Polymetallic Oxide Research Articles

Ratiometric colorimetric detection of nitrite using CoMnO3 nanofibers as an oxidase-like enzyme to induce diazotization reaction.

Nitrite is a typical food additive and preservative used in the food industry, which has attracted considerable attention due to its severe adverse effects on human health. Herein, a sensitive and highly selective ratiometric colorimetric sensing platform for the detection of nitrite was created based on a polymetallic oxide nanozyme, CoMnO3 nanofibers (CMO) catalysis integrated with the particular diazotization reaction. The nanozyme has superior oxidase-like activity (Km was 0.105 mM and Vmax was 63.7 × 10-8 M S-1) and could catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to oxidized TMB (oxTMB), as CMO could achieve the conversion of oxygen in the solution to superoxide anion (O2˙-). In addition, it is interesting to note that oxTMB can be diazotized in the presence of nitrite under acidic conditions, causing a shift in the ratio of nitrite concentration to the absorbance peaks at 450 and 652 nm (A450/A652). The ratio of A450/A652 exhibited a positive linear relationship with the concentration of nitrite within the concentration range of 0.2-200 μM, with a detection limit of 0.094 μM. Simultaneously, this method was also successful in quantifying the nitrite produced by brined and pickled foods and the dynamic tracking of the nitrite levels in various types of dishes. The analysis method not only offers dual-signal ratio sensing with high sensitivity but also holds the benefit of outstanding selectivity for the use of the particular reaction, which has a wide range of application prospects in food safety management.

Experimental and theoretical studies of carbon monoxide oxidation over W/Cu/Ce trimetallic oxides: the effect of W addition

It is a significant method to prepare highly dispersed polymetallic oxides using in-situ doping metal organic frameworks as precursors. Herein, a series of straw-like W/Cu/Ce trimetallic oxides were prepared by using phosphotungstic ionic liquid@Ce-based metal organic framework adsorbing with copper acetylacetonate as precursors. The effect of W content on catalytic activity of W/Cu/Ce trimetallic oxides for carbon monoxide (CO) oxidation was well-investigated. Comprehensive characterization methods and density functional theory calculations were adopted to reveal the property changes of Cu/CeO2 catalyst by the addition of W. The results demonstrated that W, Cu, and Ce are highly dispersed in the prepared W/Cu/Ce trimetallic oxides, and adding proper amount of W can improve the activity of the catalyst. H2 temperature-program reduction profiles, X-ray photoelectron spectroscopy, in-situ diffuse reflectance infrared Fourier transform spectroscopy, and density functional theory calculations clearly revealed that after the addition of W, the strength of Ce-O bond is weakened, the oxygen vacancy is increased, and the adsorption of CO is enhanced, respectively, which are vital reasons for its high catalytic activity. In addition, the CO oxidation reaction pathway over prepared W/Cu/Ce trimetallic oxides based on the Mars-van Krevelen mechanism was studied, and the results exhibited that CO can wrest the lattice oxygen of W/Cu/Ce trimetallic oxides to form CO2, which is also proved to be the rate-determining step in reaction process.

NiFe2V2O8@N-Doped carbon Yolk-Double shell spheres for efficient lithium storage

Polymetallic oxide nanostructures with intricate architectures have become the promising subject of much recent investigations into high-efficiency electrode materials for lithium-ion batteries (LIBs). However, their smooth implementation is still plagued by the fabrication of multi-component structures as well as the delivered inadequate specific capacities. Here, complex NiFe2V2O8@N-doped carbon nanostructures with hierarchically porous yolk-double shell spherical architectures via a facile template-free approach are developed and evaluated as the high-efficiency anode materials for LIBs. Benefited from the yolk-double shell constructions, impressively, the electrode harvests a high reversible capacity of 1347.6 mA h g−1 over 200 cycles without visible deterioration at 0.2 A g−1, a robust rate capability (726.1 mA h g−1 at 5 A g−1), and a desirable cycle stability (75.6% capacity retention over 300 cycles at 1 A g−1). Such excellent electrochemical Li-ion storage capability is believed to result from the fast ion-diffusion kinetics enabled by the synergetic cation and oxygen redox because of the introduction of vanadium redox couples, which can be further boosted by capacitive-dominated surface electrochemical reaction. This work provides enlightening insights into the elaborate design and fabrication of complex porous yolk-shell-like nanostructures with intricate compositions for high-efficiency lithium storage.

