Metal Oxide Composites Research Articles

Inside Ceramics and Between MgO Grains: Solid-State Synthesis of Intergranular Semiconducting or Magnetic Spinels.

Configurations of composite metal oxide nanoparticles are typically far off their thermodynamic equilibrium state. As such they represent a versatile but so far overlooked source material for the intergranular solid-state chemistry inside ceramics. Here, it is demonstrated how the admixture of Fe3+ and In3+ ions to MgO nanoparticles, as achieved by flame spray pyrolysis, can be used to engage ion exsolution, phase separation, and subsequent spinel formation inside the network of diamagnetic and insulating MgO grains. Extremely high uniformity in the distribution of intergranular ferrimagnetic MgFe2O4 films and grains with resulting magnetic coercivity values that depend on the nanoparticles' initial Fe3+ concentration is achieved. Moreover, percolating networks of semiconducting MgIn2O4 are derived from MgO nanoparticles with admixtures of 20 at% In3+ that gives rise to an enhancement of dc conductivity values by more than five orders of magnitude in comparison to the insulating MgO host. The here presented approach is general and applicable to the synthesis of a variety of functional spinel nanostructures embedded inside ceramic matrices. Nanoparticle loading with aliovalent impurity ions, the level of nanoparticle powder density after compaction, and sintering temperature are key parameters for this novel type of solid-state chemistry in between the host grains.

Photodegradation stability of marine coatings derived from PVC binder loaded with composite metal oxides particles

Photodegradation stability of marine coatings derived from PVC binder loaded with composite metal oxides particles

A Critical Review of the Synthesis and Applications of Spinel-Derived Catalysts to Bio-Oil Upgrading.

The transformation of renewable bio-oil into platform chemicals and bio-oil through catalytic processes embodies an efficient approach within the realm of advancing sustainable energy. Spinel-based catalysts have garnered significant attention owing to their ability to precisely tune metals within the framework, facilitating adjustments to structural, physical, and electronic properties, coupled with their remarkable thermal stability. This review aims to provide a comprehensive overview of recent advancements in spinel-based catalysts for upgrading bio-oil. Its objective is to shed light on their potential to address the limitations of conventional catalysts. Initially, a comprehensive analysis is conducted on different metal oxide composites in terms of their similarity and dissimilarity on properties. Subsequently, the synthesis methodologies are scrutinised and potential avenues for their modification are explored. Following this, an in-depth discussion ensues regarding the spinels ascatalysts or catalyst precursors for catalytic cracking, ketonisation, catalytic hydrodeoxygenation, steam and aqueous-phase reforming, andelectrocatalytic upgrading of bio-oil. Finally, the challenges and potential prospectsare addressed, with a specific focus on the machine learning - based approaches to optimise the structure and activity of spinel catalysts. This review aims to provide specific directions for further exploration and maximisation of the spinel catalysts in the bio-oil upgrading field.

Incorporation of Mg/Al metal oxide into ionic liquids for CO2 capture and conversion into cyclic carbonate under solvent-free conditions: effect of coordination ability, recyclability, and catalytic study

The direct conversion of carbon dioxide (CO2) and propylene oxide (PO) into propylene carbonate (PC) offers a green way to utilize anthropogenic CO2. However, this reaction is limited by low conversion of PO and harsh reaction conditions. In this study, we solve this problem using ionic liquids (ILs)/metal oxide composites (ILs@MAO). The catalytic activity of MAO-500 (500 = annealing temperature) is poor evidenced by its low conversion of PO (24.94%). However, ILs@MAO-500 has a high conversion of PO (97.54%) under similar reaction conditions (2 h at 1.5 MPa CO2 pressure, 90 oC, and 0.85 g catalyst). The ILs consist of imidazolium cation with weak coordinated [NTf2]- anion leading to outward movement of anion resulting in the formation of “heterodinuclear complex”. This complex generates an amorphous-crystalline intermediate with balanced acid-base sites that activate PO and stabilize the catalytic intermediate. The high PO conversion is theorized to be primarily due to in large part the abundant reactive sites in the ILs that are covalently immobilized on the MAO-500 carrier. Furthermore, even after multiple recycling, ILs@MAO-500 remains stable and exhibits high yield and selectivity. The proposed solvent-free catalytic system is mild, kinetically fast, and naturally safe for coupling CO2 and PO into PC synthesis.

