Single Oxides Research Articles

Magnesium-Modified Co3O4 Catalyst with Remarkable Performance for Toluene Low Temperature Deep Oxidation

Co3O4, MgCo2O4 and MgO materials have been synthesized using a simple co-precipitation approach and systematically characterized. The total conversion of toluene to CO2 and H2O over spinel MgCo2O4 with wormlike morphology has been investigated. Compared with single metal oxides (Co3O4 and MgO), MgCo2O4 with the highest activity has exhibited almost 100% oxidation of toluene at 255 °C. The obtained results are analogous to typical precious metal supported catalysts. The activation energy of toluene over MgCo2O4 (38.5 kJ/mol) is found to be much lower than that of Co3O4 (68.9 kJ/mol) and MgO ((87.8 kJ/mol)). Compared with the single Co and Mg metal oxide, the as-prepared spinel MgCo2O4 exhibits a larger surface area, highest absorbed oxygen and more oxygen vacancies, thus highest mobility of oxygen species due to its good redox capability. Furthermore, the samples specific surface area, low-temperature reducibility and surface adsorbed oxygenated species ratio decreased as follows: MgCo2O4 > Co3O4 > MgO; which is completely in line with the catalytic performance trends and constitute the reasons for MgCo2O4 high excellent activity towards toluene total oxidation. The overall finding supported by ab initio molecular dynamics simulations of toluene oxidation on the Co3O4 and MgCo2O4 suggest that the catalytic process follows a Mars–van Krevelen mechanism.

Mingled Metal Oxides Catalyst for Direct Carbonylation of Glycerol into Glycerol Carbonate

AbstractThe escalation of CO2 into the atmosphere has encouraged the development of sustainable pathways to produce materials and chemicals from CO2. In the present manuscript, an attempt has been made for direct carbonylation of glycerol into Glycerol carbonate (GC) by using CO2 over mingled metal oxide (MMO) catalyst. Several single, bi and trimetal oxides catalysts were explored for direct carbonylation of glycerol. Among the tested catalysts, Cu incorporated MMO showed the profound effect to obtain maximum glycerol conversion and GC selectively. However, a series of MMO catalysts with variable Cu loading were synthesized by simple co‐precipitation method and tested for direct carbonylation of glycerol. Of all tested Cu loaded MMO catalyst, 5 % Cu loaded MMO catalyst (CuO/CeO2/ZnO) showed highest GC selectivity (99 %). Furthermore, the process intensification study was conducted to investigate the influence of various reaction parameters on glycerol conversion and GC yield such as catalyst loading, temperature, CO2 pressure, time, and solvent concentration. The intensified process resulted into 57.4 % glycerol conversion with 57.2 % GC yield and 99.65 % selectivity. Moreover, the in‐depth physicochemical characterisations of the synthesised MMO catalyst were conducted by using various surface analytical techniques. The synthesised MMO has showed a synergistic and protagonistic effect for direct carbonylation of glycerol. The recyclability study was performed to examine the robustness and efficency of the MMO catalyst that showed the consistency in the GC yield, conversion and selectivity without any significant loss after six consecutive runs. Also, the plausible reaction mechanism over MMO catalyst was proposed. The reported methodology has explored a simple, robust and efficient process for direct carbonylation of glycerol by using MMO catalyst with higher yield and selectivity of GC.

A newly isolated indigenous metal-reducing bacterium induced Fe and Mn oxides synergy for enhanced in situ As(III/V) immobilization in groundwater

