Multi-metal Oxide Research Articles

Contribution to cleaner production from the point of view of VOC emissions abatement: A review

VOC (volatile organic compounds) belong to the group of undesirable air pollutants and their industrial emissions need to be treated before venting out into the atmosphere. From various advanced technologies for VOC mitigation, catalytic oxidation technology stands out as the modern and efficient method . This review presents the recent advances in the development and usage of novel catalysts for deep catalytic oxidation from the perspective of industrial feasibility . The goal is to efficiently contribute to cleaner production and provide cost-effective VOC emissions treatment by incorporating upscaled novel catalysts into VOC abatement technology. Different washcoats and active compound mixtures are developed and tested by many research groups worldwide. Extensive state-of-the-art of experimental data (129 data samples) on preferably noble metal-based catalysts and multi-metal oxides catalysts was carried out. The data are comprehensively summarized to identify generically optimal conditions to make efficient VOC abatement industrial gas catalyst with good conversions, long-term reliability, reasonable price and realistic possibilities for upscaling. Best reported T 50 and T 90 (temperatures corresponding to 50% and 90% conversions) for toluene were 110 °C and 144 °C, for ethanol 130 °C and 155 °C and for acetone 205 °C and 236 °C, respectively. The best performing catalysts surface areas were in the range of 16–103 m 2 g −1 . Furthermore, perspectives for the future development of novel VOC catalysts are provided. Particularly, the novel field of waste-to-catalysts and structured nanocatalyst development is explored. Lastly, the issues of upscaling to pilot and full-scale for each catalytic approach were discussed. • Perspectives of novel VOC oxidation catalysts for cleaner production. • Noble metal-based and multi-metal oxides catalysts state-of-art review. • Developments in waste-derived and nano-catalyst fields. • Review of catalytic oxidation experimental data for VOC emission treatment. • Optimal catalyst properties for best price-performance.

Engineering hollow mesoporous silica supported cobalt molybdate catalyst by dissolution-regrowth strategy for efficiently aerobic oxidative desulfurization

Heterogeneous catalysts show superior separable and recyclable property in comparison with homogeneous catalysts. However, the conventional synthetic method faces the problem of uneven distribution of active sites. Here, a facile dissolution-regrowth strategy was developed to prepare hollow mesoporous silica nanospheres supported cobalt molybdate (CoMoO4/HMS) under mild conditions, simultaneously, CoMoO4 was obtained in situ. The homogenous dispersion of the active species made the catalyst manifest an outstanding desulfurization efficiency in aerobic oxidative desulfurization compared with the supported single-metal oxides catalysts or supported CoMoO4 catalyst prepared by wet impregnation. The removal efficiency of three sulfur-containing substances, such as dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene, could reach 100% by 5 h with molecular oxygen as an oxidant. Besides, the sulfur removal of DBT almost did not reduce after at least 8 cycles under the optimal reaction conditions. Through electron spin resonance spectroscopy and radical quenching experiments, O2− was determined as the main active oxygen species for sulfur oxidation. This dissolution-regrowth strategy can be used to prepare a series of supported multi-metal oxides for various applications.

Low-temperature aerobic oxidation of thiophenic sulfides over atomic Mo hosted by cobalt hydroxide sub-nanometer sheets

<h2>Summary</h2> Aerobic oxidation desulfurization (AODS) represents a carbon-neutral way to desulfurize petroleum distillates, yet it currently suffers from low efficiency and high temperature for the activation of triplet oxygen. Here, we report a sub-nanometer-thick cobalt hydroxide nanosheet that hosts an atomic molybdenum (Mo/Co(OH)₂) catalyst for the efficient aerobic oxidation of thiophenic sulfides. The catalyst achieves a turnover frequency of two orders of magnitude over that of state-of-the-art multi-metallic oxide catalysts and activates the reaction at 60°C. Coupling detailed characterizations with theoretical calculations, we formulate a descriptor—the work function of hosting materials for this reaction, which well explains the host identity dependence of the corresponding catalytic performance. We achieve the complete AODS of real diesel at 80°C under ambient pressure with negligible decay in consecutive reuses, highlighting the appealing industrial potential of our catalyst. Our findings provide fundamental and technological insights into implementing high-efficiency catalysts for the carbon-neutral AODS process.

