Multi-metal Oxide Research Articles

Design and Synthesis of Mn-Fe-Cu Multi-Metal Oxide Catalysts for Efficient Degradation of Organic Pollutants

ABSTRACT Heterogeneous ozone-catalyzed oxidation technology is one of the effective ways of wastewater treatment, and the development of efficient ozone oxidation catalyst is the key to this process. Herein, this work proposes the design and synthesis of an efficient multi-metal composite oxide catalyst by metal salt precursor mixing-direct granulation. The successful loading of the main active metal components, such as Mn, Cu, Fe, etc. was clarified by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and other systematic characterizations, the specific surface area of the catalyst spheres produced by pelletizing could reach 231.699 m2/g, and the pore volume was 0.414 cm3/g. And after the optimization of the catalyst preparation conditions and oxidation process conditions, the removal rate of COD could reach more than 50% for the simulated wastewater, and the catalytic activity was basically kept stable in a long-cycle operation of 1000 h, which indicated that the prepared multi-metal composite oxide catalyst had good catalytic activity and stability. Finally, the EPR characterization clarified that the degradation of organic pollutants in the catalytic process was mainly dominated by the singlet oxygen and proposed a possible catalytic oxidation mechanism, which provided a reference for the synthesis of new high-efficiency ozone oxidation catalysts.

Designing Sustainable Electrocatalysts for Electrolysis By Structural Modifications of Multi-Metal Oxides

Innovations in materials are essential to advances in electrolysis reactions. In particular, the development of sustainable electrocatalysts based on earth-abundant elements can pave the way for significant progress in this field. We have designed several series of highly active electrocatalysts based on multi-metal oxides, comprising earth-abundant metals, specifically materials with perovskite-type structures. Importantly, we have shown that targeted modification of structural properties can be used as a tool for tuning the electrocatalytic performance. To showcase the systematic improvement in the activity of these electrocatalysts, we have demonstrated their activity toward both anodic and cathodic half-reactions of water electrolysis. These studies have shown that a gradual increase in structural order can lead to a systematic enhancement of electrocatalytic properties, as evident from low overpotentials, enhanced kinetics of the electrolysis reaction, and high stability of electrocatalysts. In addition, we have investigated the role of oxygen-vacancies in the new multi-metal oxide electrocatalysts, indicating that the concentration and arrangement of vacancies has a major impact on electrocatalytic properties. Importantly, these catalysts are highly stable and retain their activity and structural integrity over many hours of electrochemical operation, as shown by chronopotentiometry, as well as X-ray diffraction and X-ray photoelectron spectroscopy before and after the electrolysis process. The ability to tune the electrocatalytic activity by controlling the structural properties of earth-abundant catalysts can lead to significant advances in the efficiency and sustainability of electrolysis reactions.

Aqueous Solution-Gel Synthesis of Copper-Based Ternary Oxides As Efficient Photocathodes in Photoelectrochemical Cells

