Dispersed NiO Research Articles

Influence of Low Metal Loading on the Catalytic Activity and Stability of Supported Metal Catalysts for Methane Dry Reforming

This study aims to utilize highly active nickel catalysts supported by zirconia for the dry reforming of methane (DRM). The catalysts were prepared with a low nickel loading of 5 wt%. This study seeks to investigate how the limited nickel content (5 wt%) and various preparation methods impact the properties of the catalysts as well as their performance during the DRM reaction. To assess the physicochemical properties of the catalysts, several techniques were employed, including X-ray diffraction (XRD), N2 physisorption, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The evaluation of the activity and stability of the synthesized catalysts demonstrated that a specific configuration of the Ni/ZrO2 catalyst exhibited the best performance. The study further revealed a clear distinction between the two preparation methods. Catalysts prepared via co-precipitation displayed high activity of methane conversion (53%) and carbon dioxide conversion (55%) across all tested temperatures and maintained stability throughout the reaction. In contrast, catalysts synthesized through impregnation exhibited lower activity at all temperatures and were deactivated during the testing period. The observed catalytic activity can be attributed to a combination of factors, including highly dispersed NiO particles and a high number of oxygen vacancies within the catalyst structure. These findings underscore the critical role of catalyst preparation methods and the resulting physicochemical properties, such as phase composition and particle size, in determining catalytic performance. This highlights the potential for further enhancing the performance of these catalyst systems through optimization of preparation methods and exploration of novel support materials for the development of more efficient and sustainable DRM technologies.

Application of yttria stabilized zirconia (8YSZ), and NiO precursors for fabrication of composite materials for anode-supported SOFCs

In this paper, optimization of the manufacturing technology of bilayer supporting anode substrates for planar solid oxide fuel cells using precursors is carried out. The bilayer supporting anode substrates for the second generation planar SOFCs were fabricated by tape casting technique. In order to prepare a composite material for a current-collecting layer containing 60 vol. % NiO and a functional layer containing 40 vol. % NiO (proportions were chosen due to percolation theory), nickel sulfate heptahydrate NiSO4·7H2O was used. The composite mixture of 8YSZ/NiSO4 was calcined at a temperature of 1000°С. Application of NiO precursor led to the obtaining of a strong anode substrate that retains mechanical stability during redox cycling. The fine dispersion of NiO in a thin functional layer led to a high density of three-phase boundaries, which positively affected the electrochemical activity of the anode. Model samples of solid oxide fuel cells were made on the base of the manufactured anode substrates, its electrochemical behavior was investigated using standard electrochemical techniques. The power density at an operating temperature of 750°С was 1 Wt/cm2.

Graphitic carbon nitride functionalized with NiO nanoaggregates: An X-ray photoelectron spectroscopy investigation

The design and synthesis of low-cost oxygen evolution reaction (OER) photoelectrocatalysts endowed with high activity and durability is of utmost importance for sustainable energy generation via solar-assisted water splitting. In this regard, and in the framework of our recent activities, we have focused on the electrophoretic deposition of graphitic carbon nitride (gCN) specimens containing dispersed NiO nanoaggregates on carbon cloth substrates. In the present study, the attention is devoted to the x-ray photoelectron spectroscopy characterization of a representative gCN–NiO specimen. In particular, we provide an analysis of C 1s, N 1s, O 1s, and Ni 2p regions, discussing in detail the main spectral features. The obtained results, that provide evidence for a direct electronic interplay between the single material components, may serve as a useful comparison for additional research on analogous materials for energy and environmental applications.

Graphitic Carbon Nitride Structures on Carbon Cloth Containing Ultra- and Nano-Dispersed NiO for Photoactivated Oxygen Evolution.

The development of low-cost and high-efficiency oxygen evolution reaction (OER) photoelectrocatalysts is a key requirement for H2 generation via solar-assisted water splitting. In this study, we report on an amenable fabrication route to carbon cloth-supported graphitic carbon nitride (gCN) nanoarchitectures, featuring a modular dispersion of NiO as co-catalyst. The synergistic interaction between gCN and NiO, along with the tailoring of their size and spatial distribution, yield very attractive OER performances and durability in freshwater splitting, of great significance for practical end-uses. The potential of gCN electrocatalysts containing ultra-dispersed, i. e. "quasi-atomic" NiO, exhibiting a higher activity than the ones containing nickel oxide nanoaggregates, is further highlighted by their activity even in real seawater. This work suggests that efficient OER catalysts can be designed through the construction of optimized interfaces between transition metal oxides and carbon nitride, yielding inexpensive and promising noble metal-free systems for real-world applications.

