Metal Oxide Composites Research Articles

Facile co-deposition of NiO-CoO-PPy composite for asymmetric supercapacitors

In this work, a novel 3-D Nanosheets of composite metal oxides of NiO-CoO and organic polypyrrole (PPy) are synthesized by facile one-step alternating current (AC) co-electrodeposition method on the surface of carbon cloth (CC) as a supercapacitor electrode. The growth process of the electrode is time-saving that the growth of electrode cost only 1 h. The NiO-CoO-PPy nanosheets display an excellent specific capacitance (1123 F g−1 (156 mAh g−1) at 1 A g−1) and remarkable cyclic stability (90.1% capacitance retention after 5000 cycles). Moreover, the asymmetric supercapacitor with NiO-CoO-PPy electrode and active carbon as counter electrodes exhibits an excellent energy density of 35.9 Wh kg−1 at a power density of 801 W kg−1. It suggests that the AC co-electrodeposition method is a highly effective way for the growth of composite metal oxides and organics supercapacitor electrode materials, which has great application value.

Boosting catalytic toluene combustion over Mn doped Co3O4 spinel catalysts: Improved mobility of surface oxygen due to formation of Mn-O-Co bonds

Catalytic combustion is considered as the most promising technology for removing VOCs over composite metal oxide catalysts. Herein, Mn doped Co3O4 spinel catalysts (MnaCo1-aOx) like spherical were successfully prepared via solvothermal method, and applied for catalytic toluene combustion. The physical and chemical properties of catalysts were analyzed by various characterization techniques such as XRD, N2 physical-adsorption, SEM, TEM, H2-TPR, O2-TPD, XPS and in-situ DRIFTS. Among these catalysts, Mn0.4Co0.6Ox shows optimal catalytic activity (T50 = 206 °C; T90 = 215 °C) and stability, and it can still maintain good activity even in presence of H2O. The amounts of the surface Co2+, Mn4+and lattice oxygen are improved based on the interaction between Co and Mn ions (Mn3+ + Co3+ → Mn4+ + Co2+), leading to far stronger oxidation ability of catalyst. The formation of the surface Mn-O-Co bonds on spinel catalysts MnaCo1-aOx improves the mobility of surface oxygen. In addition, the catalytic combustion of toluene over these catalysts follows the Mars-van Krevelen mechanism and the surface lattice oxygen plays a crucial role in the cycle of oxygen species based on in-situ DRIFTS results.

Fabrication of Superamphiphobic Surfaces via Spray Coating; a Review

AbstractSuperamphiphobic coatings that simultaneously repel both water and oil and are applicable to a wide range of surfaces are needed for use in self‐cleaning, anti‐icing, and antimicrobial coatings. Spray coating is a method that can be used to apply such coatings to a wide range of surfaces in a scalable and high throughput manner. This review presents a comprehensive overview of the materials architecture, synthesis, applications, and figures‐of‐merit of superamphiphobic surfaces that are deposited using spray coating. The design requirements of superamphiphobic surfaces—surface roughness and wettability, re‐entrant topographic features, and chemical composition—are initially introduced. Based on the material, different synthesis techniques are then discussed with a focus on metal oxides and metal oxide composites, polymers, emerging, and green materials. The areas of application of superamphiphobic coatings are also presented. Finally, the main hurdles in using such coatings in real‐life applications are discussed in depth, and emerging technologies for overcoming these challenges are presented.

Design and Analysis of Metal Oxides for CO2 Reduction Using Machine Learning, Transfer Learning, and Bayesian Optimization.