Wet-chemical preparation and physicochemical characterization of nanostructured Zn-Bi2O3/CeO2 composite: A visible-light-driven catalyst for the annihilation of pharmaceutical pollutant

A modified co-precipitation technique assisted with cetyltrimethylammonium bromide (CTAB) surfactant was used to synthesize a nanostructured and zinc-doped mixed metal oxide (Zn-Bi2O3/CeO2) composite. Using X-ray diffraction (XRD), the synthesized nanocomposite was studied in terms of its crystal structure, grain size, percentage crystallinity, and percentage porosity. Energy dispersive X-ray elemental analysis (EDX) was used to ascertain the chemical composition, SEM to confirm the creation of nanostructure material, and Fourier transform infrared spectroscopy (FTIR) to extract the existing functional groups. Investigation of light harvesting properties (UV/Vis) and thermogravimetric analysis (TGA) reveals that the doped composite exhibits a band gap driven by visible light and remarkable thermal stability at high temperatures. The pH value at which a material's net charge is zero, known as pHpzc, is 7.93 for the doped mixed metal oxide composite. The Zn-Bi2O3/CeO2 nanocomposite effectively eliminates 98.4 percent of the quinolone antibiotic (levofloxacin) via a mechanism that integrates sorption and photocatalytic degradation induced by visible light. To determine the optimal circumstances for the efficient operation of a photocatalyst, we experimented with different time intervals, beginning drug concentrations, catalyst dosages, operating temperatures, and pH levels. Reusability tests and post-activity FTIR analysis were used to investigate the long-term usability and structural stability of the newly developed doped composite photocatalyst. The scavenging tests revealed a potential photocatalytic mechanism to explain the annihilation of the levofloxacin drug on the synthesized catalyst. The physicochemical and photocatalytic evaluations recommend that the assembled integrated material has excellent potential for mineralizing medicinal products in pharmaceutical wastes.

Construction of the Co3O4/Nb2O5 Composite Catalyst with a Prickly Spherelike Architecture for CO2 Cycloaddition with Styrene Oxide.

A high-performance Nb2O5-based catalyst for the cycloaddition of CO2 with SO is designed by properly unifying the concepts of compositional regulation and architectural engineering. The Co3O4/Nb2O5 composite catalyst shows an intriguing prickly spherelike morphology. It exhibits a high styrene carbonate (SC) yield of 94.3% within 4 h (0.0824 mol g-1 h-1) under mild reaction conditions (0.4 MPa of CO2 and a reaction temperature of 90 °C) assisted by tetrabutylammonium bromide (TBAB). The coupling of Co3O4, which chemically interacts with Nb2O5, can effectively modulate the electronic structures of Nb2O5, constructing abundant acid/base sites for effectively activating the reactants and boosting the intrinsic activity. The high activity, cost-effectiveness, and good recyclability make the tailor-made Co3O4/Nb2O5 prickly spheres more appealing for commercial applications. This work offers new insights into designing and constructing well-integrated metal oxide composites for the cycloaddition of CO2 with an epoxide.

Electroplating sludge derived CuFe2O4/MgFe2O4 metal oxide composites for highly efficient removal of Congo red.

The utilization of electroplating sludge (ES) to derive metal oxide functional materials is a key strategy, as it enables the recycling of valuable elements, mitigates environmental risks, and aligns with green, low-carbon development strategies. Nevertheless, the development of metal oxide composite functional materials with distinctive structures and properties derived from ES continues to present several challenges. Herein, we synthesized CuFe2O4/MgFe2O4 metal oxide composites from ES by one-step hydrothermal method. As-obtained CuFe2O4/MgFe2O4 metal oxide composites (MMOs) have a unique layered structure, richer mesoporous and microporous structures, activity sites. When evaluated as an adsorbent for Congo red (CR), as-synthesized CuFe2O4/MgFe2O4 with layered structure composite exhibited excellent adsorption capacity (1039.1 mg/g) and reusability (85.55% after five cycles), which was superior to most similar adsorbents reported till date. Such improvement is explored to mainly originate from two respects: the physical adsorption facilitated by the abundant pores formed through the stacking and growth of CuFe2O4 and MgFe2O4, and the chemisorption resulting from surface complexation and hydrogen bonding between the MMOs and CR. This strategy to directly transform ES into functional materials shows great promise both in waste management and preparation of robust adsorbents for wastewater treatment.

