NiO Particles Research Articles

Structural Features Investigation of a Highly Dispersed NiO–SiO<sub>2</sub> Catalyst by X-Ray Analysis of the Atomic Pair Distribution Function

In the present work NiO and NiO–SiO2 were investigated by X-ray diffraction and radial atomic pair distribution methods. By X-ray diffraction method, it was determined that the NiO particle sizes have coherent scattering region of more than 100 nm, while the NiO–SiO2 sample has a particle size of about 2–3 nm. At the same time, full-profile Rietveld simulation does not describe the effects observed on diffraction: the asymmetry of peaks, the appearance of an additional shoulder of peak 111 in the area of small angles, so the radial atomic pair distribution method was used to analyze the structure. During the simulation of the experimental atomic pair distribution curve, 3 different models were used: pure NiO, a mixture of NiO and Ni2SiO4, and a modified NiO model with Si embedded in the lattice. The latter model was created based on the assumption of silicon incorporation into the NiO structure, which can be evidenced by X-ray diffraction data. According to the results of radial atomic pair distribution modeling it is the latter model that gives the best description of the observed effects: significantly increased unit cell parameter, compared to the sample without SiO2 addition, as well as decreased metal cation–oxygen distances in the structure, while cation–cation distances are increased.

Investigation of Corrosion Behavior of Cenosphere reinforced Iron Based Composite Coatings

In the present study cenopshere was reinforced with FeCrNiC (Metco 42C) as matrix material and prepared four different feedstock powders such as FeCrNiC+0%Cenosphere, FeCrNiC+5%Cenosphere, FeCrNiC+10%Cenosphere and FeCrNiC+15%Cenosphere were coated by plasma spray technique on T22 substrate. Evaluation of the substrate and coatings potential under salt spray test was performed. Dense fog of 5% NaCl salt water was used to create a corrosive atmosphere within the chamber. The salt water's pH was kept constant at 6.5-7. The materials that underwent corrosion were examined using X-ray diffraction (XRD), and scanning electron microscopy (SEM). The FeCrNiC+15%Cenosphere and FeCrNiC+10%Cenosphere coatings exhibited reduced weight loss during a 168-hour corrosion test compared to the FeCrNiC+5%Cenosphere, FeCrNiC coatings, and substrate. The excellent chemical stability and corrosion resistance of Cr23C6, SiO2, NiO, and Cr2O particles contribute to gradually avoid the formation of red rust on Fe-based coated samples with exposure approaches to 52 and 130 hours.

Highly dispersed Ni nanoparticles confined in mesoporous SBA-15 for methane dry reforming with improved coke resistance and stability

Methane dry reforming (DRM) is a promising route for sustainable syngas production, in which Ni-based catalysts face challenges of metal sintering and coke formation. In this work, highly dispersed Ni nanoparticles (NPs) embedded in the mesopores of SBA-15 were prepared using a simple solid-state impregnation (SSI) method. TEM and cross-section HRTEM results clearly indicated that ultra-small Ni NPs (3–4 nm) were orderly dispersed within the mesopores of the SBA-15 support. Compared with the conventional wetness impregnation (WI) method, the Ni/SBA-15 catalyst prepared by solid-state impregnation method possessed much better catalytic activity, stability, and coke resistance in DRM. In-situ DRIFTS and semi-in-situ XRD were used to elucidate the dispersion and encapsulation mechanism of Ni within the mesopores of SBA-15 during the sample preparation process. Specifically, WI formed large NiO particles, while SSI formed smaller NiO NPs with stronger interaction between metal and support (SIMS) via forming Ni-O-Si species which is beneficial for the DRM reactivity. This work establishes relationships among catalyst preparation, structure, and DRM performance, paving the way for general template-assisted methods to prepare nanometallic catalysts for various applications.

Co-doping regulation on Ni-based electrocatalysts to adjust the selectivity of oxygen reduction reaction for Zn-air batteries and H2O2 production.