We aim to achieve resource recycling by capturing and using CO2 generated in a chemical production and disposal process. We focused on CO2 conversion to CO by the reverse water gas shift–chemical looping (RWGS-CL) reaction. This reaction proceeds in two steps (H2 + MOx ⇆ H2O + MOx–1; CO2 + MOx–1 ⇆ CO + MOx) via a metal oxide that acts as an oxygen carrier. High CO2 conversion can be achieved owing to a low H2O concentration in the second step, which causes an unwanted back reaction (H2 + CO2 ⇆ CO + H2O). However, the RWGS-CL process is difficult to control because of repeated thermochemical redox cycling, and the CO2 and H2 conversion extents vary depending on the metal oxide composition and experimental conditions. In this study, we developed metal oxides and simultaneously optimized experimental conditions to satisfy target CO2 and H2 conversion extents by using machine learning and Bayesian optimization. We used transfer learning to improve the prediction accuracy of the mathematical models by incorporating a data set and knowledge of oxygen vacancy formation energy. Furthermore, we analyzed the RWGS-CL reaction based on the prediction accuracy of each variable and the feature importance of the random forest regression model.

Facile Synthesis, Characterization, and Photocatalytic Activity of Hydrothermally Grown Cu2+-Doped ZnO–SnS Nanocomposites for MB Dye Degradation

The morphology, chemical composition, and doping process of metal oxides and sulfides play a significant role in their photocatalytic performance under solar light illumination. We synthesized Cu2+-doped ZnO–SnS nanocomposites at 220 °C for 10 h, using hydrothermal methods. These nanocomposites were structurally, morphologically, and optically characterized using various techniques, including powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible absorption spectroscopy. Their photocatalytic activity (PCA) on methylene blue (MB) pollutant dye was examined under 150 W solar light illumination. Mixed-phase abundances with hexagonal ZnO and orthorhombic SnS structures were observed. TEM micrographs showed changes in morphology from spherical to nano-flake structures with an increasing doping concentration. XPS indicated the chemical states of the constituent elements in the nanocomposites. UV-visible absorption spectroscopy showed a decrease in the bandgap with an increasing doping concentration. Strong PCA was observed due to the separation of charge carriers, a change in bandgap, and a high light absorption ability under solar light irradiation. The measured photodegradation efficiency of the MB dye was approximately 97% after 2 h. The movement of the charge carriers and the bandgap alignment of the synthesized composites are briefly discussed.

Synthesis and study of gas sensitive ZnFe2O4-modified ZnO nanowires

Currently, new nanostructured materials based on composite metal oxides is of great interest for the development of gas sensors with improved functional characteristics. In this work, zinc oxide nanowires were synthesized by hydrothermal method. Hierarchical ZnO/ZnFe2O4 nanostructures were obtained by immersion of zinc oxide layers in ferrous sulphate aqueous solution. The mechanism of zinc ferrite formation during the interaction of zinc oxide with iron sulphate is considered. The crystal structure of ZnO and ZnO/ZnFe2O4 were studied by Raman spectroscopy. The sensitivity of ZnO and ZnO/ZnFe2O4 nanostructures to isopropyl alcohol vapors was analyzed. It was shown that there is an optimal concentration of ferrous sulphate used to modify zinc oxide nanowires and synthesize ZnO/ZnFe2O4 composite nanostructures.

Performance of Al2O3-SiO2/PAG composite nanolubricants in automotive air-conditioning system

• Performance investigation of Al 2 O 3 -SiO 2 /PAG composite nanolubricant in AAC system. • Investigation is conducted using 60:40 ratio for up to 0.06% volume concentration. • The highest COP enhancement of 28.10% was recorded at 0.015% volume concentration. • Compressor work and power consumption were reduced to 25.26% and 19.70%, respectively. • Al 2 O 3 -SiO 2 /PAG nanolubricant at 0.015% concentration was recommended for AAC system. Automotive air-conditioning (AAC) system performance must be improved to reduce energy consumption and promote energy efficiency. Efficiency of the AAC system can be increased by applying the right lubricants. With a combination of different metal oxide components and composition ratios, composite nanolubricants are expected to outperform single-component nanolubricants in improving AAC system performance. The present work was undertaken to investigate the performance of the AAC system using combination of Al 2 O 3 -SiO 2 /PAG composite nanolubricants with composition ratio of 60:40 for 0.005 to 0.06% volume concentrations. The experiment was undertaken with an initial refrigerant charge of between 95 and 155 g and a compressor speed of between 900 and 2100 rpm. The efficiency of the AAC system was assessed by the determination of cooling capacity, compressor work, coefficient of performance (COP) and power consumption. The highest average COP enhancement was recorded 28.10% at 0.015% volume concentration. Al 2 O 3 -SiO 2 /PAG composite nanolubricants attained the highest COP value of 9.19 for 155g at compressor speed of 900 rpm. In addition, for 0.015% Al 2 O 3 -SiO 2 /PAG composite nanolubricants, the cooling capacity was enhanced up to 65.21% while the compressor work and power consumption were reduced up to 25.26% and 19.70% respectively. Therefore, 0.015% Al 2 O 3 -SiO 2 /PAG nanolubricants was highly recommended for the maximum efficiency in AAC system performance.