Iron-manganese binary oxides (Fe-Mn oxides) have the potential to immobilize arsenite/arsenate [As(III/V)] in situ in natural environments. However, the As(III/V) immobilization performances of Fe-Mn oxides in the presence of indigenous metal-reducing bacteria in reducing groundwater systems have received limited attention. Here, As(III/V) immobilization by Fe-Mn oxides and the interactions of Fe and Mn oxide components in groundwater in the presence of a newly isolated indigenous metal-reducing bacterium (Bacillus sp. FMR) were investigated. Microcosm experiments were performed with artificial groundwater and mineral phases (Fe, Mn and Fe-Mn oxides) with As(III) or As(V) in the presence or absence of strain FMR under anoxic conditions. The Fe oxides in anaerobic cultures without bacteria exhibited better immobilization performances for As(III) [69% As(T) removal efficiency] and As(V) (70%) than Mn oxides (19% and 17%, respectively). Comparably, the involvement of bacteria induced the re-release of arsenic adsorbed on the single Fe and Mn oxides under anoxic conditions, whereas this shift in arsenic adsorption–desorption was not observed in Fe-Mn oxide systems because the Mn oxide components inhibited the reductive dissolution of the Fe oxide components. The As(T) removal efficiencies of Fe-Mn oxides in the presence of bacteria increased by 17% for As(III) and 16% for As(V) compared with anaerobic incubation without bacteria. The interaction of Fe and Mn oxides in Fe-Mn oxides resulted in a slightly increased mobilization of As(III/V) in the absence of bacteria, whereas there was a synergistic effect in the presence of bacteria. The favorability of indigenous bacteria for As(III/V) immobilization and the synergy between Fe and Mn oxides provide novel insights for in-situ As(III/V) immobilization in high arsenic-containing groundwater.

Covalent Organic Framework Based Functional Materials: Important Catalysts for Efficient CO2 Utilization.

As hot topics in the chemical conversion of CO2 , the photo-/electrocatalytic reduction of CO2 and use of CO2 as a supporter for energy storage have shown great potential for the utilization of CO2 . However, many obstacles still exist on the road to realizing highly efficient chemical CO2 conversion, such as inefficient uptake/activation of CO2 and mass transport in catalysts. Covalent organic frameworks (COFs), as a kind of porous material, have been widely explored as catalysts for the chemical conversion of CO2 owing to their unique features. In particular, COF-based functional materials containing diverse active sites (such as single metal sites, metal nanoparticles, and metal oxides) offer great potential for realizing CO2 conversion and energy storage. This Minireview discusses recent breakthroughs in the basic knowledge, mechanisms, and pathways of chemical CO2 conversion strategies that use COF-based functional catalysts. In addition, the challenges and prospects of COF-based functional catalysts for the efficient utilization of CO2 are also introduced.

Covalent Organic Framework Based Functional Materials: Important Catalysts for Efficient CO2Utilization

AbstractAs hot topics in the chemical conversion of CO2, the photo‐/electrocatalytic reduction of CO2and use of CO2as a supporter for energy storage have shown great potential for the utilization of CO2. However, many obstacles still exist on the road to realizing highly efficient chemical CO2conversion, such as inefficient uptake/activation of CO2and mass transport in catalysts. Covalent organic frameworks (COFs), as a kind of porous material, have been widely explored as catalysts for the chemical conversion of CO2owing to their unique features. In particular, COF‐based functional materials containing diverse active sites (such as single metal sites, metal nanoparticles, and metal oxides) offer great potential for realizing CO2conversion and energy storage. This Minireview discusses recent breakthroughs in the basic knowledge, mechanisms, and pathways of chemical CO2conversion strategies that use COF‐based functional catalysts. In addition, the challenges and prospects of COF‐based functional catalysts for the efficient utilization of CO2are also introduced.

Facile Synthesis of Zn-Co-S Nanostrip Cluster Arrays on Ni Foam for High-Performance Hybrid Supercapacitors.

Mixed metal sulfides exhibit outstanding electrochemical performance compared to single metal sulfides and mixed metal oxides because of their richer redox reactions and high electronic conductivity. In the present study, Zn-Co-S nanostrip cluster arrays were formed from ZnCo2O4 grown on Ni foam by an anion exchange reaction using a two-step hydrothermal process. Morphological characterization confirmed that the Zn-Co-S nanostrip cluster arrays had grown homogeneously on the skeleton of the 3D Ni foam. The length of the nanostrip was approximately 8 µm, and the width ranged from 600 to 800 nm. The Ni foam-supported Zn-Co-S nanostrip cluster arrays were assessed directly for electrochemical supercapacitor applications. Compared to ZnCo2O4, the Zn-Co-S electrode exhibited a three-fold higher specific capacity of 830 C g−1 at a specific current of 2.0 A g−1. The higher polarizability, lower electro-negativity, and larger size of the S2− ion played an important role in substituting oxygen with sulfur, which enhanced the performance. The Zn-Co-S//AC hybrid device delivered a maximum specific energy of 19.0 Wh kg−1 at a specific power of 514 W kg−1. The remarkable performance of Zn-Co-S nanostrip cluster arrays highlights their potential as a positive electrode for hybrid supercapacitor applications.