Simple scalable preparation of SnOx/FexOy/C composite and its enhanced lithium storage

For a promisng anode material, a simple scalable preparation route is as important as its performance. Therefore, it is of great significance to develop a simple scalable preparation route for anode materials. Herein, a very simple scalable route is demonstrated to fabricate SnOx/FexOy/C composite composed of SnOx/FexOy hybrid nanoparticles embedded within an in-situ formed porous carbon matrix. Moreover, this composite has enhanced durability and kinetics during electrochemical cycling process and hence shows good performance with 628 mAh g−1 after 100 cycles at 200 mA g−1. This work may spark some inspirations to fabricate other polymetallic oxides for advanced LIB anodes.

Synthesis of the Porous ZnO Nanosheets and TiO2/ZnO/FTO Composite Films by a Low-Temperature Hydrothermal Method and Their Applications in Photocatalysis and Electrochromism

In this paper, porous zinc oxide (ZnO) nanosheets were successfully prepared by a simple low-temperature hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) tests showed that the synthesized product was ZnO with porous sheet structure. The diameter of porous nanosheets was about 100 nm and the thickness was about 8 nm. As a photocatalyst, the degradation efficiencies of porous ZnO nanosheets for methyl orange (MO), methylene blue (MB) and Rhodamine B (RhB) were 97.5%, 99% and 96.8%, respectively. In addition, the degradation efficiency of ZnO for mixed dyes (Mo, MB and RhB) was satisfactory, reaching 97.7%. The photocatalytic stability of MB was further tested and remained at 99% after 20 cycles. In the experiment, ZnO/FTO (fluorine-doped tin oxide) composites were prepared by using ZnO as the conductive layer. Titanium dioxide (TiO2) was deposited on the surface of ZnO/FTO by electrodeposition, so as to obtain a TiO2/ZnO/FTO composite. By studying the electrochromic properties of this composite, it was found that the TiO2/ZnO/FTO composite shows a large light modulation range (55% at 1000 nm) and excellent cycle stability (96.6% at 200 cycles). The main reason for the excellent electrochromic properties may be the synergistic effect between the porous structure and the polymetallic oxides. This study is helpful to improve the photocatalytic efficiency and cycling stability of metal oxides, improve the transmittance of thin films and provide a new strategy for the preparation of ZnO composite materials with excellent photocatalytic and electrochromic properties.

Efficient capture of radioactive iodine by ZIF-8 derived porous carbon

Due to the rapid diffusion of radioactive iodine, the demand for safe and efficient capture and storage of radioactive iodine is increasing worldwide. The use of porous carbon materials to capture iodine has aroused great interest. This work prepared porous carbon materials derived from polymetallic oxides of the zeolitic imidazolate framework (ZIF) by pyrolysis at 1000 °C. The carbon materials (CZIF-1000) have a high specific surface area of about 1110 m2/g and a total pore volume of 0.92 cm3/g. Adsorption studies have shown that the CZIF-1000 had significant adsorption performance for iodine, and the adsorption capacity can reach 790.8 mg/g at 8h. The potential mechanism of adsorption is that the carbonization causes the charge-transfer interaction and pore size distribution. Compared with the conventional adsorbents, the adsorbents showed faster kinetics and high extraction capacity for iodine. This experiment provides an effective method for designing a highly efficient adsorbent for iodine and broadens the ideas for developing new iodine extraction adsorbents.