Although Ni-based materials are widely used as electrocatalysts, it remains necessary to further explore their selectivity towards the four- or two-electron oxygen reduction reaction (ORR). Herein, it is proposed to synthesize NiO@NCNTs (NCNTs = N-doped carbon nanotubes) using a metal-organic framework (MOF), [Ni(BZIDA)(H2O)]n (NiMOF, BZIDA = benzimidazole-5,6-dicarboxylic acid), as a precursor after calcination with dicyandiamide (DCDA). Regarding NiO@NCNTs, small NiO particles are distributed in NCNTs derived from DCDA homogeneously. NiO@NCNTs act as a typical two-electron electrocatalyst. The H2O2 production rate of NiO@NCNTs reaches 0.5 mol g-1 h-1 at 0.46 V (vs. RHE). After the doping of Co2+ in NiMOF, Co/NiO@NCNTs were synthesized using a similar method, with the four-electron character shown in ORR. A Zn-air battery was assembled by applying Co/NiO@NCNTs as the cathode material. When discharge occurs at 5 and 10 mA cm-2, its specific capacitance reaches 779.3 and 832.2 mA h g-1 with an energy density of 928.6 and 948.5 W h kg-1, respectively. Theoretical calculations suggest a variation in ORR selectivity between NiO@NCNTs and Co/NiO@NCNTs, which results from their different interactions with OOH*. This study demonstrates the effect of the structure on ORR selectivity for Ni-based electrocatalysts.

Performance improvement of NiO/YSZ sensitive electrode for high temperature electrochemical NOx gas sensors

In the mixed-potential gas sensor, the electrode type, particle size, microstructural morphology, as well as the interface state between the oxide-sensitive electrode and the solid electrolyte, are the key factors for determining the magnitude of the mixed potential. NiO-based material with the addition of Y2O3-stabilized ZrO2 (YSZ) particles is considered as one of the promising sensitive electrode materials for preparing the mixed-potential NOx sensors due to its excellent gas sensitivity. In this paper, the preparation technology of NiO-sensitive electrodes is developed and optimized for improving NOx (NO and NO2) gas-sensitivity properties of the NOx sensors. The experimental results show that the addition of YSZ can effectively improve the agglomeration morphology of NiO particles in the NOx-YSZ-based electrode material during high temperature sintering (i.e. 1200 °C) and enhance the bonding strength with the solid electrolyte. The sensor which was prepared by using the developed NOx-YSZ-based electrode material with the YSZ addition of 20 wt% has the most sensitive response characteristic to NO gas, and its response potential value increases with NO gas concentration. Elevating electrode sintering temperature can increase the size of NiO particles and shorten the length of the three-phase boundary (TPB) in the sensitive electrode. The average length of TPB is the longest in the sensitive electrode sintered at 1000 °C which corresponds to the best sensitive response to NO gas. The sensitive electrode's thickness also affects the NO response sensitivity, and the sensor with an electrode thickness of 14 μm has the most NO response sensitivity. In addition, the NO/NO2 gas mixture test results indicate that the current developed sensor is more sensitive to NO2 gas than that of NO gas.

Facile synthesis of Ni-doped zeolite-based catalysts from waste coal gasification fine slag for steam reforming of toluene

The preparation of efficient and stable catalysts for biomass tar reforming using low-cost solid waste is of great value for achieving green biomass gasification. In this work, new porous Ni-doped zeolite catalysts were formed by an ion exchange method making use of the waste CGFS as the precursor. At a proper NiO loading content, the catalyst (Na@Air-0.2Ni) exhibits a uniform spherical particle-linked porous structure with NaAlSiO4 as the supporting matrix and NiO particles anchoring on the surface as active sites. The catalytic performance of the catalysts was investigated in toluene reforming experiments to evaluate their potential for biomass tar conversion. Under optimized conditions (720 °C, S/C = 1.5, and N2 flow 25 mL/min), toluene conversion reached 92 % using Na@Air-0.2Ni as a catalyst, yielding 2500 μmol/min CO and 2800 μmol/min H2. Continuous steam reforming of toluene formed to FeNi3 alloy, which in turn strengthens the stability of the catalyst, and a high toluene conversion of 81 % can be achieved in 450 min continuous experiment, indicating the excellent stability of the catalyst. This work has confirmed that coal gasification slag rich in silicon and aluminum has the potential to prepare new zeolite-based catalysts, which is an important exploration for promoting high-value conversion of solid waste.