Graphite felt modified withWO3,SnO2,and binaryWO3/SnO2‐mixtures as novel positive electrodes for cerium‐based redox flow batteries

Cerium-based redox flow batteries (RFBs) such as Zn-Ce and V-Ce have received attention as attractive energy storage systems due to their high open-circuit cell voltages. To date, the most successful Ce-based RFBs have relied on expensive Pt-based positive electrodes. In this study, the use of more economical polyacrylonitrile (PAN)-based graphite felt (GF) containing tungsten oxide (WO3) and/or tin oxide (SnO2) nanocatalysts is examined for its electrochemical activity for the Ce(III)/Ce(IV) redox reaction in a series of half-cell experiments. Cyclic voltammetry is carried out at room temperature in a 0.05 M Ce(III) methanesulfonate +1.0 M methanesulfonic acid (MSA) electrolyte using a custom-made three-electrode cell. Among all modified GFs, those coated with a binary WO3-SnO2 mixture have exhibited superior electrocatalytic activity toward the Ce(III)/Ce(IV) reaction compared to the ones decorated with single oxides WO3 or SnO2. Presumably, this can be ascribed to the involvement of both metal oxides (WO3 and SnO2) in promoting electrolyte accessibility and improving the hydrophilicity of GF electrodes. SEM images indicate that the combination of WO3 and SnO2 promotes a more homogeneous dispersion over the graphite fiber surface and prevents clustering of the oxide particles that is more evident in the case of the single metal oxide catalysts.

Oxide scale behavior of Al–7.5 mass%Mg alloy containing trace Ca during short-term oxidation

In this study, using transmission electron microscopy and phase diagrams from thermodynamic calculations, we investigated the oxide film formation of Al–7.5 mass%Mg alloy containing Ca traces during short-term oxidation in terms of the thermodynamic stability and multi-element oxides by inter-diffusion based on the results of analysis for the oxide film. For the oxidation test at 515 ˚C, for 1 h, its results showed that there is no significant difference between the Ca-added and Ca-free Al–7.5 mass%Mg alloys was observed, while further exposure caused the Ca-free alloy to gain significant weight. Based on the standard Gibbs free energy for oxide production calculated in this study, CaO was the most preferential product among the single metal oxides examined. As per calculations for MgAl2O4-spinel formation reactions, the spinel formation from MgO was thermodynamically the most favorable. According to the phase diagrams calculated in this study, various multi-element oxides including Ca could possibly form in the oxide layer of Ca-added alloy. The analysis results of transmission electron microscopy confirmed that MgO is the primary oxide in the Al–Mg binary alloys. In oxidation tests conducted for less than 1 h, the spinel was rarely found. The outmost areas of oxide layers correspond to MgO and CaO in Ca-free and Ca-added alloys, respectively. However, in the Ca-added alloy, the inner layer contains certain amounts of Ca, Al, and Mg.

Complementary operando insights into the activation of multicomponent selective propylene oxidation catalysts

Two Bi–Mo–Co–Fe–O catalysts were synthesized by flame spray pyrolysis and tested for their catalytic performance in selective oxidation of propylene to acrolein. Pronounced structural changes during temperature–programmed oxidation and reaction were observed by operando X–ray absorption spectroscopy, X–ray diffraction, Raman spectroscopy, and thermogravimetric analysis. During oxidative treatment, mainly binary oxide phases (α–Bi2Mo3O12, β–CoMoO4, Fe2(MoO4)3) were observed, but single (MoO3) or ternary (Bi3(FeO4)(MoO4)2) oxides also formed depending on the relative elemental catalyst composition. During propylene oxidation, the reduction of Fe3+ to Fe2+ led to a strong rise in activity and induced further phase transformations. MoO3 was found to be unselective towards acrolein but was essential in binding other single oxides. The formation of β–Co0.7Fe0.3MoO4 and Bi3(FeO4)(MoO4)2 as well as their synergistic interplay with α–Bi2Mo3O12 are key factors for high performance. The combination of complementary operando methods was crucial to reveal new structure–activity/selectivity correlations, therefore bridging the knowledge gap between simplified model systems and complex applied catalysts.

