Oxygen Ion Transfer Research Articles

Electrochemical upcycling of indium-gallium-zinc oxide scraps

At present, the processes of recovering indium-gallium-zinc oxide (IGZO) scraps through hydrometallurgy, pyrometallurgy, or molten salt electro-deoxidation are cumbersome, impurities cannot well be effectively removed, and the environmental benefits are inferior. We herein firstly propose a facile electrochemical method for upcycling of IGZO scraps in ammonium salt aqueous solution at ambient temperature. The feasibility of electro-deoxidation of IGZO in aqueous solution has been verified, using IGZO scraps without further crushing as the cathode and anode. The electro-deoxidation behavior of various oxides exhibits differentiation, among which indium oxide is the most easily deoxidized. This difference hinders the formation of a dense alloy layer on the surface of the IGZO substrate, facilitating the transfer of oxygen ions and enabling continuous electro-deoxidation. Impurities such as aluminum and silicon can be significantly removed, with removal rates of 95.8 % and 75.7 %, respectively, which is also attributed to the difference in electrochemical reduction ability between impurity oxides and IGZO, as well as the solid-state existence of cathode products. The process of upcycling IGZO scraps contributes to recovery with straightforward operation and more adaptable implementation environment, which endows it with optimistic application potential.

Evaluating the impact of ZnO doping on electrical and thermal properties of calcium-aluminosilicate oxynitride glass-ceramics

This study aimed to investigate the impact of ZnO content on the structure, thermal, and electrical properties of oxynitride glass-ceramic(s) within the Ca–Al–Si–O–N (CASON) system. The base glass had the composition of Ca7Al14Si17O52N7, with ZnO additions ranging from 3 to 15 % by weight. A pristine Ca7Al14Si17O52N7 glass was successfully prepared by melt-quenching technique followed by converted into glass-ceramic by incorporating various amounts of ZnO using the field-assisted sintering technique. XRD and FESEM analysis confirmed that increasing the amount of Zn increases the crystallinity in the glass matrix. The observed crystalline phases were formed mostly from ZnO and showed higher conductivity than the remaining dielectric matrix. IR spectra confirmed the presence of bands correlated with the presence of Zn and suggested the progressive depolymerization of the silicate-aluminate network as a consequence of increasing Zn content. Density values varied between 2.75 and 2.94 gcm−3 and increased with increasing the Zn content in the glass-ceramic. The thermal expansion and thermal conductivity values increased and decreased, respectively, with the increase of Zn content in the matrix. The electrical properties of the samples were investigated using impedance spectroscopy over a wide range of frequencies (10 mHz to 1 MHz) and temperatures (153 K–623 K). The results showed that in the glass without ZnO and glass-ceramic(s) with a small addition of ZnO, the conductivity is mainly dominated by the transfer of oxygen ions and, to a small extent, by the presence of electronic conductivity. As the ZnO content increases, continuous conduction paths are formed between the ZnO crystallites, and the electrical conductivity increases rapidly and becomes dominated by electron transfer.

Oxygen-ion and proton conductivity in the Ba3InGa2O7.5 complex oxide with incomplete oxygen sublattice

The Ba3InGa2O7.5 complex oxide, possessing the perovskite-related structure with structural oxygen vacancies, was first synthesized by the solid state method. The phase was found to be characterized by monoclinic symmetry (sp. gr. P2/c) with the following unit cell parameters: a = 7.942(1) Å, b = 5.868(5) Å, c = 18.201(6) Å, b = 91.52(9). Comprehensive investigations of electrical properties were carried out; ceramic material based on the complex oxide was shown to be a predominantly ionic conductor in the temperature range 450–900 oC. The conductivity is due to oxygen-ion transfer in dry conditions and oxygen-ion and proton transfer in wet atmosphere. The proton conductivity value is 4.5·10–5 S/cm, and the proton transport number is ~50% at 700 oC in wet air; at lower temperatures, proton transport becomes dominant. Prolonged treatment of the sample in water vapors below 450 oC leads to hydrolysis decomposition.