Porous NiO/Ni foam composites for improved impedance match and electromagnetic wave absorption through a simple in-situ calcination process

Light weight is a significant target for the magnetic metal-based electromagnetic wave (EMW) absorbents. Constructing foams with porous structure and low density has been proved to be a feasible way. However, the high conductivity of the metal foam will bring a poor impedance match, which hinders the EMW absorbing property. Herein, we reported a facile one-step calcination strategy for the magnetic metal foams toward improved impedance match. The NiO/Ni foam composites were obtained with NiO particles in situ grown on the surface of foams. Greatly enhanced EMW absorption performance was obtained with minimum reflection loss (RLmin) of −39.71 dB at a frequency of 13.6 GHz and a thickness of 2.0 mm. Meanwhile, the effective absorption bandwidth (EAB) could reach 5.15 GHz. The introduction of surface NiO weakens the conductivity of pure metals and the abundant pore structures of NiO as well as the inherent three-dimensional (3D) networks of metal foams further promote the multiple reflections and scattering of the EMWs. Consequently, this work provides a feasible and convenient way for the massive production of magnetic metal foams as excellent EMW absorbents.

Evaluation of Homogeneous NiO Particles on ZnO Heterojunction: Insights into Its Properties for Antifungal Applications

Evaluation of Homogeneous NiO Particles on ZnO Heterojunction: Insights into Its Properties for Antifungal Applications

Investigation of microstructure evolution and redox behavior of Ni-GDC cermet by cyclic re-oxidation in CO2

The microstructure and reactivity of Ni-GDC cermet under cyclic oxidation in CO2 conditions were investigated using temperature-programmed reduction (TPR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The XRD results revealed that NiO was formed during the re-oxidation process in CO2. SEM and TPR results demonstrated that nanostructured NiO aggregates were formed on the surface of the sample after being re-oxidized at 400 °C for 1200 min, resulting in an α peak with high reduction activity and a conversion of only 16% from Ni to NiO. In contrast, the samples re-oxidized at 600 °C for 600 min and 800 °C for 240 min were completely oxidized, resulting in reconstructed and sintered NiO with larger particle size, and a β peak with lower reactivity and a conversion of 100%. Redox cycling was further conducted on completely oxidized samples, which showed a decrease in β peak temperature from the first to seventh cycle. The migration and redistribution of sintered NiO towards the exterior were confirmed by comparing SEM images after the first and fourth cycles, which favored an increase in the reactive area. Therefore, this study reveals that lower re-oxidation temperatures (≤400 °C) and an appropriate increase in redox cycles are beneficial for forming surficial nanostructures while hindering the formation of large sintered NiO particles.

Constructing NiO/Co3O4/KNbO3 heterostructure with NiO and Co3O4 particles coupled on KNbO3 cubes for high-performance urea-assisted alkaline oxygen evolution reaction

In this study, a novel NiO/Co3O4/KNbO3 heterostructured electrocatalyst with NiO and Co3O4 particles coupled on KNbO3 cubes was constructed using simple sol–gel and calcination processes. The formation of multiple interfaces between NiO, Co3O4, and KNbO3 in the heterostructure contributed to a synergistic effect, adjusted the electronic structure, and generated abundant active sites at the interfaces. As a result, the NiO/Co3O4/KNbO3 electrocatalyst exhibited remarkable urea electrolysis performance, including a low potential of 1.67 V at 100 mA cm−2 and a small Tafel slope of 29 mV dec−1. Furthermore, the change in the overpotential was negligible even after a rigorous stability test of 3000 cycles, highlighting its exceptional durability and reliability. This study provides a novel structural engineering strategy for achieving efficient hydrogen production and purification from urea-containing wastewater.

About the nickel amount deposited on silica-alumina for ethylene production through oxidative dehydrogenation of ethane

This work explores the deposition of different nickel amounts (20 – 80 wt% Ni) on a silica-alumina support to prepare catalysts for ethylene production through the oxidative dehydrogenation of ethane (ODHE). The nickel species features and their distribution on the support had an important effect on their reducibility and interactions, and consequently on their catalytic performance. At low nickel loadings (20 – 40 wt%) highly ethylene-selective formulations were obtained driven by small and well-distributed NiO particles with moderate-to-hard reducibility and high interaction with the support. Contrarily, higher nickel amounts generated bigger NiO aggregates and more reducible Ni2+ species. Therefore, the NiO-support interactions got weakened and ethylene selectivity suffered a slight drop for nickel contents of 50 and 60 wt% and an additional decrease for 80 wt%. Nevertheless, all catalysts maintained a remarkable selectivity to ethylene even with an increased ethane conversion, demonstrating the valuable capacity of this novel support.