Unravelling the chemisorption mechanism of epoxy-amine coatings on Zr-based converted galvanized steel by combined static XPS/ToF-SIMS approach

This work aims at the elucidation of the interfacial interactions established between an epoxy-amine coating and hot-dip galvanized (HDG) steel. The influence of the Zr-based conversion treatment of the substrate and the use of the Cu(II) additive on interfacial bonding is studied. To this purpose, an amine-functionalized molecule – diethylenetriamine (DETA) – is adsorbed. The complex multi-metal oxide surface of the Cu-modified Zr-based converted substrate is decomposed in derivative (simpler) systems. The resulting DETA-adsorbed model and multi-metal surfaces are investigated by X-ray photo-electron spectroscopy (XPS), and by examination of the N 1s peak, the interfacial bond density is determined. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is performed to discriminate between the different metal oxide contributions present on the substrate surface. Preferential adsorption of the DETA molecule on the zinc atoms is found on converted substrates. The interfacial bonding with the Cu cationic sites introduced by the copper additive is proven.

Highly sensitive and selective triethylamine gas sensor based on hierarchical radial CeO2/ZnO n-n heterojunction

Heterojunction formation has been considered as an effective way for exploring ultrahigh sensitive multi-metal oxide based gas sensors. Herein, unique hierarchical radial CeO2/ZnO heterostructures with excellent triethylamine (TEA) gas-sensing performance were successfully prepared via a feasible solvothermal method. The morphology, microstructure and gas-sensing performance of the composite were systematically characterized and investigated. The selective TEA gas response of the radial CeO2/ZnO heterostructure was increased by ten times as compared to that of pure ZnO phase, ascribing to the abundant reactive sites induced by the formation of n-n heterojunction. Furthermore, the radial CeO2/ZnO n-n heterojunction exhibited the best TEA gas sensitivity with Ra/Rg = 92.17 at an operating temperature of 200 °C, a fast response/recovery time of 29 s/23 s, and a long-term stable repeatability for at least 60 days. The excellent selectivity of CeO2/ZnO heterojunction for TEA sensing is also remained even when mixing with other interferent gases. The interface-dependent and enhanced TEA sensing property of CeO2/ZnO can be ascribed to its intriguing radial morphology, for which the CeO2 nanoparticles located in the internal structure of the composite while the ZnO hexagonal prism grew radially outward. The well assembled hierarchical CeO2/ZnO n-n heterojunction with abundant accessible active sites significantly facilitate the surface reaction and diffusion of target gas molecules at the interface between CeO2 and ZnO during gas sensing process.

Structural, optical and electrical study of new polycrystalline Bi1.5-xCexSb1.5CuO7 solid solution fractions with pyrochlore-type structure

This study is a contribution to the development of novel materials based on transition multi metal oxides, which can be applied as photocatalysts or solid electrolytes in solid fuel cells. A new pyrochlore-like solid solution fractions with general chemical formula Bi1.5−xCexSb1.5CuO7 was synthetized and characterized using solid-state reaction and characterized by X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrical resistivity measurements and solid-state ultraviolet–visible spectroscopy (UV–Vis). The XRDP analysis revealed a high purity pyrochlore-like structure of the solid solution fractions, this being primary with cerium saturation between x=0.2. and x=0.4. A significant decrease of the refined cubic cell parameter was observed, in accordance with the size difference between bismuth and cerium cations. Also, a drastic drop off in electrical resistivity was observed at x=0.4. Besides, the core level X-ray photoelectron spectroscopy technique clearly detected the presence of all elements involved in the composition of these materials, and proved the simultaneous trivalent and tetravalent oxidation states of incorporated cerium. Furthermore, secondary and back-scattered electrons scanning electron microscopy analysis allowed the monitoring of the grain size as well as the phase inhomogeneity of the solid solution fractions. Finally, it was thus found that the optical band gap energy of the solid solution fractions was about 1.8 ​eV.