The electrical properties of codoping LaInO<sub>3</sub> perovskite

This paper is devoted to the study of LaInO3 based co-doped materials. Solid solutions in which lanthanum is substituted for strontium have sufficiently high conductivity values, but a low level of oxygen deficiency is realized. Mg2+ and Ca2+ ions were chosen as co-dopants for the B sublattice. Both series of the investigated La0.9Sr0.1In1-xCaxO2.95–0.5x and La0.9Sr0.1In1-yMgyO2.95-0.5y solid solutions crystallize in orthorhombic symmetry with sp. gr. Pnma. The ionic conductivity in a dry atmosphere is determined by the oxygen ions transport. Oxygen-ion transfer in solid solutions is ~30–40% at high temperatures (T 700°C) and increases to 80% as the temperature decreases to 400–300°C. The substitution Ca2+ with In3+ increases the electrical conductivity of the oxygen ions; the highest values are achieved for the compositions La0.9Sr0.1In0.95Ca0.05O2.925 and La0.9Sr0.1In0.9Ca0.1O2.9. The introduction of Mg2+ co-dopant at the In3+ positions leads to a decrease in ionic conductivity compared to La0.9Sr0.1InO2.95. The effects of changing oxygen mobility with changing geometric factors (cell volume, critical radius) are discussed.

A-Site Nonstoichiometric BaxCo0.4Fe0.4Zr0.1Y0.1O3-δ Cathode for Protonic Ceramics Fuel Cells.

Highly active triple (proton, oxygen-ion, and electron) conducting materials BaxCo0.4Fe0.4Zr0.1Y0.1O3-δ (BxCFZY, x = 0.9-1.1) were prepared and characterized as potential cathodes for protonic ceramic fuel cells (PCFCs) in this work. The crystal structure, oxygen vacancy concentration, electrical conductivity, oxygen ion transfer properties, and electrochemical performance of BxCFZY oxides were systematically evaluated. The electrical conductivity of BxCFZY decreases but oxygen vacancies increase with increasing Ba content, indicating that the charge compensation was mainly achieved by the production of oxygen vacancy rather than the increase in the valence of transition metal cations. The power density of 1170 mW cm-2 and the polarization resistance of 0.05 Ω cm2 were achieved at 700 °C for the anode-supported single cells with B1.1CFZY cathode, suggesting that the excess A site on the BxCFZY had a positive effect on the catalytic activity for the oxygen reduction reaction. Furthermore, the distribution of relaxation time (DRT) analysis method was adopted to determine the electrochemical processes of the cells with BxCFZY cathodes. The calculated results confirmed that the cell with B1.1CFZY cathode exhibited the optimum performance due to the best oxygen ion transfer properties in BxCFZY cathodes.

Sulfur Dioxide Oxidation by Zinc and Zinc Oxide Nitrate/Nitrite Complexes in the Gas Phase: An Interplay between Redox-Active Ligands and Metal.

Different oxidative pathways of sulfur dioxide promoted by ZnO(NO3 )2 - , Zn(NO3 )2 - and Zn(NO2 )(NO3 )- are revealed by a joint investigation by mass spectrometry and theoretical calculations. The reactions are triggered by [Zn2+ -O- ⋅]+ or by the low-valence Zn+ through oxygen ion transfer or electron transfer to SO2 , respectively. The NOx - ligands intervene in the oxidation only when sulfur dioxide is converted to SO3 - or SO2 - , leading to the formation of zinc sulfate and zinc sulfite coordinated to nitrate or nitrite anions. Kinetic analyses show that the reactions are fast and efficient, and theory discloses the elementary steps, namely oxygen ion transfer, oxygen atom transfer and electron transfer, occurring through similar energy landscapes for the three reactive anions.