Low-temperature hydrogen production from waste polyethylene by nonthermal plasma (NTP)-assisted catalytic pyrolysis using NiCeOx/β catalyst

Conventional catalytic pyrolysis of waste plastics for H2 production faces challenges due to excessively high reaction temperatures. This study introduced a NiCeOx/β catalyst for low-temperature H2 production from polyethylene (PE), aiming to enhance H2 yield through nonthermal plasma (NTP) and catalytic active sites. Experimental results confirmed the efficacy of NTP in promoting collision between high-potential-energies active species and plasma-catalyst interactions, identifying acidic sites as primary catalytic active sites. Both experiments and density functional theory (DFT) calculations confirmed NiO and CeO2 particles as metallic active sites, exhibiting thermodynamic and kinetic benefits for primary products from PE pyrolysis. Under optimal conditions, the highest H2 yield and selectivity respectively reached 32.71 mmol/g and 82.10 % at a PE/(NiCeOx/β) ratio of 1:4, reaction temperature of 400 °C, and NTP discharge power of 210 W. The NiCeOx/β catalyst facilitated low-temperature pyrolysis of waste plastics, enhancing H2 selectivity and yield.

A study on the oxidative property using thermogravimetric analysis of NiO nanoparticles prepared by a simple wet chemical method

Nanosized NiO particles were synthesised by chemical co-precipitation technique and the particle has been characterized morphologically, elementally, structurally and thermally using High Resolution Scanning Electron Microscopy (HR-SEM), Energy Dispersive X-ray Spectroscopy (EDAX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). A green precipitated Nickel Oxide Nanoparticles (NiO NPs) was prepared and the size of the particle was found to be 45 nm and the presence of Ni and O elements were confirmed using the elemental analytic tools like EDX and FTIR in which the existence of water molecules was confirmed from the absorption spectrum. The generated sample's crystal structure was face-centered cubic, and Scherer's equation was used to compute its size, which was found to be 43 nm. Crystal characteristics including crystal parameters (a), interatomic distance (dh,k,l), atomic radius (r) and cell volume (Vc) were also calculated. The weight loss observed from TGA curve signifies the oxidative property of NiO NPs and there is a steady increase in the weight difference versus time difference. The calcination temperature of NiO was determined to be 700⁰C via analysis at the TGA curve's peaks. The activation energy (Ea) was determined using Coats-Redfern method by solving the slope of the graph between log[−log(1−α)T2] and 1000T. With respect to its highly effective capacity, which can be seen when treating with an increase in temperature, NiO may be used as an oxidising and reducing agent in oxidation and reduction processes.

Kinetic exploration of CO2 methanation over nickel loaded on fibrous mesoporous silica nanoparticles (CHE-SM)

A novel series of nickel (Ni) loaded on Fibrous Mesoporous Silica Nanoparticles (CHE-SM) support with varying Ni contents (x=1–30 wt%) were synthesized, denoted as xNi/CHE-SM and then investigated for carbon dioxide (CO2) methanation. The catalysts underwent comprehensive characterization using XRD, N2 adsorption-desorption, FESEM, FTIR-KBr, H2-TPR, and CO2-TPD techniques. The XRD and FESEM analyses confirmed the structural integrity of CHE-SM, irrespective of the Ni loading. However, the size of the nanocrystalline NiO particles appeared to be influenced by the Ni loading. Notably, 20Ni/CHE-SM exhibited the highest CO2 conversion of 92% at 350 °C, demonstrating its potential for low-temperature activation. H2-TPR and CO2-TPD results revealed favorable NiO reduction at lower temperatures, indicating medium-strength basicity that facilitated efficient CO2 and H2 adsorption and activation. Consequently, 20Ni/CHE-SM exhibited superior catalytic performance compared to other catalysts, with lower activation energy (61.5 kJ/mol). Kinetic studies focusing on 20Ni/CHE-SM indicated a molecular adsorption mechanism of CO2 and H2 on a single site after evaluation using four Langmuir-Hinshelwood models. This result was attributed to the high amount of medium strength basicity possessed by the 20Ni/CHE-SM catalyst which provided an abundance of adsorption sites, resulting in greater fractional coverage of reactants and enhancing the CH4 formation rate.