The efficient valorization of solar energy will be vital for sustainable energy and fuel production while mitigating atmospheric pollution. Photoelectrochemical (PEC) systems present a promising avenue for converting light into chemical energy, by using semiconducting photoanodes and/or -cathodes to initiate redox reactions via electron-hole pair generation. The choice of semiconductor materials plays a critical role in PEC performance, requiring materials that meet specific criteria such as efficient absorption of visible light, composition of earth-abundant elements, and stability in aqueous solutions under irradiation. CuO and Cu2O have attracted attention because their appropriate band edges are favorable to both photo-electrochemical water splitting and CO2 conversion, alongside their reasonable abundance and low toxicity. However, substantial photocorrosion limits their functionality as photo-electrodes, motivating the exploration of copper-based ternary oxides, which exhibit greater stability under operating conditions. [1]With over 60 elements available for potential photo-electrode compositions, a comprehensive and accessible synthesis method would be valuable for identifying suitable photoactive materials. Here, the citrate-based aqueous solution-gel method emerges as a versatile strategy for formulating stable aqueous metal ion precursor solutions, facilitating the synthesis of (doped) multi-metal oxides. [2] Nonetheless, achieving phase-pure copper-based ternary oxides presents challenges due to copper's distinctive redox chemistry. This study focuses on synthesizing copper-based photocathode materials, specifically copper bismuth oxide (CBO), copper ferrite (CFO), and copper niobate (CNO). The formulation of precursor solutions and their thermal processing are highlighted. Thin-film photocathodes are deposited on transparent conductive substrates via spin coating. The phase purity of resulting copper-based oxides is assessed using X-ray diffraction and Raman spectroscopy, while UV-Vis spectroscopy is used to determine their optical bandgap. Furthermore, the photocathodes are subjected to linear sweep voltammetry in both dark and illuminated conditions to evaluate their photoelectrochemical performance.The aqueous solution-gel method enables the deposition of various functional oxide coatings as photocathodes, allowing for the optimization of coating thickness and phase purity. [3] Interestingly, this approach can also be used to establish a non-stoichiometric gradient in the coatings, which is demonstrated to enhance electron-hole separation. Additionally, the solution-gel deposition of a suitable hole transfer layer improves the overall PEC performance even further. These observations emphasize the importance of combining materials design and innovative synthesis strategies for exploring efficient photoactive materials and optimizing device architectures.[1] Wang et al. “Insights into the development of Cu-based photocathodes for carbon dioxide conversion” Green Chem. (2021) 23, 3207[2] Van Bael et al. “Aqueous Precursor Systems” in “Chemical Solution Deposition of Functional Oxide Thin Films” Schneller, T., Waser, R., Kosec, M., Payne, D. (eds) 2013, Springer, Vienna.[3] Joos et al. “Facile Aqueous Solution-Gel route toward Thin Film CuBi2O4 Photocathodes for Solar Hydrogen Production” Advanced Sustainable Systems (2023) 7, 2300083 This work has received financial support from the European Fund for Regional Development through the Interreg Vlaanderen-Nederland project FOTON, from the Belgian federal government through the ETF project T-REX, from the Flemish government under the program ‘Vlaamse Veerkracht’ and from the VLAIO network “Flanders Innovation & Entrepreneurship” through the Catalisti Moonshot project SYN-CAT.

Efficient Oxygen Evolution Activity of Nickel-Based Compounds and Their Structural and Electronic Effects

Present global energy issues have prompted demand for the actualization of carbon neutral by the establishment of hydrogen society. Green hydrogen production through anion-exchange membrane water electrolysis using renewable energy-derived electricity is a promising process because inexpensive nonprecious metal-based electrocatalysts can be used in alkaline media. However, oxygen evolution reaction (OER) at the anode side in the water electrolysis is sluggish; thus, the development of highly active electrocatalysts bearing nonprecious metals for OER is considerably desirable.Recently, we have intensively researched the OER activity of iron-based oxides and developed outstanding iron-based multimetal oxides using our proposed descriptors in terms of atomic configurations.[1–3] Furthermore, we have expanded our research on OER electrocatalysts to iron-based phosphates and reported that electrodes made by iron-based phosphates overcame those of the most active iron-based multimetal oxides and IrO2.[4] To further enhance the OER efficiency, we focused on nickel-based compounds. Nickel intrinsically catalyzes OER efficiently compared to other nonprecious transition metals.[5] In this study, we investigate the OER activity trend in Ni-based compounds and clarify the main factor to determine their OER activity. Remarkably, the OER activity exhibited a clear correlation with metal−oxygen bond length in their crystals, i.e., shorter metal−oxygen bond lengths are more beneficial for the OER, which shows a good agreement to the findings in the case of iron-based oxides, as displayed in Figure 1a.[1,2] Additionally, the plots for nickel-based compounds in Figure 1a are located at higher OER activities than those for the iron-based oxides. This trend demonstrated an improvement of OER efficiency on nickel compared to iron. Furthermore, to get insights into electronic effects on the activity, we analyzed electronic states of the nickel-based oxides by density functional theory (DFT) calculations. The DFT calculations revealed that the OER activities were linearly correlated with the level of their occupied Ni 3d orbitals, as shown in Figure 1b; i.e., the upshifted Ni 3d orbital strengthened interaction with nickel active site and Oxygen intermediates and boosted their OER activities. Thus, the electronic states of nickel-based compounds were reflected in metal−oxygen bond length and intrinsically determined the OER activity. This study provided a useful design guideline to improve nickel-based OER electrocatalysts and contributed to the innovation of green hydrogen production.[6] The part of this paper is based on results obtained from a project, JPNP14021, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Electron-Delocalization Across High Surface Entropy Sub-1nm Nanobelts Toward Enhanced Electrocatalytic Urea Oxidation.