Enhancing hydrogen storage properties of MgH2 via reaction-induced construction of Ti/Co/Mn-based multiphase catalytic system

The inherent kinetic limitations and high operating temperatures of magnesium hydride (MgH2) hinder its practical applications. Herein, we report the successful synthesis of a TiO2@MnCo2O4.5 composite transition metal oxide catalyst and investigate its effect on the hydrogen storage performance of MgH2. TiO2@MnCo2O4.5 exhibits exceptional catalytic activity in the hydrogen dissociation and recombination reactions of during absorption and desorption processes, reducing the dehydrogenation activation energy of MgH2 to 75.54 kJ/mol. Notably, the MgH2-6 wt% TiO2@MnCo2O4.5 system releases 6.04 wt% H2 within 30 min at 250 °C, and 4.98 wt% H2 within 120 min at 225 °C. Furthermore, it can absorb 5.08 wt% H2 within 3 min at 150 °C and achieve a hydrogen absorption capacity of 2.02 wt% within 30 min even at 30 °C. The reaction-induced decomposition and phase transformation of TiO2@MnCo2O4.5 create a multiphase, multi-site catalytic environment. The hydrogen storage system based on the coexistence of Mg6MnO8, Mn, Ti2O3, and CoO features abundant diffusion pathways and nucleation sites, playing a critical role in suppressing the energy barriers for MgH2 hydrogen absorption and desorption reactions. These findings provide a meaningful theoretical foundation for the microstructural optimization and performance regulation of Mg-based hydrogen storage materials.

Thermally Stable Pt Clusters Anchored on Mg–Al–Ti Composite Metal Oxide for Efficient Cycloalkane Dehydrogenation

Thermally Stable Pt Clusters Anchored on Mg–Al–Ti Composite Metal Oxide for Efficient Cycloalkane Dehydrogenation

Preparation of nano SnO2-Sb2O3 composite electrode by cathodic deposition for the elimination of phenol by Sonoelectrochemical oxidation

Abstract The preparation of composite metal oxide to attain high efficiency in removing phenol from wastewater has a great concern. In the present study, the focus would be on adopting antimony-tin oxide coating onto graphite substrates instead of titanium; besides the effect of SbCl3 concentration on the SnO2-Sb2O3 composite would be examined. The performance of this composite electrode as the working electrode in the removal of phenol by sonoelectrochemical oxidation will be studied. The antimony-tin dioxide composite electrode was prepared by cathodic deposition with SnCl2 . 2H2O solution in a mixture of HNO3 and NaNO3, with different concentrations of SbCl3. The SnO2-Sb2O3 deposit layer’s structure and morphology were examined and the 4 g/l SbCl3 gave the more crystallized with nanoscale electrodeposition. The highest removal of phenol was 100% at a temperature of 30 oC, with a current density (CD) of 25 mA/cm2.

Synthesis and Characterization of Polyaniline/CuO Nanocomposites with Various Temperature

Polyaniline (PANI) metal oxide composites are known for their high electrical conductivity, environmental stability, and enhanced mechanical strength, making them valuable in applications such as sensors, batteries, and electromagnetic shielding. This study focuses on synthesizing and characterizing PANI/CuO nanocomposites to examine their structural, morphological, and functional properties at different synthesis temperatures. By integrating the conductive polymer PANI with copper oxide (CuO), a p-type semiconductor with a narrow band gap, the material’s capabilities are significantly enhanced. The oxidative polymerization of aniline, the process by which PANI is formed, requires precise control of oxidizing agents and reaction conditions, as these factors directly affect the polymerization, conductivity, and overall properties of the resulting nanocomposite. The PANI/CuO nanocomposites were synthesized at three different temperatures: 10℃, 25℃, and 50℃, to determine how temperature affects their characteristics. Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM) were employed to analyze these nanocomposites. FTIR results revealed shifts in the quinoid and benzenoid rings, indicating hydrogen bonding between the NH group of PANI and the CuO surface, which accelerates charge transfer. The SEM analysis showed that while pure PANI exhibits a uniform globular morphology, the PANI/CuO nanocomposites display a nanorod morphology. These morphological differences impact the surface area and electrical conductivity of the composites, highlighting the significance of temperature in tailoring the material's properties for specific applications.