Microstructure and properties of in situ Al2O3 particle-reinforced aluminium alloy lattice rods fabricated by wire-arc-directed energy deposition

Lattice structures have great potential for application in the thermal protection systems of high-performance hypersonic vehicles (Mach > 5). They are lightweight, highly load-bearing and provide good heat insulation. Wire-arc directed energy deposition (WA-DED) is an effective method for preparing lattice structures made from metal lattice rods. A method is proposed to improve the ultimate tensile and compressive strengths of aluminium (Al) alloy lattice rods and lattice structures made by WA-DED. The replacement reaction of Al and NiO generates Al2O3, which was used to improve an Al–Cu alloy (2xxx series). An Al–Cu–NiO system cored wire filled with NiO particles was developed as the raw material for studying WA-DED lattice rods. Then the rod was heat treatment. Tests show that the strength of in situ Al2O3-particle-reinforced Al alloy rods was 281 MPa, which is 13.9% higher than that of Al–Cu 2319 Al alloy deposited rods. Reinforcement also increased the elongation (EL) from 11.3% to 13.5%. Strength is increased by Al and NiO reacting in situ to form an Al2O3 phase with refined grains. Most of the generated Ni is dissolved in Al2Cu to form a nano γ-Al7Cu4Ni phase, which plays a second-phase strengthening role. After T6 heat treatment, the strength and EL of 2319-NiO-cored wire deposited rods was 441 MPa and 10.4%. Fine, needle-like θ’-Al2Cu structures and Al2O3 and γ-Al7Cu4Ni nanoparticles pin dislocations, prevent their movement and improve the mechanical properties of the rod. The compressive strength of a planar lattice structure after T6 heat treatment was 105 MPa and its weight was only 15 g, demonstrating high specific strength. Finally, arc additive manufacturing with the developed 2319-NiO-cored wire was used to fabricate a curved-generatrix-shell pyramid lattice structure for use in the thermal protection cone of a hypersonic vehicle. Its thermal insulation coefficient was 82.5%, demonstrating excellent insulation performance. This study provides insights into the manufacturing of thermal protection systems for lightweight, high-strength and high-heat hypersonic vehicles.

High-Index NiO Particle Synthesis in Alkali Chloride Salts: Nonclassical Crystallization Pathways and Thermally-Induced Surface Restructuring.

The formation mechanism(s) of high-index facets in metal oxides is not widely understood but remains a topic of interest owing to the challenges of stabilizing high-energy surfaces. These metal oxide crystal surfaces are expected to provide unique physicochemical characteristics; therefore, understanding crystallization pathways may enable the rational design of materials with controlled properties. Here the crystallization of NiO via thermal decomposition of a nickel source in excess of alkali chlorides is examined, focusing on KCl, which produces trapezohedral NiO (311) particles that are difficult to achieve through alternative methods. Trapezohedral NiO crystals are confirmed to grow via a molten eutectic where NiO nucleation is followed by nonclassical crystallization through processes resembling colloidal assembly. Aggregates comprised of NiO nanocrystals form mesostructures that ripen with heating time and exhibit fewer grain boundaries as they transition into single-crystalline particles. At temperatures higher than those of NiO crystallization, there is a restructuring of (311) facets into microfacets exposing (111) and (100) surfaces. These findings illustrate the complex crystallization processes taking place during molten salt synthesis. The ability to generate metal oxide particles with high-index facets has the potential to be a more generalized approach to unlock the physicochemical properties of materials for diverse applications.

Role of citric acid in enhancing aromatic hydrogenation performance in Ni-HPW/SiO2 catalysts

In this study, we utilized a sol-gel method to prepare Ni-HPW/SiO2 catalysts with varying citric acid (CA):Ni molar ratios ranging from 0 to 5.0. The catalysts demonstrated different levels of activity in the hydrogenation of ethylbenzene, which correlated to their respective CA:Ni ratios. Introducing citric acid in the preparation process of nickel-based catalysts yielded mesopore formation and reduced NiO particle size, producing a more uniform NiO dispersion on SiO2, which was confirmed by BET, XRD, and TEM analyses. The results of H2-TPR, H2-TPD, NH3-TPD, and Py-IR analyses suggested that the addition of citric acid augmented the interaction between phosphotungstic acid (HPW), Ni species, and SiO2. Citric acid improved Ni species and HPW dispersion, fostering increased HPW-Ni species formation. This, in turn, generated additional electron-deficient Ni ions, stemming from semi-reduced HPW-Ni species, which acted as Lewis acid sites, enhancing Ni+ species effectiveness in activating aromatic rings. The better-dispersed, non-HPW-bound NiO, which, upon complete reduction to Ni, led to a substantial rise in H2 bond cleavage, thereby facilitating more hydrogen spillover. Overall, the infusion of citric acid into fabricating Ni-HPW/SiO2 catalysts sparked a significant surge in their aromatic hydrogenation ability.