Integration of inherently incompatible elements into a single sublattice, resulting in the formation of monophasic metal oxide, holds great scientific promise; it unveils that the overlooked surface entropy in subnanometer materials can thermodynamically facilitate the formation of homogeneous single-phase structures. Here a facile approach is proposed for synthesizing multimetallic oxide subnanometer nanobelts (MMO-PMA SNBs) by harnessing the potential of phosphomolybdic acid (PMA) clusters to capture inorganic nuclei and inhibiting their subsequent growth in solvothermal reactions. Experimental and theoretical analyses show that PMA in MMO-PMA SNBs not only aids subnanometer structure formation but also induces in situ modifications to catalytic sites. The electron transfer from PMA, coupled with the loss of elemental identity of transition metals, leads to electron delocalization, jointly activating the reaction sites. The unique structure makes pentametallic oxide (PMO-PMA SNBs) achieve a current density of 10mAcm-2 at a low potential of 1.34V and remain stable for 24 h at 10mA cm-2 on urea oxidation reaction (UOR). The exceptional UOR catalytic activity suggests a potential for utilizing multimetallic subnanometer nanostructures in energy conversion and environmental remediation.

Quasi-1D Oxides as Electrocatalysts for Water-Splitting: Case Study of Sr9M2Mn5O21 (M = Co, Ni, Cu, Zn).

We have demonstrated that multimetal oxides with a quasi-1D structure can be effective electrocatalysts for water electrolysis. Four materials have been systematically investigated, namely, Sr9Co2Mn5O21, Sr9Ni2Mn5O21, Sr9Cu2Mn5O21, and Sr9Zn2Mn5O21, comprising 1D chains of face-sharing MnO6 octahedra and MO6 trigonal prisms (M = Co, Ni, Cu or Zn), which are held together by strontium ions located between the chains. These materials show a consistent trend in electrocatalytic properties for both half-reactions of water-splitting, i.e., oxygen evolution and hydrogen evolution reactions (OER and HER). In particular, Sr9Ni2Mn5O21 has an outstanding performance for OER, with an overpotential of 0.37 V, which is lower than those of many 3D and 2D oxides, and rivals the activity of noble metal catalysts, such as RuO2. This is important given that the OER is considered the bottleneck of the water-slitting process. Chronopotentiometry studies, combined with X-ray photoelectron spectroscopy (XPS) and X-ray diffraction experiments pre- and post-reaction, indicate that Sr9Ni2Mn5O21 is highly stable and retains its structural integrity upon electrocatalytic reactions. This study highlights the potential of quasi-1D oxides as active electrocatalysts for water-splitting.

Effect of mixed metal ions and incorporation of activated carbon on the physiochemical and catalytic properties of spinel based (Ni,Fe)Co2O4@C nanoparticles

The challenge of producing cost-effective oxygen electrocatalysts for the oxygen reduction reaction (ORR) continues to impede the advancement of fuel cell technology. Herein, we report the effect of Ni and activated carbon on mixed metal (Ni,Fe)Co2O4 and (Ni,Fe)Co2O4@C spinel oxide nanoparticles synthesized by facile and versatile co-precipitation method followed by the physio-chemical, morphological properties and electrochemical analysis towards oxygen reduction reaction. The formation of FeCo2O4, (Ni,Fe)Co2O4 and (Ni,Fe)Co2O4@C nanoparticles was confirmed with X-ray diffraction and Raman analysis while D and G band revealed the presence of carbon in the (Ni,Fe)Co2O4@C nanoparticles. The Brunauer–Emmett–Teller analysis reveals the mesoporous behaviour of the synthesized multi-metal oxide nanoparticles. X-ray photoelectron spectroscopy analysis reveals the presence of Co3+/Co2+, Fe3+/Fe2+, Ni3+/Ni2+, O1s and C1s confirms the formation of complex (Fe3+Co2+)(Ni2+Ni3+Fe2+Fe3+Co3+)2O4 spinel structure. The ionic radii of the Co, Fe and Ni ions plays a vital role in the formation of complex spinel structures. The ORR analysis was studied by electrochemical analysis and observed (Ni,Fe)Co2O4 outperformed FeCo2O4 in terms of onset potential and current densities for the ORR. (Ni,Fe)Co2O4@C exhibited the highest catalytic activity with −2.18 mAcm−2 at 0.1 V vs RHE, which is relatively comparable with that of commercial Pt/C. Furthermore, the electrocatalytic analysis revealed the ORR mechanism adheres to the direct "4e−" process. The intermetallic interactions between the Co, Fe and Ni ions along with high crystallinity, significant surface area, high porosity, and the influence of carbon incorporation that are all contribute to the improved electrocatalytic activity of the cobalite-based multi-metal spinel oxides.