Interfacial Polymetallic Oxides and Hierarchical Porous Core–Shell Fibres for High Energy‐Density Electrochemical Supercapacitors

AbstractRealizing high energy‐density and actual applications of fibre‐based electrochemical supercapacitors (FESCs) are pivotal but challenging, as the ability to construct advanced fibres for accelerating charges kinetic diffusion and Faradaic storage remain key bottlenecks. Here, we demonstrate high‐performance FESCs based on hetero‐structured polymetallic oxides/porous graphene core–sheath fibres, where the large pseudo‐active polymetallic oxide (PMO) sheath is uniformly loaded on a hierarchical porous graphene fibre (PGF) core. Due to the abundant micro‐/mesoporous pathways, large accessible surface, excellent redox activity and good interface electron conduction, the PMO‐PGF possesses high areal capacitance (2959.78 mF cm−2) and manageable Faradaic reversibility in a 6 M KOH electrolyte. Furthermore, the PMO‐PGF‐based solid‐state FESCs present high energy‐density (187.22 μ Wh cm−2), long‐life cycles (95.8 % capacitive retention after 20 000 cycles), diverse‐powered capabilities and actual energy‐supply applications.

Interfacial Polymetallic Oxides and Hierarchical Porous Core-Shell Fibres for High Energy-Density Electrochemical Supercapacitors.

Realizing high energy-density and actual applications of fibre-based electrochemical supercapacitors (FESCs) are pivotal but challenging, as the ability to construct advanced fibres for accelerating charges kinetic diffusion and Faradaic storage remain key bottlenecks. Here, we demonstrate high-performance FESCs based on hetero-structured polymetallic oxides/porous graphene core-sheath fibres, where the large pseudo-active polymetallic oxide (PMO) sheath is uniformly loaded on a hierarchical porous graphene fibre (PGF) core. Due to the abundant micro-/mesoporous pathways, large accessible surface, excellent redox activity and good interface electron conduction, the PMO-PGF possesses high areal capacitance (2959.78 mF cm-2 ) and manageable Faradaic reversibility in a 6 M KOH electrolyte. Furthermore, the PMO-PGF-based solid-state FESCs present high energy-density (187.22 μ Wh cm-2 ), long-life cycles (95.8 % capacitive retention after 20 000 cycles), diverse-powered capabilities and actual energy-supply applications.

Surface topological synthesis of polymetallic oxides coatings on lithium layered oxide for improved capacity and high-rate performance

Surface coating of lithium layered oxide cathode (e.g., LiNi0.5Co0.3Mn0.2O2, NCM532) has become an important modified method in lithium-ion batteries for pursuing higher capacity and rate performance and safety. However, the design and synthesis of polymetallic oxide (PMO) coatings on lithium layered oxide is still a challenge. Herein, polymetallic alloys (PMA) such as NiCoMn alloys (NCM), LaZrHfMo alloys (LZHM) and LaZrHfZn alloys (LZHZ) are introduced to synthesize PMO coatings on NCM532 by a surface topological conversion strategy. The advantage of this method is that numerous kinds of elements could be converted into PMO coating layer with high reaction efficiency, element universality and uniform arrangement at atomic scale. The PMO coatings modified cathodes show excellent rate performance. All of these are attributed to the fact that the PMO coating layers can effectively reduce the side reaction with electrolyte, increase the conductivity of Li+ and effectively reduce the mixing of Li+/Ni2+, maintain the stability of structure, and greatly increase the reversible capacity of NCM532. Our PMO coating strategy is also applicable to other cathode materials, such as Ni-rich and Li-rich cathode materials.

Tree-inspired efficient solar evaporation and simultaneous in-situ purification of ultra-highly concentrated mixed volatile organic wastewater

The high concentration, complexity and volatility of organic pollutants in actual wastewater are becoming major obstacles to realizing efficient water purification. Inspired by the structure and physiological process of trees, a two-in-one solar-driven evaporation/photocatalysis system for efficient water evaporation and in situ purification was fabricated from wood-derived porous carbon that was vertically aligned and uniformly loaded with polymetallic oxide nanoparticles. The system enabled rapid water evaporation (up to 3.23 kg m-2 h-1) and effective purification of mixed volatile wastewater containing rhodamine B, phenol and tetracycline with ultra-high total concentration of up to 11700 mg L-1 under 1 sun irradiation, which was significantly higher than that reported previously, and distilled water with undetected volatile pollutants could be simultaneously obtained. The combination of nanoparticles and wood hierarchical structures provided photothermal conversion substrates, catalysts and reaction/transmission channels for efficient water evaporation and in situ pollutant degradation and achieved the synergistic promotion of photothermal conversion and photo-Fenton reactions. This process provides a novel and promising strategy for the efficient treatment of highly concentrated mixed volatile organic wastewater.