Synergistically enhanced photocatalytic properties of Co3O4-G/GO nanocomposites: unravelling their interactions and charge-transfer dynamics using XAS.

Metal oxide composites with graphene/graphene oxide have increasingly gained popularity in enhancing the photocatalytic degradation of several existing harmful dyes. Moreover, identifying the role of carbon networks and their interactions in composite formation would assist in the design and development of photocatalysts. In the present study, we investigated the role of carbon networks in improving photocatalytic properties. Electronic structure analysis of cobalt oxide-graphene (C2)/graphene oxide (C3) nanocomposites using XAS suggested possible charge transfer from cobalt oxide nanoparticles to the carbon network during composite formation. The photocatalytic degradation of C3 towards phenol dye (1×10-3M) was >50% and improved the degradation rate with k = 0.231 h-1.In the quest to understand the mechanism unfolding on its surface, in situ XAS under UV-visible irradiation was performed, which shed light on delayed excitonic recombination in the synthesized nanocomposites. This enabled hydroxy radicals (˙OH) to play a preeminent role in the cleavage of the phenol ring and its intermediaries. Based on these observations, a detailed mechanism for charge transfer occurring during nanocomposite formation and the mechanism involved in the enhanced photocatalytic activity of the nanocomposite photocatalyst towards phenol degradation under the influence of UV-visible irradiation are discussed.

Hydrogen Production from Ammonia Decomposition: A Mini-Review of Metal Oxide-Based Catalysts.

Efficient hydrogen storage and transportation are crucial for the sustainable development of human society. Ammonia, with a hydrogen storage density of up to 17.6 wt%, is considered an ideal energy carrier for large-scale hydrogen storage and has great potential for development and application in the "hydrogen economy". However, achieving ammonia decomposition to hydrogen under mild conditions is challenging, and therefore, the development of suitable catalysts is essential. Metal oxide-based catalysts are commonly used in the industry. This paper presents a comprehensive review of single and composite metal oxide catalysts for ammonia decomposition catalysis. The focus is on analyzing the conformational relationships and interactions between metal oxide carriers and active metal sites. The aim is to develop new and efficient metal oxide-based catalysts for large-scale green ammonia decomposition.

(Invited) Triboelectricity Based Self-Powered Sensing Towards Ecological Protection and Health Monitoring

In recent years, the necessity for the evolution of effective research approaches to develop self-powered sensing networks has gained significant attention in view of their importance as the element of Internet of Things (IoTs) in the present scenario of global energy crisis and ecological dilemma. In these circumstances, triboelectric nanogenerators (TENGs) manifest remarkable potentiality and versatility in the eco-friendly approaches of self-powered sensing, considering their appreciable sensitivity to the environmental and applied conditions. By harvesting wasted energy, the triboelectricity based self-powered sensing networks exhibit promising prospect to be applicable in ecological protection and smart health monitoring by rapid detection of chronic diseases, as an effective step towards the wellbeing of human health and environment synchronically. In this talk, I will represent novel mechanisms for implementing the TENGs based on nano/micro-structured tribo-materials comprising polymer/semiconducting metal oxide composites and problematic waste materials into self-powered ultra-broadband photodetection, toxic gas sensing and early detection of chronic disease for the human health and environmental safety. This novel method for the instantaneous response of the triboelectric signals to the biomarker for specific disease provides a prospective framework for painless, rapid, very cost-efficient, and eco-friendly disease detection, which is anticipated to be widely preferred as more advantageous than some traditional methods owing to the convenience of both the patients and medical professionals. Additionally, the approach of reusing the problematic waste materials in these TENG devices presents an effective step towards the circular economy, in light of the environmental pillar of ESG (Environmental, Social & Governance).