Synthesis and characterization of multi metal oxide nanocomposite (SrO–NiO) for photodetector applications

Synthesis and characterization of multi metal oxide nanocomposite (SrO–NiO) for photodetector applications

Improvement of Electrochemical Performance of Lithium-Ion Anode Materials by Local Oxidation of Multivalent Metal Oxides (CoO)

Improvement of Electrochemical Performance of Lithium-Ion Anode Materials by Local Oxidation of Multivalent Metal Oxides (CoO)

CO2‐Hydrogenation to Methanol over CuO/ZnO Based Infiltration Composite Catalyst Spheres

AbstractMultiple active component catalysts for efficient conversion of CO2 to Methanol (MeOH) are synthesized through coating γ‐Al2O3 carrier spheres by incipient wetness impregnation method (IWI). The well‐known bimetallic Copper Oxide/Zinc Oxide (CuO/ZnO)is promoted in three steps, first by Cerium Oxide (CeO2), then additionally with Zirconium Oxide (ZrO2) and finally with Calcium Oxide (CaO) resulting in four carrier catalysts with high surface area and catalyst pore volume. Quaternary and quinary carrier catalysts promoted with moderate CeO2, ZrO2 in the quaternary (20 % CZCZ) and additionally with CaO (20 % CZCZC) in the quinary catalysts demonstrate high CO2‐conversion ratios (16.2 % and 18.7 %) and space time yields (0.51 and 0.47 gMeOH h−1 gCatalyst−1) at 5 MPa and 250 °C. The high conversion ratios (XCO2) and good methanol space‐time‐yields (STYMeOH) are attributed to enhanced copper dispersion and several multi metal oxide component interactions essential to enhance CO2‐activation and ‐conversion through the catalytic systems as well as very high overall surface area. Compared to related studies, the carrier catalysts show superior conversion rates, proving the effectiveness of the introduced multi‐component carrier catalyst and extending the understanding of infiltrate composites as possible large‐scale application alternatives to precipitated MeOH catalyst systems.

Using the High-Entropy Approach to Obtain Multimetal Oxide Nanozymes: Library Synthesis, In Silico Structure-Activity, and Immunoassay Performance.

High-entropy nanomaterials exhibit exceptional mechanical, physical, and chemical properties, finding applications in many industries. Peroxidases are metalloenzymes that accelerate the decomposition of hydrogen peroxide. This study uses the high-entropy approach to generate multimetal oxide-based nanozymes with peroxidase-like activity and explores their application as sensors in ex vivo bioassays. A library of 81 materials was produced using a coprecipitation method for rapid synthesis of up to 100 variants in a single plate. The A and B sites of the magnetite structure, (AA')(BB'B'')2O4, were substituted with up to six different cations (Cu/Fe/Zn/Mg/Mn/Cr). Increasing the compositional complexity improved the catalytic performance; however, substitutions of single elements also caused drastic reductions in the peroxidase-like activity. A generalized linear model was developed describing the relationship between material composition and catalytic activity. Binary interactions between elements that acted synergistically or antagonistically were identified, and a single parameter, the mean interaction effect, was observed to correlate highly with catalytic activity, providing a valuable tool for the design of high-entropy-inspired nanozymes.