Enhanced catalytic performance of spinel-type Cu-Mn oxides for benzene oxidation under microwave irradiation

Microwave-assisted heterogeneous catalytic oxidation of benzene was investigated over Cu-Mn spinel oxides. The spinel oxides were synthesized by a coprecipitation method from metal nitrate hydrolysis in a solution using tetramethylammonium hydroxide (TMAH) as a precipitation reagent. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption fine structure, scanning electron microscopy, transmission electron microscope and H2-temperature-programmed reduction studies. Microwave absorption by the Cu-Mn spinel oxide is mainly driven by dielectric losses (dielectric heating). Cu-Mn spinel oxide with a Cu/Mn ratio of 1 exhibited superior activity to single oxides under microwave heating, demonstrating lower apparent activation energy than that obtained under conventional heating. Microwave irradiation lowered the reaction temperature required for benzene oxidation compared with conventional heating. Transient tests were used to investigate the reactivity of oxygen species in the catalytic reaction, and the high reactivity of Cu-Mn spinel oxides was related to the high reactivity of lattice oxygen on the catalyst surface. The reactivity of the oxygen species was enhanced under microwave heating, leading to an enhanced benzene oxidation reaction. The combination of adsorption and catalytic oxidation processes using Cu-Mn spinel oxides and zeolites efficiently decomposed benzene at low concentrations.

A facile green synthesis of porous hexagonal cobalt pyrovanadate electrode for supercapacitors by deep eutectic solvent

Cobalt vanadate is a kind of promising electrode material for pseudo-supercapacitors because of their higher electrical conductivity, better electrochemical activity, and prominent specific capacitance than single metal oxides. In this paper, cobalt pyrovanadate (Co2V2O7) was primarily fabricated by a facile environment-friendly ionothermal method using a green deep eutectic solvent (DES) and followed the heat treatment in the air. The eutectic mixture discussed here was consisted of a hydrogen bond donor (urea) and acceptor (ChCl) in a 2:1 molar ratio. The as-prepared Co2V2O7 was porous hexagonal nanoplatelets, and its electrochemical performances were characterized by cycle voltammetry, galvanostatic charge/discharge and cycling stability tests in a three-electrode system with 2 M KOH electrolyte solution. The specific capacitance of the synthesized Co2V2O7 revealed 304 F g−1 at the current density of 1 A g−1. Surprisingly, it remained an excellent cycle performance with 103% in 100 charge/discharge cycles. Therefore, we have successfully presented a deep eutectic solvent derived routine to prepare porous hexagonal Co2V2O7 nanoplatelets electrode material.

A novel non-enzymatic sensor for prostate cancer biomarker sensing based on electrocatalytic oxidation of sarcosine at nanostructured NiMn2O4 impregnated carbon paste electrode

This work addresses the electrocatalytic activity of a binary metal oxide catalyst of NiMn2O4 for electroxidation of sarcosine, the well-known prostate cancer biomarker. The nanocatalyst described was prepared via hydrothermal synthesis route, followed by calcination at 800 °C. Field emission scanning electron microscopy and X-ray diffraction were applied to obtain information about the material morphology and structure. A carbon paste electrode modified with nano-NiMn2O4 showed unique catalytic activity in sarcosine electroxidation which led to a significant rise in oxidation current (about four times) in comparison with the blank electrode. However, the carbon paste electrodes containing single oxides of NiO and Mn2O3 exhibited no considerable enhancement in sarcosine signal. The cyclic voltammetry results indicated that the Mn3+/Mn4+ couple was responsible for sarcosine oxidation, and NiO may enhance the content of Mn4+species in NiMn2O4 material. The carbon paste-based NiMn2O4 electrode was applied in the sensitive determination of sarcosine in the concentration range of 0.01–5.0 μM with the relative standard deviation of 3.49% (n = 5). The detection limit and quantification limit of the probe were determined to be 3.8 and 12 nM, respectively. The remarkable sensitivity and high selectivity of the method approved the sensor applicability in measurement of sarcosine content in urine samples.