Electrochemical-based amine functionalized gold nanoparticles decorated on nanosheets for normetanephrine detection in plasma and serum

Metals and metal oxide composites are prominent materials for detecting biomolecules in body fluids through electrochemical methods. In this study, iron-cobalt nanosheets (FeCoNS) decorated with glucosamine-functionalized gold nanoparticles (Gln-AuNPs) were synthesized to detect normetanephrine (NMN) in human plasma and serum samples. The morphology and chemical composition of the Gln-AuNPs@FeCoNS were analyzed via high-resolution transmission electron microscopy, field-emission scanning electron microscopy, atomic force microscopy, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. A glassy carbon electrode (GCE) was modified with Gln-AuNPs@FeCoNS, exhibiting high electrochemical activity for determining NMN in phosphate buffer saline (PBS) and in real samples. Importantly, the increase in the oxidation current during the reaction between the GCE modified with Gln-AuNPs@FeCoNS and NMN enabled the detection and quantification of NMN. Cyclic voltammetry, differential pulse voltammetry, and amperometry (i-t) were used to assess the sensing performance of the GCE modified with Gln-AuNPs@FeCoNS. The fabricated sensor was highly sensitive toward NMN, with a limit of detection of 0.066, 0.085, and 0.7 µM in PBS, plasma, and serum samples, respectively. The proposed electrochemical sensor provides a new platform for utilizing active metal-based catalysts to detect various biomolecules.

Bi2WO6 and TiS2 composite nanostructures displaying synergetic boosted energy storage in supercapacitor

The enhancement in the capacitance of a supercapacitor has been successfully achieved by synthesizing Bi2WO6 (BW), TiS2 (T), and Bi2WO6/TiS2 (BW/T) composites utilizing the hydrothermal process. The possible growth mechanism has also been presented. The morphological and structural characteristics of the cultivated samples were observed using FT-IR, XRD, SEM, EDS, and UV–vis spectroscopy techniques. TiS2 nano platelets uniformly dispersed across the hierarchically opened surface of Bi2WO6 in the synthesized hierarchical composite. This leads to an increase in surface porosity and surface area, which in turn enhances the transport of electrons and ions on the composite BW/T surface. The optimal electrode BW/T@40 % composite electrode shown a substantial enhancement in particular capacitance (1153.3 F/g) compared to the separate BW (523.7 F/g) and T (453.3 F/g) electrodes due to its rapid ion transfer, many active sites on its large surface area, and strong synergistic impact. Furthermore, the BW/T@40 % combination demonstrated exceptional stability, with over 92 % of its capacitance maintained after 4500th cycles and b value (0.71) proved the supercapacitor behavior. Therefore, BW/T@40 % binary metal oxide and sulfide composites exhibit improved specific capacitance and greatly prolonged life-cycle, confirming its potential use in high-performance energy storage devices.

Highly Stable MOFs-Derived Cu–Co Composite Metal Oxides for Catalytic Oxidation of Toluene

CuCoOx was prepared by in situ pyrolysis of Cu2+ partially substituted MOF-74 precursor with Co-MOF as a template for catalytic oxidation of toluene. T90 (the temperature corresponding conversion of 90%) was only 212°C, at 1000 ppm toluene and weight hourly space velocity (WHSV) of 36 000 mL g–1 h–1. In addition, the conversion was maintained above 97% for 74 h of continuous reaction at 260°C. Even if after 2400 ppm 1,2-dichloroethane (1,2-DCE) poisoning for 2 h, the toluene conversion was still up to 93%, demonstrating excellent stability and resistance to deactivation of catalyst. Furthermore, The high activity and stability of CuCoOx could be attributed to the large specific surface area as well as the high Co2+/Co3+, Cu2+/Cu+, and Olatt/Oads molar ratios.