Mathematical Model of Metal–Oxide Memristor Resistive Switching based on Full Physical Model of Heat and Mass Transfer of Oxygen Vacancies and Ions

Herein, a 1D mathematical model of memristor resistive switching that includes a full physical model of steady‐state heat and mass transfer is developed. The model considers ions and vacancies generation, recombination, and drift in an electric field in the memristor structure with dominant charge transport mechanism of electron tunnel hopping through vacancies. The distributions of vacancy concentration depending on the applied voltage and the given temperature of the memristor are found by numerical simulation. A good agreement is obtained between the part of the simulated current–voltage characteristics and the experimental one. There is no noticeable temperature gradient in a forming‐free nonfilament memristor. Therefore, the calculation of the vacancy concentration and the current–voltage characteristics in a forming‐free memristor with constant temperature over the film is appropriate. It is shown that the ion‐vacancy recombination can be neglected at temperatures over 600 K. In that case, the equation for ions, as well as the recombination term in the equation for vacancies can be neglected. The developed model at the same time consider all the processes occurring in the oxide layer and allow to reduce the computational complexity without significant loss of accuracy. The proposed model can be used to model large memristor arrays.

The promoting effect of Sr-doping on the oxygen reduction activity of perovskite cathode

A stable cathode with high catalytic activity toward oxygen reduction reaction (ORR) plays a key role in the commercialization of solid oxide fuel cells (SOFCs). The cathode material Ba0.8Sr0.2Co0.7Fe0.2Nb0.1O3-δ is synthesized by solid-state reaction method. The introduction of Sr result in a higher porosity and a lower thermal expansion coefficient. It optimizes the concentration ratio of small polarons and oxygen vacancies. The overall reaction of Ba0.8Sr0.2Co0.7Fe0.2Nb0.1O3-δ cathode is determined by three main ORR processes. The change in rate-limiting step are related to partial pressure of oxygen. The ionization process of oxygen atoms is the main rate-limiting step when PO2 is higher than 0.01 atm. The addition of Sr2+ accelerates the ionization process of oxygen atoms and leads to the acceleration of the whole ORR process. The temperature mainly affects the oxygen transport on the cathode surface and in the cathode bulk. The transfer of oxygen ions to the electrolyte and the ionization of oxygen atoms are accelerated at high temperatures.

Solid Oxide Fuel Cells with 3D Inkjet Printing Modified LSM-YSZ Interface

Solid oxide fuel cells (SOFCs) have drawn attention as an alternative power generation technology due to demonstrated high efficiency and low emissions. The lanthanum strontium manganite (LSM)-yttria-stabilized zirconia (YSZ) cathode is utilized widely for SOFCs due to its high performance and stability. The electrochemical oxygen reduction reaction that occurs in the cathode can be enhanced by the porous LSM-YSZ cathode with good electronic and ionic conductivity. With sufficient electrochemically active reaction sites, the oxygen ion transfer processes in the mixed ionic conductor (YSZ) and at the interface of cathode and electrolyte (LSM-YSZ) become critical for the activity of the cathode. Thus, the pillar shape YSZ microstructure with ~ 150 μm×150 μm×10 μm (L×W×H) size can be fabricated by 3D inkjet printing on the interface of electrolyte and cathode to increase the TPB area and enhance the connection between the dense YSZ electrolyte and mixed YSZ ionic conductor. Scanning Electron Microscopy (SEM) is utilized to assess the morphology and microstructure of the YSZ interface. To investigate the influence of the modified interface on the performance of the SOFC, electrochemical performance testing and characterization are conducted for the SOFCs with/without the modified YSZ layer. The microstructures with different pillar central spacing are also fabricated by 3D inkjet printer to optimize the geometry of the LSM-YSZ interface.

Mathematical modeling of memristor resistive switching based on mass transfer full model of oxygen vacancies and ions