Atomic Structure Modification of Fe‒N‒C Catalysts via Morphology Engineering of Graphene for Enhanced Conversion Kinetics of Lithium–Sulfur Batteries (Adv. Funct. Mater. 19/2022)

Multi-Metal Oxide Nanoparticles Multi-metal oxide (MMO) nanomaterials have significant potential to facilitate various demanding (electro)catalytic reactions, but its intrinsic complexity hinders the in-depth understanding of the origin of the catalytic activity. In article number 2110857, Seoin Back, Seung-Ho Yu, Yung-Eun Sung, Taeghwan Hyeon, and co-workers report the structural understanding of uniform-sized spinel-type MMO nanoparticles, which boosts the electrocatalytic oxygen reduction reaction (ORR) activity. Physicochemical and electrochemical analyses reveal the contribution of each element to the structural flexibility and corresponding improved ORR activity.

Polyoxovanadates as Precursors for the Synthesis of Colloidal Multi-Metal Oxide Nanocrystals

Polyoxovanadates as Precursors for the Synthesis of Colloidal Multi-Metal Oxide Nanocrystals

Front Cover: Crystal Structures of Iron‐Based Oxides and Their Catalytic Efficiencies for the Oxygen Evolution Reaction: A Trend in Alkaline Media (ChemElectroChem 9/2022)

The Front Cover illustrates that artificial intelligence facilitates the understanding of science in electrocatalysis on heterogeneous crystalline compounds. Machine learning method demonstrates that alkaline oxygen evolution reaction on iron-based multimetal oxides is uniquely controlled by a structural descriptor, Fe–O bond length, and the trend is generally applicable regardless of chemical compositions, valence states of iron and structural categories of the crystals. More information can be found in the Research Article by Y. Sugawara et al.

Crystal Structures of Iron‐Based Oxides and Their Catalytic Efficiencies for the Oxygen Evolution Reaction: A Trend in Alkaline Media

AbstractThe physical and chemical properties of inorganic materials significantly depend on their crystal structures. Therefore, precise design of structures can promote the development of highly active electrocatalysts. Due to the present environmental issues, it is desirable to establish a structural factor that regulates the anodic oxygen evolution reaction (OER) in water splitting. Herein, we demonstrate structural descriptors using nine kinds of unreported iron‐based multimetal oxides with complicated structures and 15 kinds of previously reported iron‐based oxides. Density functional theory simulations find that their OER activities cannot be explained by the electronic descriptor, i. e., charge‐transfer energy. In contrast, the OER activities exhibit clear correlations with structural descriptors. To objectively determine the most dominant structural descriptor for OER electrocatalysis on iron‐based oxides, data‐driven machine learning (ML) is exploited. Thus, ML analysis reveals that Fe−O bond length is the most dominant structural descriptor for electrocatalytic OER on iron‐based oxides.

Different La/Fe oxide composites for efficient phosphate removal from wastewater: Properties and mechanisms

Metal oxides are widely used in the removal of oxygen-containing anions from the aqueous phase, and multi-metallic oxides were promising adsorbents for removal performance. In order to explore the effect of different La/Fe oxide composites (LF) on phosphate adsorption, three bimetallic composite oxides of La/Fe were prepared by citric acid sol-gel method at 600, 700 and 800 oC (named LF-600, LF-700 and LF-800). According to adsorption experiments, the adsorption capacity was changed obviously with the temperature increasing. The maximum adsorption capacity was 77.08, 41.17 and 14.58 mg g−1 at pH 7.0 of LF-600, LF-700 and LF-800, respectively. The specific surface area (SBET) and the crystal type are the main factors affecting the adsorption capacity. With the temperature increasing, the SBET reduced and the crystal phase was LaOCl and Fe2O3 of LF-600, LaOCl, LaFeO3 and Fe2O3 of LF-700, and LaFeO3 and LaOCl of LF-800. In addition, the adsorption capacities decreased obviously with the increase of pH and the addition of CO32−. The FTIR, XRD and XPS analysis proved that the adsorption mechanism mainly was surface precipitation, electrostatic attraction and complexation, and complexation was the main adsorption mechanism.

Structural Insights into Multi‐Metal Spinel Oxide Nanoparticles for Boosting Oxygen Reduction Electrocatalysis (Adv. Mater. 8/2022)

Multi-Metal Oxide (Electro)catalysts Multi-metal oxide (MMO) nanomaterials have significant potential to facilitate various demanding (electro)catalytic reactions, but their intrinsic complexity hinders in-depth understanding of the origin of the catalytic activity. In article number 2107868, Kug-Seung Lee, Seoin Back, Yung-Eun Sung, Taeghwan Hyeon, and co-workers develop a structural understanding of uniform-sized spinel-type MMO nanoparticles, which boosts the electrocatalytic oxygen reduction reaction (ORR) activity. Physicochemical and electrochemical analysis reveal the contribution of each element to the structural flexibility and corresponding improved ORR activity.