Hosting AlCl3 on ternary metal oxide composites for catalytic oligomerization of 1-decene: Revealing the role of supports via performance evaluation and DFT calculation

Enhancing catalytic activity and stability of supported Lewis acid catalysts remain a particular challenge owing to the limited understanding and unsatisfactory tuning of the interplay between the active components and the supports. Herein, upon immobilizing AlCl3 on a series of ternary metal oxides including La2O3–Al2O3–SiO2, NiO–Al2O3–SiO2 and Ga2O3–Al2O3–SiO2, we clearly revealed the influence of the compositions and structures of the supports on the catalyst performances through experiments together with density functional theory (DFT) calculations. The catalytic performances of the supported samples were evaluated by oligomerization of 1-decene using both batch reactor and fixed-bed apparatus. The results suggest that the AlCl3 supported by NiO–Al2O3–SiO2 composites exhibits the highest catalytic activity and stability because of its positive pore structure and thereof the high loading of active species. Importantly, DFT calculations indicate that the variations of the host-guest interaction energy between the ternary oxide composites and AlCl3 are in good agreement with the experimental results. This study highlights the compositions and structures of the supports are crucial to the catalytic performances of Lewis acid catalysts, and provides fundamental guidance for design of high-performance supported catalysts.

Facile synthesis of MgCo2O4 nanosheets and its catalysis effect on the decomposition of ammonium perchlorate

The catalysis effects of MgCo2O4 nanosheets on the thermal decomposition of ammonium perchlorate (AP) were investigated. The MgCo2O4 nanosheets were synthesized with a facile free-template hydrothermal method. The chemical structure and micromorphology of MgCo2O4 nanosheets were characterized. Moreover, the catalysis thermal decomposition properties of AP using composite metal oxides MgCo2O4 nanosheets with different amounts (1 wt%, 3 wt%, and 5 wt%) as catalysts were investigated. The results showed that the reducing decomposition temperature of AP was 155.9 °C from 431 °C to 275.1 °C with 5 wt% MgCo2O4 added. The heat release of AP was increased by 907 J/g at least. In addition, the catalysis thermal decomposition mechanism of AP with the existence of MgCo2O4 nanosheets was explained. With the increasing temperature, the accumulated electrons (e–) and holes (h+) excited were activated at the surface of MgCo2O4 nanosheets, which accelerated H transfer from H atom of NH4+ to O atom of ClO4– and boosted AP decomposition.

Fabrication of graphitic carbon nitride/ZnTi-mixed metal oxide heterostructure: Robust photocatalytic decomposition of ciprofloxacin