A relatively simple mathematical model of dynamic switching of a memristor has been created based on a fairly complete physical model of the processes of stationary mass transfer of oxygen vacancies and ions, considering their generation, recombination and diffusion in electric field in the “metal-oxide-metal” structure with the dominant transport mechanism of electron tunneling through oxygen vacancies. The results of numerical simulation of mass transfer of oxygen vacancies along thickness of the oxide layer of the memristor are presented. The distributions of vacancy concentration during their diffusion in an electric field are found, taking into account the processes of generation and recombination with ions, depending on the applied voltage to the electrodes and on the temperature of the memristor. A good coincidence of the volt-ampere characteristics part found as a result of numerical simulation and a series of experiments is obtained. It is shown that under conditions of more than 600 K memristor temperature, it is possible to neglect the process of ion-vacancy recombination and significantly simplify the procedure for mathematical modeling of memristor resistive switching by eliminating the oxygen mass transfer equation, as well as the recombination term in the stationary equation of oxygen vacancies mass transfer. The developed mathematical model of memristor dynamic switching, including a system of stationary ordinary differential equations, is designed to simulate the operation of large memristor arrays in neuromorphic computing devices and may be preferable in relation to known circuit models that include a certain set of fitting parameters to match the simulation results with the memristor experimental characteristics.

Flash Light Sintered Lanthanum Strontium Cobalt Ferrite(LSCF) Electrode for High Performance IT-SOFCs

The high temperature(900oC~) thermal sintering process is necessary to fabricate the Solid oxide fuel cells(SOFCs). However, the chemical reaction has occurred between solid oxide material components, electrode and electrolyte. In the case of lanthanum strontium cobalt ferrite (La0.6Sr0.4Co0.2Fe0.8O3-δ, LSCF) electrode, the SrZrO3(SZO) secondary phase is produced at the electrolyte interface even when using the gadolinium doped ceria(GDC) buffer layer for blocking the strontium and zirconium diffusion. The SZO layer hinders the oxygen ion transfer and deteriorates fuel cell performance. By using a novel flash light sintering(FLS) method, we have successfully solved the problem of secondary phase formation in the conventional high temperature thermal sintering process. The microstructure and thickness of the LSCF electrode are analyzed using a field emission scanning electron microscope(FE-SEM). The strontium diffusion and secondary phase are confirmed by X-ray diffraction (XRD), energy dispersive spectrometer method of SEM, TEM (SEM-, TEM-EDS). The NiO-YSZ anode supported LSCF cathode cells are adopted for electro chemical analysis which is measured at 750oC. The maximum power density of the thermal sintered LSCF cathode at 1050oC is 699.6mW/cm2, while that of the flash light sintered LSCF cathode is 711.6mW/cm2. This result proves that the electrode was successfully sintered without a secondary phase using flash light sintering.

Suitability of Iron (Fe)-Doped Tungsten Oxide (WO3) Nanomaterials for Photocatalytic and Antibacterial Applications

Pure and “Fe ([Formula: see text][Formula: see text]wt.%)-doped” WO[Formula: see text] nanoparticles were prepared by facile microwave irradiation method and that was investigated for strong photo catalytic and antibacterial activity applications for the first time. The primary aim of this work is to reveal the great importance of oxygen vacancies ([Formula: see text] due to dopant (Fe[Formula: see text] for photo catalytic and antibacterial activity applications. This work also discusses the contribution of oxygen vacancies and their dependence on surface area and phase formation which are of great research interest for water purification and biological sciences. Herein, pure and “Fe ([Formula: see text][Formula: see text]wt.%)-doped” WO[Formula: see text] nanoparticles were successfully synthesized by facile microwave irradiation (MWI) method (2.45 GHz/240W/10min) in ambient atmosphere. The phase formation and the crystalline nature of the prepared products were evaluated using powder X-ray diffraction (XRD). It confirmed the phase formation of orthorhombic and monoclinic phase formations for the pure (WO[Formula: see text]H2O) and annealed samples (W[Formula: see text]O[Formula: see text] and WO[Formula: see text], respectively. Optical behavior of the samples from UV-Vis diffuse reflectance analysis revealed that W[Formula: see text]O[Formula: see text] has remarkable bandgap values (1.96[Formula: see text]eV) that clearly emphasizes the transfer of oxygen ions which helps in the movement of oxygen vacancies inside the crystalline domain. The morphological nature of the prepared products was observed by FE-SEM analysis and the average dimension was found to be 0.2–3.2[Formula: see text][Formula: see text]m and 2–4[Formula: see text][Formula: see text]m for the pure and annealed products, respectively. The specific surface area from BET analysis explored that W[Formula: see text]O[Formula: see text] having 55.16[Formula: see text]m2g[Formula: see text] was found to be higher than that of commercially available WO3. The photocatalytic behavior of the prepared compounds morphologies was investigated via Rhodamine B (RhB) degradation under visible light irradiation. These results showed “Fe-doped” annealed WO3 nanoparticles have degradation efficiency of 86.9% along with high stable nature. On the other hand, to identify the suitability of the prepared products for antibacterial activity, the microbial strains of Gram-positive Bacillus sp. and Gram-negative strains of Pseudomonassp. and Salmonellasp. were used for the antimicrobial assay[Formula: see text] The results indicated that W[Formula: see text]O[Formula: see text] showed enhanced antibacterial nature when compared to that of Stoichiometry tungsten oxide (WO[Formula: see text] nanomaterials. From these observations, this work emphasizes the importance of oxygen vacancies for antibacterial activity applications.