Morphology-controllable synthesis of hierarchical hollow GaFeO3 microcubes with selective triethylamine gas-sensing properties

Hierarchical multi-metal oxide-based gas sensors with high surface area and abundant active sites have attracted intensely research interests for their highly sensitive and fast gas detection performance. Developing synthetic strategies for obtaining novel hierarchical metal oxides with high sensing performance remains eminently challenging. Herein, hierarchial hollow GaFeO3 microcubes were successfully prepared via a Ga3+-modified Fe-based Prussian Blue (PB) mediated template conversion strategy. The microsized morphologies and hollow interior structures of GaFeO3 microcubes can be feasibly modulated by controlling the thermolysis temperatures. The ultrasmall nanoparticle-assembly of GaFeO3 architecture obtained at 500 °C exhibited an optimum response value (Ra/Rg) of 7.4, and rapid response/recovery times (9 s/49 s) toward 200 ppm triethylamine (TEA) at a working temperature of 200 °C, as well as remarkable selectivity and excellent long-term stability (for at least 31 days), which are intrinsically beneficial from the unique interior loose structure with good permeability for diffusion of target gases. This work provides a promising approach for synthesizing various hierarchical multimetal oxides with intriguing nanoparticle-assembled hollow structure and broad prospects for practical gas sensing applications.

Pre-coagulated landfill leachate treatment by Electro-oxidation using MMO/Ti, Pt/Ti, and graphite anodes

In this study, sequential coagulation and electro-oxidation (EO) processes were applied to landfill leachate, which is highly contaminated and complex wastewater. Since the pollutant content of the leachate was too high, the coagulation process (poly aluminum chloride (PAC) as a coagulant) was applied as a pre-treatment to reduce the cost of the EO process. The Box-Behnken design of response surface methodology was used. The color number (CN) removal efficiency estimated by the model under optimum operating conditions was 80.1%, while it was 77.6% in the experimental studies performed under optimum conditions to verify the model conformity. Multi-metal oxide doped Ti (MMO/Ti), Pt doped Ti (Pt/Ti), and graphite were used as anode and stainless steel was used as cathode in the EO process. In the EO process in which Pt/Ti anode was used, chemical oxygen demand (COD), UV254, and CN removal efficiencies were 52.8, 68.1, and 85.6%, respectively under the conditions of applied current 1.25 A and the pH 5. The CN value decreased to 4.2 after the coagulation process and it was 0.6 at the effluent of the EO process.

Metal-Organic Frameworks Derived Interfacing Fe2o3/Znco2o4 Multimetal Oxides as a Bifunctional Electrocatalyst for Overall Water Splitting

Metal-Organic Frameworks Derived Interfacing Fe2o3/Znco2o4 Multimetal Oxides as a Bifunctional Electrocatalyst for Overall Water Splitting

Construction of vertically aligned Ni-Co-Mo hybrid oxides nanosheet array for high-performance hybrid supercapacitors

Multi-metal oxide materials have gained increasing attention due to their superior electrochemical performance for supercapacitors. In this work, Ni-Co-Mo oxides composite materials (NiCoMo/NF) are synthesized and anchored on Ni foam in the form of vertically aligned nanosheet arrays using a two-step hydrothermal method. It has confirmed that good electrochemical performance stems from a synergic interaction effect between the hybrid Ni-Co-Mo composite materials and the co-existence of Ni-Co and Co-Mo oxide, which can be attributed to a unique nanostructure in the hybrid Ni-Co-Mo composite materials and Ni-Co/Co-Mo oxide intersections with each other. The NiCoMo/NF binder-free electrode shows an enhanced specific capacitance of 1837.7 F g−1(3.31 F cm−2) at a current density of 1 A g−1 and maintains capacitance retention of 81.2% after 6000 cycles at 5 A g−1. Meanwhile, the fabricated hybrid capacitor achieves high specific energy of 41.1 W h kg−1. The results indicate that NiCoMo/NF has the potential for application in supercapacitors. Moreover, our work provides a practical approach for fabrication of multi-metal oxide materials and hold promise for high-power energy storage devices.