Nanoparticles of NiO and CoO simultaneously dispersed on a mesoporous carbonaceous support as bifunctional electrocatalysts for ORR and OER reactions and Zn-air battery performance

This work aims to study the effect of different atmospheres and temperatures in the synthesis of a bifunctional electrocatalyst for ORR and OER reactions in the cathode of a Zn-air battery, using a carbonaceous support for dispersing Ni and Co species. At 300 °C, NiCo2O4 with a size of 4.93 nm under O2 and 150.14 nm using air, were obtained. These materials exhibited low specific surface area and pore volume and failed to show bifunctional activity. Instead, the simultaneous dispersion of NiO and CoO nanoparticles, with a size of 2.55 nm was achieved at 300 °C under N2 (NiCo/MC-N300), leading to a surface enrichment in Co2+ and Ni2+ species, while Ni and Co nanoparticles, 12.81 nm, were obtained at 700 °C under N2 (NiCo/MC-N700). These catalysts exhibited high specific surface area and pore volume, and bifunctional electrochemical activity; as well as high specific-capacity in a home-made Zn-air battery.

Performance of NiO doped on alkaline sludge from waste photovoltaic industries for catalytic dry reforming of methane.

Alkali sludge (AS) is waste abundantly generated from solar photovoltaic (PV) solar cell industries. Since this potential basic material is still underutilized, a combination with NiO catalyst might greatly influence coke resentence, especially in high-temperature thermochemical reactions (Arora and Prasad, RSC Adv. 6:108,668-108688, 2016). This paper investigated alkaline sludge containing 3CaO-2SiO2 doped with well-known NiO to enhance the dry reforming of methane (DRM) reaction. The wet-impregnation method was used to prepare the xNiO/AS (x = 5-15%) catalysts. Subsequently, all catalysts were tested by using X-ray diffraction (XRD), nitrogen adsorption/desorption (BET), temperature-programmed reduction of hydrogen (H2-TPR), temperature-programmed desorption of carbon dioxide (TPD-CO2), field emission scanning electron microscopy (FESEM-EDX), and X-ray photoelectron spectroscopy (XPS). The spent catalysts were analyzed by thermogravimetric analysis (TGA/DTG), transmission electron microscopy (TEM), and temperature-programmed oxidation (TPO). The catalytic performance of xNiO/AS catalysts was investigated in a fixed bed reactor connected with gas chromatography thermal conductivity detector (GC-TCD) at a CH4:CO2 flow rate of 30 mL-1 during a 10-h reaction by following (Shamsuddin et al., Int. J. Energy Res. 45:15,463-15,480, 2021d). For optimization parameters, the effects of NiO concentration (5, 10, and 15%), reaction temperature (700, 750, 800, 850, and 900 °C), catalyst loading (0.1, 0.2, 0.3, 0.4, and 0.5 g), and gas hourly space velocity (GHSV) range from 3000, 6000, 9000, 12,000, and 15,000 h-1 were evaluated. The results showed that physical characteristics such as BET surface area and porosity do not significantly impact NiO percentages of dispersion, whereas chemical characteristics like reducibility are crucial for the catalysts' efficient catalytic activity. Due to the active sites on the catalyst surface being more accessible, increased NiO dispersion resulted in higher reactant conversion. The catalytic performance on various parameters that showed 15%NiO/AS exhibited high reactant conversion up to 98% and 40-60% product selectivity in 700 °C, 0.2 g catalyst loading, and 12,000 h-1 GHSV. According to spent catalyst analyses, the catalyst was stable even after the DRM reaction. Meanwhile, increased reducibility resulted in more and better active site formation on the catalyst. Synergetic effect of efficient NiO as active metal and medium basic sites from AS enhanced DRM catalytic activity and stability with low coke formation.