Conducting Property and Performance Evaluation of LNF as Cathode Current Contact Layer in Solid Oxide Fuel Cell

Electrical performance, durability and degradations are challenging issues for Solid Oxide Fuel Cell (SOFC) commercialization. Ce0.9Gd0.1O2-δ (GDC) and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) are current gold material system in SOFC, which mainly works as barrier layer and cathode, respectively. However, the porous GDC barrier layer and vulnerable cathode/electrolyte interface often leads to high ohmic resistances and fast degradations. Herein, we develop and report a novel approach for barrier layer and cathode modifications, using cost-competitive and scalable hydrothermal reaction.Results show that, the as-sintered porous GDC barrier layer is filled up with in-situly grown Ceria based nano particles during hydrothermal reaction, yielding improved density and sintering-active surface, simultaneously. After co-sintered with cathode, the cell obtains optimized cathode/barrier layer interface, exhibiting decreased ohmic and cathode polarization resistances with higher electrical performance and less degradation.On the other aspect, the Ceria based nano particles are also observed in-situly precipitated on LSCF powder surface during hydrothermal reaction, forming dual-phase LSCF@GDC cathode, which also yields decreased ohmic and polarization resistance than pristine LSCF.Above results suggest that hydrothermal modifications are effective for barrier layer and cathode/electrolyte interface optimizations. Thus, the improved oxygen ion transfer and interface contact are beneficial for SOFC electrical performance and long-term operation. Furthermore, this hydrothermal modification is applicable in many other surface and interface optimizations.

Lower down both ohmic and cathode polarization resistances of solid oxide fuel cell via hydrothermal modified gadolinia doped ceria barrier layer

Hydrothermal reaction in Cerium and Gadolinium solution as an optimization method is developed and first reported for the densification of gadolinia doped ceria, the barrier layer between Zirconia electrolyte and (La,Sr)(Co,Fe)O3-δ cathode. This method is based on the hydrothermal reaction for nano particles in-situly grown on porous surface, to improve barrier layer density, alongside the sintering of cathode at 1075 °C. As a result, the ohmic resistance is prominently decreased by ∼16.4 % at 750 °C for electrolyte supported symmetrical cell. Whereas, the cathode polarization resistance is decreased by as much as a factor of ∼3 from 0.3702 Ω·cm2 to 0.1325 Ω·cm2 at 750 °C and pO2=0.21 atm. Furthermore, the anode supported cell exhibits higher open circuit voltage, smaller area specific resistance, elevated performance output and less degradation. And this modified barrier layer shows reduced Sr migration in 300 h operation at 750 °C. The hydrothermal reaction is demonstrated to prepare denser and sintering-active barrier layer with faster oxygen ion transfer and better interface connection, with large-scale application prospects and cost-competitiveness.