Design of ZIF-67 MOF-derived Co3O4/NiCo2O4 nanosheets for supercapacitor electrode materials

Binary transition metal oxides exhibit improved properties including good redox potentials and electrical conductivities compared with single metal oxides as electrode materials in energy storage. Herein, ZIF-67 is prepared by a one-step method using Co2+ as the central metal ion, 2-methylimidazole as the organic ligand, and methanol as an organic solvent at room temperature. Hollow NiCo2O4 and sheet-like Co3O4/NiCo2O4 derived from bimetallic imidazolate framework precursors were synthesized by adding cobalt and nickel ions in appropriate proportions. A hollow and porous structure is achieved for the reaction between a nickel salt and ZIF-67, and this unique nanostructure provides a high active surface area, which is beneficial to the electrochemical properties. Several samples are prepared and used as electrode materials for electrochemical tests in 6 M KOH. As a result, the Co3O4/NiCo2O4 electrode with a sheet nanostructure showed a high specific capacitance of 846 F g−1 at a current density of 0.5 A g−1. This Co3O4/NiCo2O4 electrode material is promising for future studies on high-performance supercapacitors to solve emerging energy-related problems. [Formula: see text]

The effect of alloying elements on oxide scale spallation of multicomponent Co-based superalloys

The characterization of high temperature cyclic oxidation behavior of as-cast and as-aged Co-(Ni)-Al-W alloys, and the influence of alloying elements on oxide spallation resistance have been investigated in this study. The cyclic oxidation and oxide scale morphology of the alloys are analyzed from 700° to 900°C. It has been observed that the ternary Co-Al-W alloys are prone of oxide scale spallation and increasing the Al, W and Ni contents improves the cyclic oxidation resistance of the alloys. The structural effect of Ni on oxidation performance is related to its introduction to single and complex oxides present in a scale.

Photocatalytic activity of α-Fe2O3@CeO2 and CeO2@α-Fe2O3 core-shell nanoparticles for degradation of Rose Bengal dye

Core-shell structures of mixed oxides have great interest due to their physical and chemical properties. The present study aims to determine the structural, magnetic, and optical characteristics of the core-shell structure of α-Fe2O3@CeO2 and CeO2@α-Fe2O3 nanoparticles and their application in the purification of dye contaminates water. These core-shell nanoparticles were synthesized by the cost-effective hydrothermal method with weight ratios as α-Fe2O3:CeO2 (1:1, 2:1) and CeO2:α-Fe2O3 (1:1, 1:2). XRD pattern revealed two distinct phases corresponding to Fe2O3 and CeO2 in synthesized core-shell structures. Defects/oxygen vacancies in lattice were determined using XPS spectra. Magnetic studies indicate that the magnetic character of pure Fe2O3 was found higher with maximum magnetization of 0.84 emu/g than other synthesized materials due to the contribution of non-magnetic CeO2. The maximum photodegradation efficiency of core-shell nanoparticles [α-Fe2O3@CeO2 (2:1)] for Rose Bengal dye was found to be 93% in 75 min under UV irradiation source as compare to the single metal oxides i.e., α-Fe2O3 and CeO2. The Ce4+/Ce3+ and Fe2+/Fe3+ redox couple and heterojunction interfaces of core-shell material have promoted electron transfer and photo-excited electron-hole recombination. These properties of core-shell materials are significant for the photodegradation of Rose Bengal dye.

Analysis of fluorescence characteristics of Sm3+-doped B2O3-rich glasses for Orange-light-emitting diodes

Optical absorption and visible luminescence aspects including visible emission decay times have been examined for six Sm3+ (1 mol%)-doped B2O3-rich glasses comprising single and mixed alkali oxides which were synthesized via melting-and-quenching approach. Upon intense λexci. = 409 nm, fluorescence spectra displayed four bands peaked at 562 nm, 598 nm, 645 nm, and 706 nm owing to 4G5/2 upper level to 6H5/2, 6H7/2, 6H9/2, and 6H11/2 lower levels transitions respectively. Among identified emissions, orange fluorescence (598 nm) is found to be strong in all samples. Moreover Sm3+: Li ions having sample exhibits the dominant visible emissions band intensity in all samples, so for this sample, Judd–Ofelt (JO) analysis was carried out to calculate JO parameters Ωt (t = 2, 4, 6), and from them, radiative transition probabilities, branching ratios (calculated and experimental), and radiative lifetimes of Sm3+: 4G5/2 level to distinct lower energy states were derived utilizing absorption and emission spectra. CIE (Commission Internationale de l′éclairage) coordinates, correlated color temperature (CCT), color purity, color rendering index, and luminous efficiency of radiation were determined from visible luminescence spectra of all studied glasses, and obtained CIE coordinates and CCT values lie in the reddish-orange light region of CIE diagram, indicating their potential for orange LEDs (light-emitting diodes) application. Here derived CCT values are lower than the typical warm light sources CCT limit (<3200 K). 4G5/2 state luminescence decay patterns revealed double exponential behavior for assessing the measured lifetimes. Effective bandwidth, stimulated emission cross-section, and gain bandwidth were computed for observed luminescence transitions of Sm3+: Li ions possessing sample.