Photocatalytic treatment is a remarkable process that is popular for the degradation of several organic contaminants in wastewater. In this work, a series of graphitic carbon nitride/ZnTi-mixed metal oxide (CN/ZnTi-MMO) composites were prepared as photocatalysts through simple calcination. The CN-MMO samples were characterized and applied for photocatalytic degradation of ciprofloxacin (CIP), which is an antibiotic model pollutant. The optimized CN/ZnTi-MMO composite showed complete degradation of CIP within 20 min, leading to a rate constant that is approximately 6 times that of pristine CN and 7 times that of ZnTi-MMO. The increase in the degradation rate of the optimized CN/ZnTi-MMO composite was attributed to the excellent separation and transportation of photogenerated electron-holes pairs, as proven by the photoluminescence, photocurrent density, and electrochemical impedance spectroscopy results. Moreover, the energy-resolved distribution of the electron trap (ERDT) pattern of the composite sample suggests the formation of an interfacial electron trap state due to interfacial contraction in the composite, resulting in the excited electrons being trapped and avoiding charge recombination. Based on the optical properties, ERDT results, and activity test, a photocatalytic degradation mechanism of CIP over a CN/ZnTi-MMO composite was proposed. Additionally, the degraded solution showed less bio-toxicity than the original CIP solution. Thus, the CN/ZnTi-MMO composite can be employed as a potential visible-light-driven photocatalyst for the detoxification of pharmaceutical wastewater.

Electrospun Ternary Composite Metal Oxide Fibers as an Anode for Lithium-Ion Batteries

Nickel–cobalt–manganese oxides (NCMs) are widely investigated as cathode materials for lithium-ion batteries (LIBs) given their beneficial synergistic effects of high storability, electrical conductivity, and stability. However, their use as an anode for LIBs has not been adequately addressed. NCM nanofibers prepared using the multi-needle electrospinning technique are examined as the anode in LIBs. The NCM nanofibers demonstrated an initial discharge capacity of ∼1,075 mAh g−1 with an initial capacity loss of ∼42%. Through controlling the conductive additive content, the initial discharge capacity can be further improved to ∼1810 mAh g−1, mostly attributing to the improved interfiber connectivity supported by the significant lowering of impedance when the amount of conductive additive is increased. This study also reveals that the conventional ratio of 80:10:10 wt% (active materials:additives:binder) is not optimal for all samples, especially for the high active surface area electrospun nanofibers.

Cytotoxic and molecular assessment with copper and iron nanocomposite, act as a soft eradicator against cancer cells

The composites are the materials, which have either one or more combination with other material and exhibit extraordinary chemical characteristics. The present work describes the formation of composite of copper and iron metal oxide (CuFeO2). The synthesized powder materials are in nanorange. The nanocomposite nanoparticles (NCsNPs) were synthesized via solution process with using copper nitrate hexahydrate, iron nitrate non hydrate as a main precursor material whereas sodium hydroxide was utilized as a salt reducing agent. The formed NCsNPs were characterized with X-ray diffraction pattern (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Fourier Transform infra-red spectroscopy (FTIR) were used for the structural and chemical characteristic in detail. It reveals that the NCNP is ∼45 nm in size with clear spherical shaped morphology with good chemical characteristics. The NCsNPs were utilized against cancer cells (C2C12 myoblast) for to reduce the growth rate with different incubation (24 & 48 h) periods. The % cells death was examined through MTT assay at different concentration (0.5 µg/mL, 1 µg/mL, 2 µg/mL, 5 µg/mL, 10 µg/mL, 25 µg/mL, 50 µg/mL, 100 µg/mL) of NCs with different (24 & 48 h) incubations respectively. The apoptosis in cells were analyzed with quantitative polymerase chain reaction (qPCR) study with apoptotic marker gens caspase 3 and 7 with control and the obtained data reveals that with the exposure of NCs, upregulated in gene expression at fixed concentration in 24 h incubation period. Based on acquired results a possible relation between the NCs and cancer cells were also discussed.