MXenes and their composites for advanced cathodes in multivalent ion batteries

In recent years, multivalent metal-ion batteries (MMIBs) have garnered significant attention and research interest because of their abundant natural reserves, low cost, and high safety. However, in practical applications, owing to the high charge density of multivalent metal ions and the strong interaction between the intercalated metal ion and the cathode, the cathode exhibits low capacity and poor cycle stability. Therefore, it is crucial to explore suitable cathode materials for use in MMIBs. MXenes are novel two-dimensional materials that have developed rapidly in the field of energy storage. The current use of MXenes as cathodes in MMIBs has not yet been systematically summarized. This review summarizes the evolution and achievements of MXene-based cathodes in MMIBs, including MXenes and their derivatives, MXene/transition metal oxide composites, MXene/sulfur-based material composites, MXene/selenium-based material composites, and other MXene composites. Finally, the current challenges and future development of MXenes for advanced cathodes in MMIBs are discussed.

Stability, thermophysical properties, forced convective heat transfer, entropy minimization and exergy performance of a novel hybrid nanofluid: Experimental study

This research explores how incorporating graphene oxide (GO) into red mud (RM) creates a superior nanomaterial for heat transfer applications. RM's inherent stability and thermal conductivity (TC), stemming from its metal oxide composition, are further amplified by this hybrid nano-composite. The study primarily investigates the thermal performance of water-based RM mono nanofluid and hybrid RM + GO (50:50) nanofluids (HNFs) at nanoparticle concentrations of 0.1–0.75 vol%. An experimental setup consisting of a copper tube under turbulent flow conditions with a constant heat flux and a bulk fluid temperature of 60 °C was used to test the performance of HNF. Various techniques are used to characterize the nanoparticles (NPs), and evaluate the thermophysical properties of nanofluids. The experimental data reveal that the heat transfer coefficient (HTC) increases with higher inlet fluid velocity and nanoparticle concentrations. Notably, the HNF demonstrates a significant improvement of 47.2 % in Nusselt number (Nu) and a 13.6 % rise in pressure drop (Δp) compared to base fluid, at 0.75 vol%. The least entropy generation number (EGN) is obtained for the HNF (0.0049) compared to the RM NF (0.00583) at a concentration of 0.75 vol%. The exergy efficiency improves with an increase in concentration and Reynolds number (Re). Additionally, the study identifies the performance index (PI) of NFs and modelled correlations for estimating the Nu and friction factor (f) within the investigated concentration range.

One-step formation of synergistic ZnO/SnO2 composite nanostructures derived from annealing of crystalline ZnSn(OH)6 nanocubes for enhanced catalytic degradation of organic pollutants

Binary metal oxides/hydroxides derived primary metal oxide composites have a pivotal role in diverse applications because of the beneficial interfacial contact, good synergism, high porous nature, and high stability. The current work deals with the derived ZnO/SnO2 composite nanostructures from post-annealing crystalline ZnSn(OH)6 (ZTO-RT) nanocubes, initially synthesized via a single-step hydrothermal synthesis method. First, the pristine ZTO-RT is synthesized @ 180 °C in a hydrothermal autoclave. Further, the transformation of ZTO-RT to ZnO/SnO2 composite nanostructures is performed at two different annealing temperatures of 500 °C (ZTO-DV-500) and 750 °C (ZTO-DV-750) in the vacuum. The respective samples' physical characterization was studied and compared using various analytical techniques. The X-ray diffraction analysis affirms the amorphous nature of ZTO-DV-500 and the poly-crystalline nature of ZTO-DV-750. The nanocube morphologies of the samples are retained even at high-temperature sintering. The existence of metal-oxygen bonds on the surface of the ZnO/SnO2 composite is sustained by X-ray photoelectron spectroscopy. ZTO-DV-750 has larger pores (pore volume - 0.091 cm3 g−1) than the ZTO-DV-500 (0.051 cm3 g−1). In the presence of NaBH4 aqueous solution, the enhanced rhodamine B dye degradations of ZTO-DV-750 are observed. At low RhB concentrations (5 mg L−1), the ZTO-DV-500 and ZTO-DV-750 rate constants are determined to be 0.099 and 0.156 min−1, respectively, while at high concentration (10 mg L−1), these values are 0.043, and 0.091 min−1. Therefore, the ZTO-DV-750 composite has shown potent catalytic activity with NaBH4 over ZTO-DV-500 to decolourise organic dyes.