which the film, substrate, and interface signals are assumed to be related to each other by a set of mathematical equations, and then rearranging and modulating the equations to obtain unique UPS and XAS spectra that depict the interface electronic states.

Evaluation of a ZnO–NiO/rGO hybrid electrocatalyst for enhanced oxygen reduction reaction (ORR) applications

ZnO–NiO nanorods combined with an rGO sheet tested as an electrocatalyst for the ORR.

UV-Activated ZnO–NiO heterojunction sensor for ethanol gas detection at low working temperature

UV-Activated ZnO–NiO heterojunction sensor for ethanol gas detection at low working temperature

A cooperative nanoscale ZnO–NiO–Ni heterojunction for sustainable catalytic amidation of aldehydes with secondary amines

Metal–metal hydroxide/oxide interface catalysts are valued for their multiple active sites, enabling synergistic reactions in close proximity for advanced catalytic applications.

Highly porous hierarchical NiO coated ZnO p-n heterostructure for NO2 detection

In the present work, NiO coated ZnO films have been deposited at various deposition times such as 1, 2, 4 and 8 h using chemical bath deposition (CBD) method. X-ray diffraction (XRD) study showed the presence of both hexagonal ZnO and cubic NiO crystal structures. The field emission scanning electron microscopy (FE-SEM) images reveal the porous hierarchical microflower-like morphology. The atomic force microscopy (AFM) micrographs exhibit a maximum surface roughness of 174 nm. Brunauer Emmett-Teller (BET) shows the higher surface area of 31.41 m2/g. X-ray photoelectron spectroscopy (XPS) study showed the presence of Zn-2p3/2 and Zn-2p1/2 for Zn2+ oxidation state in ZnO whereas Ni-2p3/2 and Ni-2p1/2 for Ni2+ oxidation state in NiO. The NiO coated ZnO film shows the response of 76.5 % to 100 ppm NO2 at working temperature of 150 °C with Tresponse = 12 s and Trecovery = 140 s. Finally, NO2 sensing mechanism is proposed.

Impacts of BaO additions on structure, linear/nonlinear optical properties and radiation shielding competence of BaO–NiO–ZnO–B2O3 glasses

The purpose of this research is to study the structure, optical and radiation shielding effectiveness of radiation shielding glasses based on the formula [x BaO–(80-X) B2O3– 1NiO–11ZnO]; x = 8, 16, 24 and 32 mol%] have been obtained from melt quenching method. The density was increased from 2.861 (± 0.001) g.cm−3 to 3.119 (± 0.001) g.cm−3 due to an effective concentration of BaO. Furthermore, the vibrational investigations confirmed the conversion from trigonally-coordinated boron units (B O3) to tetrahedrally-coordinated boron units (B O4) with progressive enhancement in tetrahedrally-coordinated boron ratio (N4), besides a significant deterioration in non-bridging oxygen units (NBOs) inside the glass network due to the further concentrations of BaO. Optical studies showed the increase in optical band gaps from 3.22 (± 0.01) eV to 3.40 (± 0.01) eV with further concentrations of BaO from 8 to 32 mol%. This increment was attributed to the reduced NBO concentrations inside the glass network. Moreover, the nonlinear optical parameters showed decreased values due to the effective addition of BaO. Furthermore, the radiation shielding studies showed that the addition of BaO to the present glasses is an effective way to improve their radiation shielding performance. Additionally, to better understand the radiation protection provided by these glasses, a comparison of their half-value layers (HVL) with those of previously reported glasses was carried out at 0.662 MeV of photon energies. This comparison confirmed the improved radiation shielding performance of the present glass system.

Highly operative near full spectrum Cu doped NiO/ZnO photocatalyst: Photodegradation of phenol and organic dyes

In this study, new and near full spectrum photocatalyst composed of Cu doped NiO/ZnO composite with higher photodegradation activity (95–99%) for phenol, malachite green (MG) and reactive yellow 145 (RY145) was realized. The simple and low cost coprecipitation method was used to synthesis the pure ZnO, NiO, NiO/ZnO and 5 wt% Cu doped NiO/ZnO catalysts. The crystal structure analysis of all samples confirmed the formation of hexagonal ZnO and cubic NiO phases and ruled out the reaction between constituents. The transmission electron microscope images of the powders demonstrates the synthesis of nanostructures particles with mean size of 41–46 nm and nearly have spherical shape with some nano-sheets, especially for Cu doped NiO/ZnO sample. Optically, Cu doped NiO/ZnO nanocomposite exhibits two main band gap energies of 3.4 eV (NiO) and 2.88 eV (ZnO) with high and extended absorption tail until 1 eV, indicating the wide absorption capacity for most sunlight spectrum. The experiments of the photodegradation under natural sunlight prove that Cu doped NiO/ZnO nanocomposite has superior removal activity towards 30 ppm MG, 30 ppm RY145 and 15 ppm phenol with efficiency of 97% (60 min), 99% (70 min) and 95% (120 min), respectively. The radicals capture tests using different scavengers verify the main role of the superoxide (O2˙ˉ) species in the photodegradation process, followed by hydroxyl (OH˙) radicals. The reusability of Cu doped NiO/ZnO nanocomposite for four runs shows excellent photocatalytic activity (>90%) for MG and RY145 and phenol pollutants, reflecting the high stability for practical uses. The superior photoactivity characteristics of Cu doped NiO/ZnO photocatalyst were attributed to the integration between p-n heterojunction and Cu doping which reinforce the wide-ranging absorption and the separation of the electron-hole pairs.