Binary NiCu oxide nanoparticles onto graphite as promoting nanocatalysts for ethanol electro‐oxidation process

A facile and reduced cost fabrication protocol was followed to have a series of nickel oxide nanospecies onto graphite support with introducing varied copper oxide wt.% values (NiCuO/T). The co‐precipitation of metallic hydroxide particles onto carbonaceous surfaces and their subsequent burning at 400°C were sufficient to prepare mixed transition metal oxides. Suitable analysis tools were exploited to fully characterize the obtained nanopowders using scanning electron microscopy, transmission electron microscopy, X‐ray diffraction spectroscopy, X‐ray photoelectron spectroscopy, and energy dispersive X‐ray analysis. Outstanding performances of the formed nanocatalysts for catalyzing ethanol electro‐oxidation reaction were measured especially in presence of 15 wt.% copper oxide content. The onset potential (Eonset) value of alcohol oxidation process was negatively shifted at dispersed NiO nanoparticles onto graphite after doping with copper oxide nanospecies. This promoted activity of prepared nanomaterials could be explained by their increased active sites when binary metallic oxides were incorporated. Electrochemical impedance spectroscopy studies demonstrated much lowered resistances in alkaline solution containing ethanol molecules to ascertain the enhanced behavior of NiCuO/T nanocatalysts. Moreover, their good stability attitude encouraged the application of doped nanomaterials with copper oxide for fuel cells application.

A novel approach to tailoring the microstructure and electrophysical properties of Ni/GDC-based anodes by combining 3D-inkjet printing and layer-by-layer laser treatment

This work proposes an original method for tailoring the microstructure and electrical properties of Ni/GDC anodes by using 3D inkjet printing of high-viscosity functional compositions with intermediate laser treatment of each layer after each printing pass. Based on a mixture of highly dispersed oxides NiO and CeO2 doped with gadolinium (GDC), paste formulations for 3D inkjet printing have been developed. The effects of 3D printing and laser treatment conditions on the porosity and shrinkage ratio of the NiO/GDC anodes during sintering were investigated. The reduction of the anode support workpieces to produce Ni/GDC cermet was carried out and the effect of laser exposure on the morphology and electrical characteristics of the resulting samples was studied. It was found that an increase in the laser exposure values during layer-by-layer laser treatment of printing compositions leads to a two-fold increase in the porosity of the solid oxide fuel cell components, an increase in the average pore size from 0.2 to 0.3 to 2–5 μm, and to a five-fold decrease in the sintering shrinkage ratio. It was also found that the electrical conductivity of the Ni/GDC cermet, produced by the reduction of the laser treated NiO/GDC, increased by 5–10 times as the laser exposure values increased. The influence mechanism of the layer-by-layer laser treatment of the original NiO/GDC samples on the electrical conductivity of their reduced counterparts, Ni/GDC cermet anodes, has been proposed. An increase in the electrical conductivity was shown to be due to in situ reduction of NiO, partial sintering of Ni nanoparticles and the formation of a percolation network. This new method of hybrid 3D printing opens up great prospects for tailoring the morphological and electrical characteristics of SOFC anode supports.

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.

Synthesis of Quasi-MOFs featuring special hub-and-spoke channels and surface NiO species for enhanced total hydrogenation of furfural

Quasi-MOF-74 catalysts, featuring spokewise channels, abundant Ni0 and highly dispersed surface NiO species, exhibited higher H donating ability and exhibited remarkable performance for converting FFR, achieving 98% THFA yields at 70 °C and 3 MPa H2.

Optical and structural characterizations of NiO-doped PMMA films and fabrication of Ag/NiO-doped PMMA/n-Si/AuSb for analogue-digital switching applications

Herein, the authors report the NiO-doped PMMA nanocomposites fabrication process with different Ni concentrations of 0.001–10 wt% on pre-cleaned glass, ITO, and n-type Si via spin-coating technique. X-ray diffraction (XRD) was used to analyze the crystal structure of NiO in powder form and the NiO-doped PMMA nanocomposite thin films. The Rietveld refinement method was used to analyze the manufactured NiO's powder-form structural characteristics. The analysis data revealed a single phase of NiO nanoparticles with face-centred cubic of Fm-3m space group. The average crystallites' mean size and the microstrain value were determined based on the Williamson-Hall model and were equal to 32.47 ± 1.210 nm and 5 × 10−5, respectively. The FESEM micrographs illustrate dispersed cubic-shaped NiO grains in the PMMA matrix. The estimated energy gaps and the width of the localized energy states (Urbach tails) are plotted against the photon energy. The estimated energy gap, EgOp is increasing from 3.649 ± 0.003 eV to 3.782 ± 0.005 eV with increasing the NiO nanoparticles' doping ratio in the PMMA as a host insulating polymer. The fabricated Ag/NiO-PMMA (S4)/n-Si/AuSb heterojunction device revealed two different (HRS and LRS) resistance-switching behaviours. For second and third electrical (I–V) paths, the extracted magnitudes of the ideality factor are 2.397 ± 0.006 and 2.691 ± 0.003 and the calculated barrier height are 0.727 ± 0.004 and 0.886 ± 0.005, respectively. The interfacial electronics states NSS increasing from 6.58 × 1012 to 3.7 × 1014 cm−2.eV−1 and 3.48 × 1013 to 3.65 × 1014 cm−2 .eV−1 for the 2nd HRS path and 3rd LRS, respectively. The investigated hysteresis loop and the variation in interfacial electronics states reveal that the NiO-PMMA nanocomposite may be promising in non-volatile memory and electrical switching electronic devices.