Photodegradation Attenuated Oscillation:A Novel Photocatalytic Characteristic for the Polymetallic Oxide Semiconductor Porous Materials with Energy Bandgap Gradient

AbstractSamples of metal oxide SnO2 and its composite SnO2/Bi2O3, ploymetallic oxides SnO2/Bi2O3/CdO, SnO2/Bi2O3/Fe2O3, and SnO2/Bi2O3/CdO/Fe2O3 powder materials were successfully prepared by a simple solid‐state reaction method at room temperature using sodium benzenesulfonate (SBS) surfactant as template. The synthesized powder materials were characterized by X‐ray diffraction (XRD), UV‐vis diffuse reflectance spectrum (UV‐Vis), scanning electron microscopy/energy dispersive X‐ray (SEM/EDX), infrared spectroscopy (IR), X‐ray photoelectron spectroscopy (XPS), N2 adsorption‐desorption and the migration rate testing of charges. Moreover, the adsorption characteristic and photodegradation performance of methyl blue (MB, co=100 mg/L) on the materials were investigated. The results show that the degradation rate (94.2 %) of MB on the SnO2/Bi2O3/CdO/Fe2O3 nanomaterial is the highest than that of the other materials within 10 min under the visible‐light irradiation. After that, the photodegradation rate of MB on the as‐prepared SnO2/Bi2O3/CdO, SnO2/Bi2O3/Fe2O3 and SnO2/Bi2O3/CdO/Fe2O3 semiconductor materials with energy band gap gradient generates the novel phenomena of photo‐ degradation attenuated oscillation but absent for the SnO2/Bi2O3 and SnO2 materials. It may be originated from the presence of the phase‐transitions of α‐Bi2O3 and β‐Bi2O3, the change ratio of Fe3+ and Fe2+ in the photocatalytic process, and the characteristic adsorption of MB molecular groups by the different metal oxides. This provides new ideas for future inspiring continued research on this emerging class of mixed metal oxides semiconductors and thereby enables innovations.

Self-Hybrid Transition Metal Oxide Nanosheets Synthesized by a Facile Programmable and Scalable Carbonate-Template Method.

2D transition metal oxides (TMO) nanosheets have attracted considerable attention in both fundamental research and practical applications. Herein, a convenient programmable and scalable carbonate crystals templating synthesis is developed to produce high-quality self-hybrid TMO nanosheets (Si-WO3- x , Tax Oy , Mnx Oy ) and their respective polymetallic oxide hybrid nanosheets with tunable composition, low-cost and high-yield. Taking tungsten oxide nanosheets as example, silicotungstic acid precursor is in situ converted into tungsten oxide nanosheets like scales on the surface of calcium carbonate crystals through the simple soaking-drying-calcination process, and after selectively dissolving calcium carbonate by etching, the dispersive tungsten oxide nanosheets with unique self-hybrid Si-doped h-WO3 /ε-WO3 /WO2 compositions are obtained, which show excellent acetone gas-sensing performances at low temperatures. This carbonate-template method opens up the possibility to economically produce various functional TMO nanosheets with specific compositions for diverse applications.

Heterogeneous Photo-Fenton Catalytic Degradation of Practical Pharmaceutical Wastewater by Modified Attapulgite Supported Multi-Metal Oxides