Hollow CuCo-based trimetallic oxides derived from ZIF-67 as enhanced electrocatalysts for OER

Multimetallic oxide configuration and hollow structure construction are effective strategies for the design of efficient electrocatalysts, which can regulate the intrinsic properties of the active sites, enlarge the specific surface areas and expose more active sites. In this work, hollow-structured CuCo-based ternary metal oxides supported nitrogen-carbon networks (HS-CuMCoOx, M = Fe/Zn/Ni) derived from ZIF-67 hollow spheres were fabricated through facile ion exchange and heat treatment. The prepared composites possess hollow configurations with homogeneously dispersed trimetallic active species on the shells. Among all the ternary metallic derivatives, hollow spheres supporting Cu, Fe, and Co oxides (HS-CuFeCoOx) exhibited highest electrocatalytic activity towards oxygen evolution reaction (OER). The improved OER performance ascribed to the inherent electrocatalytic properties of the ternary metal active species and microstructure by hollow structure design and heat treatment, which offered an effective synthetic strategy for the fabrication of trimetallic oxide composites for as OER electrocatalysts.

High Entropy Spinel Oxide (AlCrCoNiFe2)O as Highly Active Oxygen Evolution Reaction Catalysts.

The advancement of water electrolyzer technologies and the production of sustainable hydrogen fuel heavily rely on the development of efficient and cost-effective electrocatalysts for the oxygen evolution reaction (OER). High entropy ceramics, characterized by their unique properties, such as lattice distortion and high configurational entropy, hold significant promise for catalytic applications. In this study, we utilized the sol-gel autocombustion method to synthesize high entropy ceramics containing a combination of 3d transition metals and aluminum ((AlCrCoNiFe2)O). We then compared their electrocatalytic performance with other series of synthesized multimetal and monometallic oxides for the OER under alkaline conditions. Our electrochemical analysis revealed that the high entropy ceramics exhibited excellent performance and the lowest charge transfer resistance, Tafel slope (29 mV·dec-1), and overpotential (η10 = 230 mV). These remarkable results can be primarily attributed to the high entropy effect induced by the addition of Al, Cr, Co, Ni, and Fe, which introduces increased disorder and complexity into the material's structure. This, in turn, facilitates more efficient OER catalysis by providing diverse active sites and promoting optimal electronic configurations for the reaction. Furthermore, the strong electronic interactions among the constituent elements in the metallic spinels further enhance their catalytic activity in the initiation of the OER process. Combined with the reduced charge transfer resistance, these factors collectively play pivotal roles in enhancing the OER performance of the electrocatalysts. Overall, our study provides valuable insights into the design and development of high-performance electrocatalysts for sustainable energy applications. By harnessing the high entropy effect and leveraging strong electronic interactions, electrocatalytic materials can be tailored to improve efficiency and stability, thus advancing the progress of clean energy technologies.

Flexible bifunctional wood-derived water filtration/photo-Fenton membrane for efficient purification of mixed organic wastewater

Membrane filtration technology demonstrates excellent continuous processing capability in organic wastewater treated processes, which is usually applied in continuous industrial processes. However, it still faces a contradiction between membrane flux and treatment efficiency. In this study, a flexible wood-based photocatalytic membrane with high membrane flux and exceptional photofenton performance was developed via partial fragment wood components and uniform loading of multi-metal oxide nanocatalysts, which breaks mentioned contradiction. The homogeneous and efficient wood-based dual-function water filtration/photofenton system was established by leveraging the directional porous structure of wood in conjunction with the nanocatalysts while adjusting their ratios, enabling effective purification of highly concentrated mixed organic wastewater. Under one solar intensity and negative pressure filtration (0.03 MPa), the system treated a mixed solution containing Rhodamine B, phenol, and tetracycline at a concentration of 280 mg L−1 with the removal efficiencies of 100 %, 93.4 %, and 90.2 %, respectively, and the membrane flux could up to 315.3 Lm−2 h−1 within one hour. The membrane showed a good recycling performance, and the decay rates were all below 5 % after five cycles. This wood-based dual-function water filtration/photo-Fenton system provides a new approach for the continuous dynamic treatment of high-concentration organic wastewater on an industrial scale.