Pr3+-doped B2O3–Bi2O3–ZnO–NaF glasses comprising alkali/mixed alkali oxides for potential warm white light generation, blue laser, and E-+S-+C-optical bands amplification applications

For six 1 mol% Pr 3+ -doped B 2 O 3 –Bi 2 O 3 –ZnO–NaF glasses consisting of single and mixed alkali oxides, optical absorption and visible and near-infrared (NIR) luminescence traits including visible fluorescence decay times were investigated. Judd–Ofelt (J‒O) analysis from absorption spectra was performed to calculate J‒O parameters Ω λ ( λ = 2, 4, 6) by including and omitting 3 H 4 → 3 P 2 transition. Utilizing Ω 2 , Ω 4 , and Ω 6 values and refractive indices, radiative transition probabilities ( A R ), branching ratios ( β R ), and radiative lifetimes for all Pr 3+ ion's luminescent levels were estimated. For observed intense blue fluorescence band upon 443 nm optical pumping, various parameters considered in designing visible laser systems were evaluated. Pr 3+ : Na + K ions comprising glass possesses large spectroscopic quality factor, high A R and β R , large stimulated emission cross-section ( σ em ), high quantum efficiency, large gain bandwidth, and significant optical gain for 3 P 0 → 3 H 4 transition for a potential blue lasing action among all samples. Further, Commission Internationale de l'éclairage (CIE) coordinates, correlated color temperature (CCT), color rendering index, and luminous efficiency of radiation were derived from visible luminescence spectra and deduced CIE and CCT values represent the neutral or warm white light region. Upon 3 H 4 → 3 P 2 excitation, NIR luminescence spectra show 3 P 1 + 1 I 6 → 1 G 4 , 1 D 2 → 3 F 4 , and 1 D 2 → 1 G 4 transitions in which broadband ( 1 D 2 → 1 G 4 ) at 1.3–1.65 μm range with effective bandwidth ~157 nm was obtained for Pr 3+ : Na + K ions constituting glass with high A R (1938 s −1 ), moderate β R (26%), and large σ em (2.64 × 10 −20 cm 2 ) at 1.472 μm, and its gain profile covers the E-+S-+C-optical communication bands' range for effective broadband amplification operation.

Resynthesis of NMC111 Cathodic Material from Real Waste Lithium Ion Batteries

In this work, the role of the experimental conditions during the synthesis of LiNi1/3Mn1/3Co1/3O2 cathodic material (NMC) precursor was evaluated. Precursor synthesis was carried out starting from the electrodic powder obtained from the mechanical treatment of spent lithium ion batteries. Metals were extracted by acid-reducing leaching of the electrodic powder with an extraction yield higher than 90%. Cobalt was the most concentrated metals followed by manganese and nickel. Iron, copper and aluminium, coming from battery cases and current collectors, were present as impurities in the leachate. Selective precipitation of the impurities was performed prior to precipitate the mixed hydroxide. Ni1/3Mn1/3Co1/3(OH)2 precipitations were carried out using two concentrations of NH4OH and under nitrogen or air atmosphere. The effect of these parameters was evaluated on the NMCs structure by XRD analysis and on the electrochemical performance by the galvanostatic cycling of the NMCs when assembled in half lithium cells. XRD analysis of the NMCs have showed the obtainment of the typical layered structure of LiNi1/3Mn1/3Co1/3O2 for any synthesized NMC and no other phases related to single oxides were found. The evaluation of the electrochemical performance has showed a significant role of the precipitation atmosphere and an improvement of the specific capacity was attained using the lowest concentration of NH4OH. Remarkably, specific capacity values of recovered NMCs were comparable to NMCs synthesized under the same experimental conditions but using synthetic reagents.