Chemical synthetic pharmaceutical wastewater has characteristics of high concentration, high toxicity and poor biodegradability, so it is difficult to directly biodegrade. We used acid modified attapulgite (ATP) supported Fe-Mn-Cu polymetallic oxide as catalyst for multi-phase Fenton-like ultraviolet photocatalytic oxidation (photo-Fenton) treatment with actual chemical synthetic pharmaceutical wastewater as the treatment object. The results showed that at the initial pH of 2.0, light distance of 20 cm, and catalyst dosage and hydrogen peroxide concentration of 10.0 g/L and 0.5 mol/L respectively, the COD removal rate of wastewater reached 65% and BOD5/COD increased to 0.387 when the reaction lasted for 180 min. The results of gas chromatography-mass spectrometry (GC-MS) indicated that Fenton-like reaction with Fe-Mn-Cu@ATP had good catalytic potential and significant synergistic effect, and could remove almost all heterocycle compounds well. 3D-EEM (3D electron microscope) fluorescence spectra showed that the fluorescence intensity decreased significantly during catalytic degradation, and the UV humus-like and fulvic acid were effectively removed. The degradation efficiency of the nanocomposite only decreased by 5.8% after repeated use for 6 cycles. It seems appropriate to use this process as a pre-treatment for actual pharmaceutical wastewater to facilitate further biological treatment.

Synergistic enhancement of the oxygen evolution reaction by MoSx and sulphate on amorphous polymetallic oxide nanosheets

Amorphous polymetallic oxides containing MoSx and SO42− are proposed to enhance OER performance due to the acceleration of the *OH → *O + *H by MoSx, optimization of *OOH deprotonation by sulfate, polymetallic interaction and abundant oxygen vacancies.

Zinc-bearing ferromanganese mineralization in a rift-marginal carbonate platform, Red Sea, Egypt: Reconstruction of an epigenetic-supergenetic system

Polymetallic mineralization hosted by rift marginal carbonate preserves a comprehensive archive that enables reconstruction of the initiation and evolution of rifting. The present study focuses on a Miocene shallow marine succession and related polymetallic (Fe-Mn-Zn) ores at the Um Greifat area along the Red Sea coast in the Central Eastern Desert of Egypt. The study area represents a unique Early-Middle Miocene syntectonic marginal carbonate platform of shallow marine and coastal plain facies. The carbonate-clastic succession comprises two units, lower and upper, that are separated by a magnesite bed. Dolomitization, karstification, fracturing and brecciation are the main diagenetic features, which allow reconstructing fluctuations of sea level induced by tectonic uplift and rifting.The polymetallic nonsulfide mineralization comprises mainly Fe-Mn-Zn oxides, forming a stratiform and strata-bound ore bodies in the lower unit of the succession and/or lenticular and cavernous masses in the upper unit. The mineralogy is dominated by chalcophanite, hetaerolite, goethite, hematite and smithsonite besides zincite, pyrolusite, cryptomelane, franklinite, coronadite, quartz and alunite-natroalunite. Less common siderite, pyrite and chalcopyrite are observed. Crystal morphologies, texture and distribution of the ferromanganese minerals were modified depending on the textures, porosity, open-spaces and discontinuities of their host carbonate. The mode of occurrence, texture, mineralogy and geochemistry of the polymetallic ores suggest a two epigenetic-supergene origin. The early stage encompassed precipitation of sulfides, silica and/or circulation of highly acidic metal-rich hydrothermal solutions through faulted carbonate blocks. Dissolution and intensive oxidation of primary sulfides, Fe+2 and Mn+2 in oxic and supergenetic conditions resulted in the formation of polymetallic oxides that represent the late stage. Major uplifting and exhumation by the Red Sea extension, along with circulation of low-temperature hydrothermal fluids through faulted areas, initiated ore mineral precipitation under near-neutral to mildly acidic conditions. The interplay of diagenesis, deformation, tectonism and hydrothermalism was likely enhanced by rift-induced geothermal activity in the Red Sea basin and adjacent areas.

POM-Based MOF-Derived Co3O4/CoMoO4 Nanohybrids as Anodes for High-Performance Lithium-Ion Batteries

Polyoxometalate (POM)-based metal–organic framework (MOF)-derived Co3O4/CoMoO4 nanohybrids were successfully fabricated by a facile solvothermal method combined with a calcination process, in which a Co-based MOF, that is, ZIF-67 acts as a template while a Keggin-type POM (H3PMo12O40) serves as a compositional modulator. The materials were characterized through scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS) mapping, and electrochemical measurements. When the Co3O4/CoMoO4 nanohybrids were applied as anode materials for lithium-ion batteries (LIBs), they display large lithium storage capacity (around 900 mAh g–1 at 0.1 A g–1) and high cycling stability, and they can also exhibit good rate performances. This work might shed some light on the POM-based MOF host–guest synthesis strategy for the preparation of polymetallic oxides for enhanced electrochemical energy storage and further applications.