Demonstration of a ceria membrane solar reactor promoted by dual perovskite coatings for continuous and isothermal redox splitting of CO2 and H2O

The direct one-step CO2 and H2O splitting using an oxygen-transport membrane (OTM) reactor was investigated as a potentially ideal way to generate renewable fuels from concentrated solar energy. The solar-driven thermolysis of CO2 (or H2O) was promoted by in-situ oxygen removal across nonstoichiometric ceria-based membranes. A new solar membrane reactor integrating a tubular densified membrane made of either pure ceria or perovskite-coated ceria was designed and operated under high-flux concentrated solar radiation. A continuous flow of inert gas on the permeate side was used to create the required oxygen partial pressure gradient (driving force) and ensure continuous oxygen permeation via oxygen ion diffusion across the densified ceria membrane. The continuous OTM solar operation at high temperature was demonstrated through testing under various operating conditions. The CO and O2 production rates were sharply enhanced by increasing the operating temperature (up to 1550 °C). The increase of CO2 concentration or oxidant gas flow rate also enhanced the process performance. Unprecedented fuel production rates (>0.07 μmol s−1 cm−2 at 1550 °C) were achieved with a pure CO2 stream on the feed side and flowing Ar on the sweep side of the reactive ceria membrane. An original composite membrane integrating two different perovskite coatings on each side of the ceria membrane, with a sandwich-like structure, was designed and tested under concentrated sunlight. Thin layers of La0.5Sr0.5Mn0.9Mg0.1O3 on the inner side and Ca0.5Sr0.5MnO3 on the outer side were added to enhance oxygen ion transfer. With such a membrane configuration, a remarkable production of CO (>0.13 μmol s−1 cm−2) and oxygen (with CO:O2 ratio of 2) was obtained simultaneously, respectively on the inner and outer sides of the OTM. These results outperform the production rates achieved with the uncoated ceria membranes, and demonstrate the benefits of using composite membranes composed of a densified core material coated with (or sandwiched in between) redox active perovskite materials.

Two‐Dimensional Boron and Nitrogen Dual‐Doped Graphitic Carbon as an Efficient Metal‐Free Cathodic Electrocatalyst for Lithium‐Air Batteries

AbstractThe cathode catalyst for lithium‐air (Li‐air) batteries has a critical effect on battery performance. In this study, a two‐dimensional (2D) boron and nitrogen dual‐doped graphite carbon (BNC) catalyst prepared through a carbonization process was studied as a highly active electrocatalyst in Li‐air batteries. BNC offered high contents of boron and nitrogen as well as a graphene‐like structure. When employed as the catalyst for Li‐air batteries, it demonstrated good electrochemical performance, in terms of superior discharge capacity, low voltage gap, and long‐term stability. The as‐prepared special structure of BNC promoted the formation and diffusion of superoxide O2− and, meanwhile, reduced the oxygen release barrier by improving the charge transfer of oxygen ions.

ELECTROCATALYSIS OF THE OXYGEN REACTION ON THE MULTICOMPONENT OXIDES OF TRANSITION METALS

The review presents the current state of research on oxides of transition metals as electrocatalysts for the both reactions of oxygen reduction and evolution, which are of key importance ones for electrochemical devices of alternative energy: metal-air rechargeable batteries and fuel cells with an oxygen electrode. The review includes the consideration of the thermodynamic, electronic and adsorption conditions for activation of the molecular oxygen by oxide surface, as well as the advantages of the oxide surfaces as catalysts in the alkaline electrolytes. The influence of the chemical composition and structural features of oxides of transition elements on the adsorption and chemisorption of water and oxygen, the formation of ionic forms at adsorption and the main factors, which influence on transfer of electrons, protons and oxygen, are considered. Synthesis of double and other multicomponent oxides and the usage of cationic doping expands the possibilities of forming the necessary properties of the electrocatalysts: porosity, thickness of hydrated layers, electronic and ionic conductivity, proton and electron-donor (acceptor) properties in a optimal combination. The oxide should have a metal with variable valence, and even better if there are two ones. Such oxides can be various structures based on Co2O3, MnO2, Ni2O3, Mn3O4, Fe2O3, and others. A qualitative leap in improving the performance of catalysts for electrode reactions with oxygen was made possible by the synthesis of nanoparticles, as well as nanocomposites with metallic and carbon materials. The some characteristics of the electroca­talytic activity of promising oxide electrocata­lysts, mainly, multicomponent ones, as well as the results of studies of oxide composites with carbon nanomaterials, are presented. Several of the most well-known oxide structures (spinel, perovskite, pyrochlor) are currently being studied as the most promising matrices for the efficient transfer of charge, oxygen, and metal ions. All of them are multicomponent. The most active non-platinum bifunctional catalysts for oxygen reactions concluded to be cobaltites with spinel structure. Nanocomposites based on cobalt and cobalt-manganese spinel are the most promising materials for use in alkaline rechargeable batteries, both in terms of cost and in terms of electrocatalytic activity as well as in terms of corrosion resistance.