A novel highly active catalyst form CuFeMg layered double oxides for the selective catalytic reduction of NO by CO

A series of CuxFeMg4-x-LDO and Cu/FeMg2.8-LDO catalysts were prepared by calcination of CuFeMg layered double hydroxide (LDH) for CO-SCR reaction. The Cu1.2FeMg2.8-LDO catalyst exhibited the highest CO-SCR activity and the NO conversion reach 100 % at 225–600 °C with a space velocity of 60000 mL·g−1·h−1. The CuxFeMg4-x-LDO composite metal oxide generated by topotactic transformation not only promotes the dispersion of CuO species but also promotes the generation of CuzMg1-zFe2O4 spinel phase and the reactive oxygen species (Cu2+-O-Cu2+ and Cu2+-O-Fe3+). Moreover, it also has the high H2 consumption and more surface adsorbed oxygen, which can significantly improve the redox capacity of the catalysts. The appearance of Cu+–CO/Fe2+–CO species and the relatively low activation energy are also responsible for the better catalytic activity of Cu1.2FeMg2.8-LDO at low temperatures. Furthermore, for the CO-SCR reaction over Cu1.2FeMg2.8-LDO catalysts, the L-H mechanism is consistent at low temperatures and the E-R mechanism at high temperatures. This work offers insights for the rational design of highly efficient catalysts for the low temperature CO-SCR reaction.

Fabrication of ZnAl-LDH mixed metal-oxide composites for photocatalytic degradation of 4-chlorophenol.

In this work, two different types of ZnAl-layered double hydroxide (LDH) mixed metal-oxide composites (CeO2 and SnO2) were synthesized and applied for the photodegradation of 4-chlorophenol (4-CP) in wastewater. The fabricated CeO2/ZnAl-LDH and SnO2/ZnAl-LDH were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-visible diffuse reflectance spectroscopy (UV-vis DRS), and theoretical density functional theory (DFT) calculations, suggesting that the band gaps of the synthesized hybrid composites were much lower than those of traditional ZnAl-LDH. In addition, the photocatalytic activity for 4-CP degradation and reaction kinetics were investigated to evaluate the catalytic behavior of the prepared composites. The results indicated that the photocatalytic process in this case followed a pseudo-first-order kinetic model, and SnO2/ZnAl-LDH illustrated the optimum performance for 4-CP degradation with an efficiency of 95.2% due to its stability and recyclability. Additionally, the reaction mechanism of 4-CP photodegradation was studied over SnO2/ZnAl-LDH; it presented that 4-CP could be oxidized by hydroxyl radicals, holes, and superoxide radicals, where hydroxyl radicals were identified as the dominant active species during the degradation process. Finally, decomposition intermediates were measured to deduce the reaction pathway of 4-CP, and three tentative pathways were proposed and discussed.

Different effect of Y (Y = Cu, Mn, Fe, Ni) doping on Co3O4 derived from Co-MOF for toluene catalytic destruction

A series of M−Co1Y1Ox (Y = Cu, Mn, Fe and Ni) catalysts were successfully synthesized using Y-doped Co-MOF as precursor. The introduction of different dopants greatly influenced the physicochemical properties of the obtained catalysts. Thus, resulted in different effects on toluene catalytic performance of Co3O4 derived from Co-MOF. The constructed M−Co1Cu1Ox showed an unexpected increase of the catalytic activity (T90% = 208 °C), which can be attributed to the improved physicochemical properties, such as smaller grain size, larger specific surface area, more surface defect sites, higher Co3+ and Oads, better reducibility. The results of In Situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy showed that the lattice oxygen did not participate in toluene catalytic oxidation. In addition, benzaldehyde, benzoic acid, phenol and maleate species are the major intermediates during the degradation process. This work demonstrates a facile construction method for the potential highly efficient Co-Cu composite metal oxide for toluene destruction.

Pt-Fe nanoalloy: Structure evolution study and catalytic properties in water gas shift reaction