(Digital Presentation) Facile Fabrication of Nickel and Sc-Doped Zirconia Cermet Electrode Thin Film on YSZ Substrate Via Screen-Printing for Solid Oxide Electrochemical Cells

Solid oxide electrochemical cells (SOCs) operating as either solid oxide fuel cells (SOFCs) or solid oxide electrolysis cells (SOECs) are widely known as promising advancements in green energy technologies for storage and high-efficiency energy generation. This study used a single screen-printing deposition method to fabricate a porous Nickel – scandia-stabilized zirconia (Ni-ScSZ) cermet electrode on a dense YSZ solid electrolyte substrate. The precursor powders were prepared via the glycine-nitrate combustion process. To investigate the effect of ink slurry solvent on the quality, structure, and morphology of the deposited films, ethanol, and alpha-terpineol were used. The screen-printed films were sintered at 1300°C for 6h and reduced under an Ar/5% H2 gas environment at 700°C for 2h to form porous electrodes. X-ray diffraction (XRD) analysis showed that all sintered NiO-ScSZ films exhibited cubic peak structures of both NiO and ScSZ. Scanning electron microscopy (SEM) micrographs and elemental mapping revealed finer morphology with good dispersion of NiO and ScSZ phases for sintered NiO-ScSZ films with alpha-terpineol as solvent. After exposure to Ar/5% H2 gas environment, a complete reduction of NiO to Ni was revealed by XRD for all Ni-ScSZ electrodes. Moreover, SEM micrographs of as-reduced samples showed an increase in porosity as oxygen was removed from NiO. Electrochemical impedance spectroscopy was used to determine the conductivity of the reduced Ni-ScSZ electrode films under Ar/5% H2 gas environment. The obtained total conductivity values upon reduction are 9.54x10-5 S/cm and 4.75x10-5 S/cm for ethanol and alpha-terpineol as solvents, respectively.

Indium‐based Catalysts for CO2 Hydrogenation to Methanol: Key Aspects for Catalytic Performance

AbstractCO2 hydrogenation utilizing sustainably produced hydrogen and CO2 derived from industrial exhaust gas represents a pivotal technology for chemical energy storage and climate change mitigation. This work aims to identify the best combination of catalyst support, synthesis method and promotor for In2O3/ZrO2 catalysts in a typical fixed‐bed configuration. Intense characterization using ICP‐OES, XRD, XPS, N2‐physisorption, CO2‐TPD, H2‐TPR and SEM‐EDX provide molecular insights into the different effects caused by various synthesis methods and doping elements. Doping the most promising In2O3/ZrO2 (M‐SG) catalyst with 0.7 wt. % NiO by wetness impregnation using an ethanol/water mixture as a solvent, an increased methanol production rate of 0.497 gMeOH ⋅ ⋅ h−1 could already be achieved at 250 °C. Hereby, the low amount of highly dispersed NiO promotes H2 activation via hydrogen spillover, leading to sustained catalytic activity for 100 hours of time‐on‐stream.

Screen-Printing of NiO-ScSZ on YSZ Substrate Using Solid-State Reaction and Glycine-Nitrate Process Precursors for Solid Oxide Electrochemical Cells

Solid oxide electrochemical cells (SOCs) consisting of solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) are widely studied for the development of high-efficiency energy generation and storage devices. To investigate the effect of precursor particle size on the microstructural and morphological properties of the electrode, glycine nitrate process and solid-state reaction ball-milling were utilized as synthesis methods for Nickel oxide-scandia stabilized zirconia (NiO-ScSZ) powders. The synthesized powders were then screen-printed on commercial YSZ solid electrolyte substrates. The structure and morphology of the sintered electrodes were investigated. Particle size analysis (PSA) revealed that NiO-ScSZ precursor powders obtained from GNP ball-milled had a smaller average particle size than solid-state reaction ball-milled powders. For the sintered NiO-ScSZ films, cubic structures of both NiO and ScSZ have been observed from the X-ray diffraction (XRD) patterns. A better porous morphology with less agglomeration and better dispersion of NiO and ScSZ phases was revealed by the scanning electron microscopy (SEM) micrographs and elemental mapping for the GNP-ball-milled synthesized powders.