Ab initio based interionic interactions in calcium aluminotitanate oxide melts: structure and diffusion

Calcium aluminotitanate (CaO–Al2O3–TiO2) ternary oxides are of fundamental interest in Materials as well as Earth and environmental science, and a key system for several industrial applications. As their properties at the atomic scale are scarcely known, interionic interactions for the melts are built from a bottom up strategy consisting in fitting first only Al2O3, CaO and TiO2 single oxide compounds separately with a unified description of the oxygen charge and O–O interaction term. For this purpose, a mean-square difference minimization of the partial pair-correlation functions with respect to the ab initio reference was performed. The potentials for the ternary oxide are finally built straightforwardly by adding purely Coulomb terms for dissimilar cation–cation interactions without further fit. This general and unified approach is transferable and successfully describes the structural and diffusion properties of the three single oxides as well as the ternary melts simultaneously. A possible underlying structural mechanism at the origin of the diffusion evolution with TiO2 content is proposed based on the formation of Ti induced triply bonded oxygen.

3D-Printing of Proton Conducting Ceramics

3D-printing technology is being extensively utilized in energy sector, as it allows for manufacturing complex structures (compacted stacks, desired microarchitectures and porosity) and customizable shapes for specific devices. Moreover, fast prototyping time and reduction of production cost make this technology promising for industrial applications. Up to now, plenty of 3D-printed energy conversion and storage devices and hence precursor materials have been proposed. Reported examples concern solar cells, biofuel cells, rechargeable ion batteries, carbon-based supercapacitors and others [1-2]. On the other hand, 3D-printing of proton-conducting materials is rarely reported. The pioneering research was presented by Mu et al., who have developed novel laser 3D-printing method which allows to obtain protonic ceramics with the desired crystal structures, microstructures, and geometries [3]. The method consists of the preparation of printable paste from component raw materials (carbonate and single metal oxides) mixed with sintering aid, the deposition of a thin green film of the targeted protonic ceramics, and the reactive sintering by rapid CO2 laser scanning. Such method was successfully applied for the synthesis of dense electrolytes (e.g. BCZYYb, BZY20), porous electrodes (e.g. BCZYYb+NiO, BaCo0.4Fe0.4Zr0.1Y0.1O3-δ), dense interconnect (La0.7Sr0.3CrO3-δ/LSC), and dense mixed protonic and electronic-conduction composite (BaCe0.85Fe0.15O3-δ– BaCe0.15Fe0.85O3-δ/BCF) [4]. The second available example is devoted to the 3D-printed proton exchange membrane and has been recently reported by K. Iwase and co-workers [5]. Scientists developed UV-cured ink (mixture of proton-conducting ionic liquids, inorganic silica nanoparticles, and UV-sensitive photocurable resins) which can be successfully applied to the printing of proton exchange membranes.In the present study, we developed 3D-printing of protonic ceramics- Ba0.5La0.5Co1-xFexO3-δ (0 ≤x≤ 1), which are promising materials for positrodes in protonic ceramic fuel cells [6]. The Project is devoted both to the construction of 3D-printer and ink preparation. Two printing technology- fused deposition modeling and extrusion-based 3D-printing were selected and embedded into one 3D-printer. In addition, the system was equipped with IR laser for post-processing. Ink (solid filament or gel) was prepared from ceramic powder and polymer (i.e. polylactic acid or polyvinyl alcohol), which act as a matrix and is removed at the end. Various compositions (e.g.ceramic to polymer ratio, polymer concentration, solvent) and synthesis conditions (e.g. time, temperature) were tested. A lot of attention was paid to the proper ceramic dispersion, which ensures printouts homogeneity. Therefore, various approaches such as ball-milling of ceramic and ultrasonication of gel were optimized and implemented. The last important step was devoted to the laser post-processing, during which polymer is removed and ceramic is sintered. Various laser powers, scan speeds and number of scans were tested. Printed layers before and after post-processing were characterized by X-Ray diffraction, Fourier Transform Infra-Red spectroscopy and Scanning Electron Microscopy. In the future it is planned to adopt developed technology and use it for the printing of multi-layered positrodes with graded functionality.