In the present work we studied the properties of Pt0.5Cu0.5, Pt0.5Fe0.5, Pt0.33Ag0.67, Pt0.6Au0.4 nanoalloys in water gas shift (WGS) reaction for the first time. Cu, Fe, Ag, Au were chosen as modifiers due to the low catalytic activity in undesirable side reactions of carbon oxides methanation. Nanoalloys were synthesized via corresponding double complex salts decomposition, which provided the selective formation of bimetallic nanoparticles. A simulated reformate gas mixture, containing (vol.%) 10 CO, 15 CO2, 30 H2O and 45 H2, was used to evaluate the activity of these systems. Only Pt0.5Fe0.5 nanopowder was active, while Pt-FeOx metal-oxide composite was inert. The positive effect of Pt-Fe alloying on WGS performance was also confirmed for silica supported catalysts. TG and XRD in situ analysis reveal that Pt0.5Fe0.5 is stable toward oxidation under WGS reaction conditions (T < 350°C, reductive atmosphere), while Pt-FeOx undergoes partial reduction but without formation of Pt-Fe alloy nanoparticles.

Synthesis of Carbon–Metal Oxide Composites as Catalyst Supports by “Cooking Sugar with Salt”

Carbon–metal oxide composites as catalyst supports that possess unique electronic properties and synergistic effects show great promise in the area of catalysis but still remain a synthetic challenge. Here, we developed a simple and universal strategy to synthesize carbon–metal oxide composite supports by the one-step pyrolysis of carbohydrates (cyclodextrin, glucose, sucrose, and starch) and metal precursors (containing Ce, Nb, V, Zr, and Al salts). The carbohydrates with abundant hydroxyl and aldehyde groups tend to bond with metal cations to form homogeneous carbohydrate/metal ions precursors, which are then thermally converted into carbon/metal oxide composites (C–MOx) with uniformly distributed metal oxide nanoparticles. The prepared C–CeO2-supported Pt catalysts exhibit improved electrocatalytic performance for the methanol oxidation reaction, which could be ascribed to the presence of abundant Pt/CeO2 interfaces in the catalysts.

Electrode material based on reduced graphene oxide (rGO)/transition metal oxide composites for supercapacitor applications: a review

Electrode material based on reduced graphene oxide (rGO)/transition metal oxide composites for supercapacitor applications: a review

Adsorption and Catalytic Removal of Methyl Orange from Water by Functionalized Graphene Oxide Based Metal Oxide Composites

Adsorption and Catalytic Removal of Methyl Orange from Water by Functionalized Graphene Oxide Based Metal Oxide Composites

Physicochemical Properties of Organophilic Clay Developed Using Hexadecyltrimethylammonium Chloride (HDTMAC) Modifier

Aims: Ogwuta clay from Unwana in the South Eastern part of Nigeria was modified by ion exchange reaction using hexadecyltrimethylammonium chloride (HDTMAC).&#x0D; Study Design: This study was analyzed experimentally and instrumentally.&#x0D; Place and Duration of Study: This study was carried out at the Department of Pure and Industrial Chemistry, Faculty of Science, University of Port Harcourt, Nigeria. The sample collection, literature search, experiment, results and analysis lasted for one and half years.&#x0D; Methodology: Physicochemical and thermal properties of the clay were determined after modification using classical and spectroscopic techniques. A combination of the wet and dry method (X-ray Fluorescence) was used to determine the metal oxide composition. Other techniques included; Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Thermogravimetry (TG). The Cation Exchange Capacity (CEC) was determined using the methylene blue method with a value of 16.4 meq/100g after modification.&#x0D; Results: The product was slightly acidic with pH 4.3. Silica (SiO2), alumina (Al2O3), Na+, and K+ were found to be 47.58 %, 18.99%, 2.27, and 0.23% respectively. The clay was limited in mineral impurities with 0.0% T4+, 0.41% Mg2+, and 0.11% Ca2+ but high in carbonaceous matter with loss on ignition (LOI) of 13.17%. A C-H asymmetric stretching was visible around the 2931.9 cm-1 region as revealed by the Fourier Transform Infra-Red analysis. The X-Ray Diffraction analysis of the modified clay showed a basal spacing of 8.121 Å. Also, the X-Ray Diffractogram revealed kaolinite as the major clay mineral with the presence of quartz and polygorskite.&#x0D; Conclusion: This study posits that the modified clay can be potentially suitable for the adsorptive removal of organic contaminants in aqueous and real life media.