Catalytic CO2 hydrogenation to produce methane over NiO/TiO2 composite: Effect of TiO2 structure

In this study, TiO2 was morphologically engineered into three distinct structures, namely three-dimensional microparticles (MPs), zero-dimensional nanoparticles (NPs) and one-dimensional nanowires (NWs) to examine the effect of structure on CO2 methanation. Firstly, thermodynamic analysis was conducted, whereby it was observed that CH4 production is favoured at low temperature. Higher temperature will cause the CH4 selectivity to drop, in turn increasing the formation of other side products such as CO, C2H6 and solid coke. Then, Ni loaded on three different TiO2 supports, namely 3D TiO2 microparticles (MPs), 0D nanoparticles (NPs) and 1D nanowires (NWs), were prepared. It was noticed that the NPs have the smallest support particle size, followed by NWs and MPs. Despite TiO2 NWs having a larger particle size than NPs, the 15% Ni/TiO2 NWs boasted a higher surface area, smaller NiO crystalline and particle size, which resulted in an augmented NiO dispersion. Superior CO2 methanation performance with CO2 conversion, CH4 yield and selectivity of 88.44%, 87.53% and 98.97%, respectively was achieved over 15% Ni/TiO2 NWs. The stability of the TiO2 NWs counterpart over a 40 hours reaction time was the best among the three samples. Spent catalyst analysis also indicated that 15% Ni/TiO2 NWs are highly resistant to catalyst deactivation and coke formation. The prolonged durability was attributed to the 1D wire-like structure, which promoted a higher dispersion of active sites, facilitating an intimate contact between catalyst and reactants. The ameliorated dispersion also mitigates catalyst deactivation via sintering and coke formation. The findings elucidated that the morphology of the catalyst is more influential in enhancing the hydrogenation reaction than the support size.

The production and electrochemical performance of carbon nano-materials derived from plastics over nickel-based catalysts with different supports

This paper demonstrates a promising method for converting waste plastics into high-value carbon nano-materials as electrode materials. Therein, the catalytic performances of the three catalysts with different supports (Ni/γ-Al2O3, Ni/CaO and Ni/MgO) for carbon nano-materials derived from the catalytic cracking of low-density polyethylene in a two-stage reaction system were investigated. Compared with other carbon precursors, the hydrogen in the pyrolysis gas from plastics facilitated the growth of CNTs. Through the analysis of the physicochemical properties, the γ-Al2O3 support could improve the dispersion of NiO, which was beneficial to increasing the yield and uniformity of CNTs. The proper interaction of NiO with the γ-Al2O3 was conducive to improving the degree of graphitization of CNTs. The results showed that CNTs-A (from Ni/γ-Al2O3) obtained a specific capacitance of 32 F g−1 (0.5 A g−1, 6 M KOH), compared to CNTs-C (from Ni/CaO) and CNTs-M (from Ni/MgO) increased by 23% and 68%, respectively. It was demonstrated that CNTs-A with fewer defects, large specific surface area and high graphitization properties could achieve higher electrochemical performance by reducing the resistance during electron transfer.

Self-supporting NiO-coated activated carbon nanofibers based on atomic layer deposition for supercapacitor

The rapid development of consumer electronics, electric vehicles, and smart meters demands high-performance energy storage devices. By now, supercapacitors are expected to become one of the most promising energy devices for future energy technology. In this work, NiO nanoparticles supported on activated carbon nanofibers (NiO/ACNFs) have been synthesized by atomic layer deposition technique, which is directly used as self-supporting binder-free electrodes for supercapacitors. Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman results show that NiO nanoparticles (3.1 nm) are uniformly coated on ACNFs. The NiO/ACNFs-600 electrodes demonstrate a specific capacitance of 870 F·g−1 (1 A·g−1) and good rate capability (remain 67% at 10 A·g−1). The asymmetric supercapacitor devices with NiO/ACNFs-600//ACNFs electrodes yield a fairly high energy density of 39.85 Wh·kg−1 at 2000 W·kg−1 and excellent capacitance retention of 87% after 10,000 cycles. The excellent electrochemical capacitance performance for NiO/ACNFs is attributed to the high conductivity and large specific surface area of ACNFs, high capacity, small size, and even dispersion of NiO as well as the synergistic effect between them. These results demonstrate that NiO/ACNFs can serve as excellent electrode materials for high-performance asymmetric supercapacitors.