Fabrication of a Mesoporous Multimetallic Oxide-based Ion-Sensitive Field Effect Transistor for pH Sensing.

Sensitive and reliable noninvasive sensors are in demand to cope with an increasing need for robust working conditions and fast results. One of the leading potential technologies is field-effect transistor (FET)-based sensors to improve response time, sensitivity, and stability. Here, a sol–gel method fabricates an ion-sensitive field-effect transistor with a high current and output sensitivity for electrochemical sensing, solving binary device design, component regulating, and long-term stability, while maintaining the promoted sensitivity. Metal oxide-based devices with single and binary contents are fabricated and characterized for monitoring pH changes, with performance fitted to a Nernst–Poisson model. After detecting the performance, the result was compared with devices in different components and ratios to obtain excellent performance and high stability. In addition, these extended gate FETs with multimetallic oxide promise efficiency and stability optimization in terms of a flexible component design, demonstrating the feasibility of the novel sol–gel fabrication method to achieve efficient and reliable FET sensors.

Hierarchical α-Fe2O3/MnO2/rGO ternary composites as an electrode material for high performance supercapacitors application

Transition Metal oxide decorated graphene nanosheets have accumulated a lot of consideration due to their potential applications in electrochemical energy storage devices especially in supercapacitors (SCs). Nanostructured mixed multi-metal oxides have been employed as promising electrodes for creating more active site for electron transfer. All-solid-state asymmetric supercapacitors (ASC) have significant theoretical capacitance, good rate capability, and excellent cycling stability suitable for energy storage device fabrication with optimum energy and power density. Here, we demonstrate a Solvothermal route to synthesis ternary α-Fe2O3/MnO2/rGO composites.. The hybrid ternary composites in 3-electrode configuration showed maximum capacitance of 447 F g−1 at optimum current density at1A g−1 and 96 % of capacitance retention after 10,000 GCD cycles at 10 A g−1in an alkaline medium. The fabricated ASC device with ternary composites (positive) and negative electrodes (rGO) separated by PVA/KOH gel-electrolyte separator exhibits maximum cell voltage of 1.4 V with high specific capacitance of 97 F g−1 at 1 A g−1. Additionally, the assembled device delivered a high energy density of 13.2 W h kg−1and a high power density of 6124 W kg−1 with an excellent capacitance retention of 92% and columbic efficiency of 96 % preserved over 5000 cycles at 10 A g−1with good reversibility. Besides, the Solvothermal strategy supports for the fabrication of metal oxide could be applicable for other metal oxide electrode materials preparation.

Cover Feature: Comprehensive Structural Descriptor for Electrocatalytic Oxygen Evolution Activities of Iron Oxides (ChemElectroChem 23/2021)

The Cover Feature illustrates the unveiled structural descriptor for electrocatalysis on Fe-based oxides. Shorter Fe−O bond length is more beneficial for the electrocatalytic oxygen evolution reaction. The descriptor is applicable to a wide range of Fe-based multimetal oxides regardless of chemical compositions. More information can be found in the Article by Y. Sugawara et al.

Rational Design of a Two-Dimensional Janus CuFeO2+δ Single Layer as a Photocatalyst and Photoelectrode.

The exfoliation of 2D nanomaterials from 3D multimetal oxides with a stable structure is a great challenge. Herein, a delafossite CuFeO2+δ nanosheet becomes an open-layered structure by introducing excess oxygen so that the 2D Janus CuFeO2+δ single layer can be further obtained by aqueous ultrasonic exfoliation. The 2D Janus CuFeO2+δ single layer breaks the limitation of mirror symmetry, which is very beneficial to the effective separation of photogenerated electron-hole pairs. Serving as both a photoelectrode and a photocatalyst, the 2D Janus CuFeO2+δ single layer/few layer remarkably enhances the photocatalytic activity with long-term stability: the photocurrent density is increased by 2-fold, and the rate of H2 evolution is increased by 1.5-fold, in comparison with the counterpart of unexfoliated CuFeO2+δ nanosheets. This work demonstrates that 2D nanomaterials can be directly exfoliated from 3D nanomaterials by rational composition and microstructure design, which is helpful in promoting the development of bimetallic-oxide-ene (BMOene) as a novel functional material.