Transition metal oxides in CO2 driven oxidative dehydrogenation: Uncovering their redox properties

Extensive research efforts have been devoted to using greenhouse gas CO2 in upgrading bio-derived feedstock to value-added chemicals using the oxidative dehydrogenation route (CO2-ODH) with low-energy input. To realize the effective deployment of CO2-ODH at an industrial scale, it is imperative to advance the development of robust catalysts that can selectively catalyze C-H over C-C bonds, while simultaneously demonstrating thermodynamic stability to coke formation or sintering. Transition metal-based catalysts exhibit significant potential for being highly selective and reactive in the simultaneous conversion of CO2 and hydrocarbons, owing to their surface reducibility, well-balanced acid/base properties, and dynamic oxygen storage capacity. To stimulate further optimization, it's crucial to discover key design principles, potential trends and descriptors, and effective strategies to fine-tune the catalyst materials. This review comprehensively examines experimental and theoretical research aimed at pinpointing the key catalytic characteristics that affect selectivity in transition metal-based mono, bi, and multimetal oxides. It covers aspects like combinations of active metals and supports, effects of composition and alloying, interfacial structures, adsorption strengths, dynamics of in-situ restructuring, defect creation, surface morphology, and electronic properties, among others. We wrap up by suggesting approaches to overcome present obstacles in catalyst design and reactor technology, potentially bridging the lab-to-industry gap in this domain.

Metal-Organic-Framework Derived Co-Mo Multimetal Oxide Semiconductors: Selective Trace-Level Hydrogen Sulfide Detection.

The development of a highly selective and trace-level gas sensing platform for detecting hydrogen sulfide (H2S) remains a formidable challenge. To solve this problem, Co-Mo multimetal oxide semiconductors are rationally tailored by employing metal organic frameworks (MOFs) as self-sacrificial templates. The MOF-derived Co3O4/β-CoMoO4 based gas sensors displays high sensitivity (Rg/Ra = 22) to 10 ppm of H2S and ultralow limit of detection (10 ppb H2S). The formation of p-p heterojunction and multivalence states of Mo play a crucial role in electron transfer and oxygen adsorption. A sensor array constructed from four Co3O4/β-CoMoO4 materials with different Co/Mo ratios demonstrates a superior selective discrimination of H2S from other VOCs and malodorous gases by principal component analysis (PCA). Besides, a H2S gas sensing and alarming platform was designed for monitoring the environment contaminated with H2S. This finding provides a feasible approach for the discovery of highly efficient gas sensors to monitor environmental H2S concentration.

Enhancing Lithium-Ion Diffusion Kinetics in a 3D Lithium Metal Host through Surface Modification with Hierarchical Multimetal Oxides.

Lithium metal is a promising anode candidate to achieve high-energy-density lithium metal batteries (LMBs) due to its ultrahigh theoretical capacity (3860 mA h g-1) and low electrochemical potential (-3.04 V vs S.H.E). Unfortunately, the commercialization of lithium metal anodes is hindered by the growth of Li dendrites and the infinite Li volume changes during the cycling process. Herein, we introduce a 3D hierarchical multimetal oxide nanowire framework as a current collector for Li metal anodes. The hierarchical metal oxide layers of CoO and CuxO provide abundant Li nucleation sites and thus offer uniform Li plating and regulate Li nucleation during the charge/discharge process. As a result, half cells present a prolonging Coulombic efficiency of 97% at 1 mA cm-2 with a capacity of 1 mA h cm-2 for over 300 cycles. A stable cyclability of symmetric cells is demonstrated under 1 mA cm-2 with a capacity of 1 mA h cm-2 for 1500 h. Full cells paired with an LFP cathode show a stable capacity of 131.5 mA h g-1 with a capacity retention of 92% for 200 cycles. These results will shed insights into the design of 3D Cu current collectors for high-performance composite Li metal anodes.

Improving the Rechargeable Li-CO2 Battery Performances by Tailoring Oxygen Defects on Li-Ni-Co-Mn Multi-Metal Oxide Catalysts Recycled from Spent Ternary Lithium-Ion Batteries.