Synergistic Effect of Activated Carbon, NiO and Al2O3 on Improving the Thermal Stability and Flame Retardancy of Polypropylene Composites.

It is difficult to enhance the char yields of polypropylene (PP) due to the preferential complete combustion. Successful formation of abundant char layer structure of PP upon flammability was obtained due to the synergistic effect of NiO, Al2O3 and activated carbon (AC). From characterization of scanning electron microscopy (SEM) and transmission electron microscopy (TEM), it was revealed that the microstructure of residual char contained large amount of carbon nanotubes. Compared to the modification of AC, NiO and Al2O3 alone, the combination of AC, NiO and Al2O3 dramatically promotes the charring ability of PP. In the case of AC and NiO, NiO plays a role of dehydrogenation, resulting in the degradation product, while AC mainly acts as carbonization promoter. The addition of Al2O3 results in higher dispersion and smaller particle size of NiO, leading to greater exposure of active sites of NiO and higher dehydrogenation and carbonization activity. Compared to the neat PP, the decomposition temperature of the PP modified by combined AC, NiO and Al2O3 was increased by 90 ℃. The yield of residual char of AC-5Ni-Al-PP reached as high as 44.6%. From the cone calorimeter test, the heat release rate per unit area (HRR) and total heat release per unit area (THR) of PP composite follows the order AC-5Ni-Al-PP < AC-10Ni-Al-PP < AC-Ni-PP < AC-15Ni-Al-PP < AC-1Ni-Al-PP. Compared to the neat PP, the peak of HRR declined by 73.8%, 72.7%, 71.3%, 67.6% and 62.5%, respectively.

Monodispersed NiO Nanoparticles into SBA-15: An Efficient Nanocatalyst to Produce Ketone-Alcohol (KA) Oil by the Oxidation of Cyclohexane in Mild Conditions

A simple and efficient approach to preparing highly efficient and reusable NiO@SBA-15 nanocatalysts for the oxidation of cyclohexane to produce ketone-alcohol (KA) oil was reported. These nanocatalysts were prepared by the dispersion of NiO NPs into SBA-15 using a coordination-assisted grafting method. In this approach, four commercially available nickel salts were immobilized into amino-functionalized SBA-15. After washing and calcination, four new nanocatalysts were obtained. The high dispersion of NiO NPs into SBA-15 was confirmed by HR-TEM and XRD. Different oxidants such as O2, H2O2, t-butyl hydrogen peroxide (TBHP), and meta-Chloroperoxybenzoic acid (m-CPBA) were evaluated. However, m-CPBA exhibited the highest catalytic activity. Compared to different catalysts reported in the literature, for the first time, 75–99% of cyclohexane was converted to KA oil over NiO@SBA-15. In addition, the cyclohexane conversion and K/A ratio were affected by the reaction time, catalyst dose, Ni content, and NiO dispersion. Moreover, NiO@SBA-15 maintained a high catalytic activity during five successive cycles.

Nickel Oxide Nanoparticles on KIT-6: An Efficient Catalyst in Methane Combustion

KIT-6 silica with well-ordered three–dimensional (3D) mesopores has been synthesized as a support for nickel-based catalysts. Transmission Electron Microscopy (TEM) and low-angle X-ray Diffraction (XRD) analysis are used to ensure that the ordered 3D mesostructure is stable after NiO incorporation. In this study, the catalytic activities of the NiO/KIT-6 samples are investigated. Additionally, the results show that a 10 wt% NiO/KIT-6 catalyst exhibits high catalytic performance in methane combustion, with T10, T50 and T90 being only 386 °C, 456 °C and 507 °C, respectively. Hydrogen Temperature Programmed Reduction (H2-TPR) studies have shown that the interaction between NiO and KIT-6 in the 10 wt% NiO/KIT-6 catalyst is weak. Methane Temperature programmed Surface Reaction (CH4-TPSR) results show that the surface oxygen of the NiO/KIT-6 catalyst allows it to exhibit a high catalytic performance. NiO/KIT-6 catalysts exhibit superior activities to SBA-15, MCF and SiO2 support catalysts because KIT-6 has a higher surface area and ordered 3D mesopore connectivity, which is favorable for better NiO dispersion and peculiar diffusion for reactant and products. Furthermore, the used catalyst maintained an ordered mesostructure and reduction property.