Surface engineering of LiNi0.8Mn0.1Co0.1O2 towards boosting lithium storage: Bimetallic oxides versus monometallic oxides

Although conventional monometallic oxide coating on lithium nickel cobalt manganese oxide (NCM) cathode materials has been extensively investigated, there are still many issues, such as low electrical conductivity, poor mechanical properties and inferior chemical stability, that need to be addressed. Indeed, because of the single nature of monometallic oxides, it is difficult to achieve the synergistic effect of various properties. In this work, NiCo 2 O 4 were rationally grown on the surface of commercial LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NCM811) to obtain a bimetallic oxide coated NCM811 as cathode material for Lithium ion batteries (LIBs). This cleverly designed coating with a higher electronic and ionic conductivity, better bulk modulus, and an outstanding interfacial stability, could improve the capacity retention to 90.97% after 200 cycles at 100 mA g −1 and enhance the initial coulombic efficiency (CE) to 82.92%. The electrochemical characterization further clarifies the indisputable benefits of NiCo 2 O 4 coating to enhancement of the cathode performance. Moreover, the theoretical calculations provide more explanations in three aspects, including mechanical stability, chemical stability and electrical properties, confirming the superiority of NiCo 2 O 4 bimetallic oxide coating with multiple properties over the monometallic one. More importantly, this study has profound implications in the design of bimetallic and polymetallic oxide coatings for electrode materials, and even other bimetallic coatings, such as sulfides and selenides, in the future. • A multi-functional bimetallic oxide coating was designed for NCM811 cathode. • Bimetallic oxide coating shows the best modification performance. • Bimetallic oxide coating balances all advantages of each monometallic oxide.

Bimetallic and Polymetallic Oxide Modification of Activated Coke by a One-Step Blending Method for Highly Efficient SO2 Removal

Bimetallic and polymetallic oxide-modified activated coke (AC) prepared by a one-step blending method and its desulfurization application were studied in this work. The bimetallic and polymetallic ...

Polymer-oriented evaporation induced self-assembly strategy to synthesize highly crystalline mesoporous metal oxides

Mesoporous metal oxides (MMOs) with high crystallinity and large surface area, as compared with its counterparts, show better performance in many applications. Current synthesis of MMOs mainly uses amphiphilic block copolymers as templates to co-assemble with metal oxide precursors. Due to the block copolymers are usually decomposed below 300 °C in air, the obtained MMOs are amorphous or semicrystalline with low thermal stability. Here, we develop a general and facile polymer-oriented evaporation induced self-assembly strategy to prepare thermostable MMOs with high crystallinity and large surface area by using metal chlorides as metal oxide precursors and cationic polymers as porogens. Our method is shown to access a library of crystalline MMOs with a range of compositions and structures including single-component MMOs, doped MMOs, multi-component MMOs, and polymetallic oxide. This approach may open up new horizons in preparing other highly crystalline mesoporous materials, such as metal phosphates, metal sulfides, metal carbide, and so on.

Solvent‐Free Self‐Assembly for Scalable Preparation of Highly Crystalline Mesoporous Metal Oxides

AbstractMesoporous metal oxides (MMOs) have been demonstrated great potential in various applications. Up to now, the direct synthesis of MMOs is still limited to the solvent induced inorganic‐organic self‐assembly process. Here, we develop a facile, general, and high throughput solvent‐free self‐assembly strategy to synthesize a series of MMOs including single‐component MMOs and multi‐component MMOs (e.g., doped MMOs, composite MMOs, and polymetallic oxide) with high crystallinity and remarkable porous properties by grinding and heating raw materials. Compared with the traditional solution self‐assembly process, the avoidance of solvents in this method not only greatly increases the yield of target products and synthesis efficiency, but also reduces the environmental pollution and the consumption of cost and energy. We believe the presented approach will pave a new avenue for scalable production of advanced mesoporous materials for various applications.