Rechargeable Li-CO2 batteries are considered as a promising carbon-neutral energy storage technology owing to their ultra-high energy density and efficient CO2 capture capability. However, the sluggish CO2 reduction/evolution kinetics impedes their practical application, which leads to huge overpotentials and poor cyclability. Multi-element transit metal oxides (TMOs) are demonstrated as effective cathodic catalysts for Li-CO2 batteries. But there are no reports on the integration of defect engineering on multi-element TMOs. Herein, the oxygen vacancy-bearing Li-Ni-Co-Mn multi-oxide (Re-NCM-H3) catalyst with the α-NaFeO2-type structure is first fabricated by annealing the NiCoMn precursor that derived from spent ternary LiNi0.8Co0.1Mn0.1O2 cathode, in H2 at 300°C. As demonstrated by experimental results and theory calculations, the introduction of moderate oxygen vacancy has optimized electronic state near the Fermi level (Ef), eventually improving CO2 adsorption and charge transfer. Therefore, the Li-CO2 batteries with Re-NCM-H3 catalyst deliver a high capacity (11808.9 mAh g-1), a lower overpotential (1.54V), as well as excellent stability over 216 cycles at 100mA g-1 and 165 cycles at 400mA g-1. This study not only opens up a sustainable application of spent ternary cathode, but also validates the potential of multi-element TMO catalysts with oxygen defects for high-efficiency Li-CO2 batteries.

Highly sensitive and label-free detection of naproxen using mixed metal oxide-based field effect transistor as a biosensor for in-vitro analysis of urine

Naproxen (Nap) is a nonsteroidal anti-inflammatory drug widely prescribed for treating fever, inflammation, and pain due to its easy absorption. Considering the side effects of long-term use of Nap and the risk of environmental pollution as a precursor, it is necessary to measure its concentration. ISFET-based sensors are very attractive tools for monitoring small amounts of analytes in biological samples. On the other hand, stabilizing nanocomposites with Nap oxidation capability provides an electrochemical signal for quantification. In this study, ISFET was used for comparative analysis of Nap concentration employing CeO2/CuO/MnO, CeO2/CuO/NiO multi-metal oxides, and La-doped CoFe layered double hydroxide (LDH) as sensing layers for the first time. The detection limits of the mentioned layers were 14.08 μM, 11.15 μM, and 19.11 μM, respectively, and the method was used to detect Nap in urine with a linear range of 0–400 μM. Compared to other methods, the proposed ISFET-based sensor for Nap detection has the capability of miniaturization, low sample amount, real-time measurement, low electrical power requirement, reusability, and high stability.

Morphostructural studies of pure and mixed metal oxide nanoparticles of Cu with Ni and Zn

Nano-scale interactions between pure metal or metal-oxide components within an oxide matrix can improve functional performance over basic metal oxides. This study reports on the synthesis of monometallic (CuO), bimetallic (CuO–NiO) and trimetallic (CuO–NiO–ZnO) oxide nanoparticles (NPs) via the co-precipitation method and investigation of morphostructural properties. All of the synthesized metal oxide NPs were calcined at 550 °C temperature and annealed under vacuum. In this work, we applied Scherrer formula, modified Scherrer equation, Williamson-Hall plots, and Halder-Wagner plots to calculate the average crystallite size. The XRD data analysis showed that average crystallite sizes of the as-synthesized metal oxide phases were between 4 nm and 76 nm and average diameters calculated from SEM image were between 15 nm and 83 nm. The XRD studies also disclosed that average crystallite size and lattice microstrain of the CuO phases remain almost same (43 nm–46 nm and 2.074×10−3 to 2.665×10−3) for pure CuO and mixed CuO–NiO; but in case of mixed CuO–NiO–ZnO it is found to decrease in size to 11 nm where lattice microstrain increases to 9.653×10−3. Line broadening of diffraction peaks from microstrain contribution was between 0.02 and 0.01. Degree of crystallinity (%) of CuO phases found to decrease from 81 to 71. Dislocation density of CuO phases found to increase from 6.63×10−4nm−2 to 12.68×10−3nm−2. X-ray density of CuO phases increased from 6.48 to 6.53 g/cm3. Where this calculated small dislocation density well agreed with the high crystallinity. Crystal structure and specific surface area were determined from lattice constants and X-ray density. These synthesized nanopowders showed the existence of monoclinic, cubic, and hexagonal phases. The obtained NPs of multi-metal oxide explained more than one phases with different size, shape, and morphology at nano scale.