Structural reconfiguration of Al/CaO adsorbent by Ni doping to improve sintering resistance and arsenic removal performance

CaO-based adsorbents have poor adsorption performance due to high temperature sintering. In this study, a trace amount of Ni was added to an Al/CaO adsorbent using the Pechini hydrothermal method and anhydrous grinding method. The modified adsorbent was then used to remove As2O3, and both experimental and theoretical approaches were employed. The experimental results showed that the addition of Ni transformed the surface of the adsorbent from a two-dimensional network structure to a three-dimensional cluster structure, significantly increasing its specific surface area and improving its adsorption capacity for As2O3. The adsorption capacity reached 933.1 mg/kg at 900 °C, which was 3.79 times higher than that of pure CaO and 8.2 times higher than that of Al2O3. Additionally, the presence of nano-scale NiO particles prevented the sintering of CaO grains, allowing the adsorbent to maintain its pore structure even after the reaction. Density functional theory (DFT) calculations showed that NiO was the most active site for As2O3 adsorption on the surface of Al/Ni-CaO. Ni acted as an electron transport bridge, enhancing electron transfer on the material's surface and increasing adsorption energy. These findings are important for future research on high-temperature removal of As2O3 with doped CaO-based adsorbents.

Study of NiO/Al2O3 and NiO/Zn-Al2O3 catalysts for water gas shift reaction

Nickel-based catalysts are of great importance for the generation of hydrogen from natural gas. Within this process, the conditions in which commercial NiO/Al2O3 is converted to Ni0/Al2O3 catalyst should be further investigated. A widely used technique to identify Ni2+ reduction conditions and the different compounds or types of particles in which this element is present is temperature-programmed reduction. In this work, the type of nickel oxide particles occurring on Al2O3 and ZnO-Al2O3-based supports were studied by different techniques, such as energy-dispersive X-ray spectroscopy, FTIR, the BET method, X-ray diffraction (XRD), and Temperature Programmed Reduction (TPR). All materials were evaluated in the water gas shift reaction (WGS), and the influence of their characteristics on the catalytic activity was assessed. Solids were prepared at different temperatures and Ni/Zn molar ratios. The results showed the presence of NiO in all materials, as well as the presence of ZnO, NiAl2O4, and ZnAl2O4 in materials prepared at higher temperatures. In all the materials calcined at the lowest temperature, the formation of NiO particles that fail to interact with the supports was prioritized. As the calcination temperature increased, NiO aggregates were formed, which, to a greater degree, interacted with the supports, whereby nickel aluminate was detected in all materials prepared at 750 °C. Zinc increased the selectivity but decreased specific surface area and activity through the WGS reaction. The solid labeled AZ15-500 showed higher activity and selectivity, reaching values of 100% for the water gas shift reaction.

Two–step pulsed laser ablation for preparation NiO@ZnO core-shell nanostructure and evaluation of their antibacterial activity

The excessive use of antibiotics led to the appearance of many strains of resistant bacteria, so it became necessary to use new antibacterial techniques. The aim of this work is the synthesis of novel core–shell NPs (NiO@ZnO) for antibacterial applications. A novel NiO@ZnO core–shell nanomaterial with a nanosize and uniform shape has been synthesised using the two-step pulsed laser ablation in liquid (PLAL) method. The first step is the laser ablation of the nickel target and the production of NiO NPs (core) colloidal, followed by the second step, the ablation of ZnO (shell) inside NiO NPs colloidal. The transmission electron microscopy results approve the formation of NiO@ZnO core–shell NPs with an average particle size of 54.4 nm for NiO particles and 60.7 nm for the NiO@ZnO core–shell. The antibacterial activity was examined against the pathogenic bacterial strains E. coli and S. aureus. We found that in the case of NiO, the inhibition rates were 62.4 and 59.2% for E. coli and S. aureus, respectively. While with NiO@ZnO NPs, this result was improved to 74.8% for E. coli and 71.2% for S. aureus. So, it was found that using the core–shell NPs increased the antibacterial activity of NPs, and the use of NiO NPs and core approved their effect as antibacterial agents due to their special properties. This behaviour is primarily because of the accumulation of the NiO@ZnO NPs on the surface of the bacteria, which leads to cytotoxic bacteria and a relatively increased ZnO, causing cell death. Furthermore, the use of a NiO@ZnO core–shell material will inhibit the bacteria from nourishing themselves on the culture medium. Therefore, core shelling metal oxides with another metal oxide or other material improves their antibacterial activity compared with using them alone.