Study of the oxygen reduction reaction on pure and Zr-doped YMnO3+δ SOFC electrode

The effect of Zr-doping on the novel SOFC cathode YMnO3 and its O2-Reduction Reaction (ORR) was studied using electrochemical impedance spectroscopy (EIS) as a function of temperature (500 < T < 800 °C) and the oxygen partial pressure (10−4 < pO2 < 1 atm). EIS technique allows identifying three processes controlling the ORR for each electrode, differentiated by their characteristic frequency, activation energies and pO2 dependence. High frequency contribution, only observed at 600°C for both electrodes, was attributed to oxygen ion transfer trough the electrode/electrolyte interface. In both electrodes, the Intermediate frequency contribution was described by a Gerischer impedance, related to a co-limiting process between oxygen ion diffusion and a surface process. However, whereas the EIS characteristics for YMnO3 can be explained by a surface process controlled by the electron transfer from oxide to O-adsorbed, it seems related for Y0.9Zr0.1MnO3 to the probability of finding a second free-surface site near to a diatomic intermediated for the O2 dissociation. These differences are in agreement with the improvement of the electrical properties when YMnO3 is doped with Zr. The low frequency contribution became important as pO2 decreased and temperature increased, and its characteristics would indicate a secondary surface process, co-limited with O2 gas diffusion for Y0.9Zr0.1MnO3 porous electrode.

All‐Solid‐State Electro‐Chemo‐Mechanical Actuator Operating at Room Temperature

AbstractDimensional change in a solid due to electrochemically driven compositional change is termed electro‐chemo‐mechanical (ECM) coupling. This effect causes mechanical instability in Li‐ion batteries and solid oxide fuel cells. Nevertheless, it can generate considerable force and deformation, making it attractive for mechanical actuation. Here a Si‐compatible ECM actuator in the form of a 2 mm diameter membrane is demonstrated. Actuation results from oxygen ion transfer between two 0.1 µm thick Ti oxide\Ce0.8Gd0.2O1.9 nanocomposite layers separated by a 1.5 µm thick Ce0.8Gd0.2O1.9 solid electrolyte. The chemical reaction responsible for stress generation is electrochemical oxidation/reduction in the composites. Under ambient conditions, application of 5 V DC produces actuator response within seconds, generating vertical displacement of several µm with calculated stress ≈3.5 MPa. The membrane actuator preserves its final mechanical state for more than 1 h following voltage removal. These characteristics uniquely suit ECM actuators for room temperature applications in Si‐integrated microelectromechanical systems.

Topotactic phase transformations by concerted dual-ion migration of B-site cation and oxygen in multivalent cobaltite La–Sr–Co–Ox films

Manipulating topotactic phase transformations via orderly ion transfer in complex oxides ABO x is ubiquitous in advanced applications such as ionotronics, ion-batteries and catalysts. Most of such ion-mediated transformations are accomplished by the transfer of oxygen or A-site ions. However, implementing the transformation via the transfer of B-site ions, despite the great challenge to overcome a large cohesive energy, has unique advantage since they host most functional properties of materials. Here, we present a tri-state phase transformation from perovskite (P) to brownmillerite (BM) and to single-layered perovskite (SL) structure via the concerted migration of oxygen and B-site Co-ions in La 0.7 Sr 0.3 CoO 3 thin films. Ac-STEM, XPS, XAS, PNR, magnetic and electric measurements demonstrated that presented B-site Co-cation transfer is along the CoO 4 tetrahedral sub-layer of the BM film, which leads to the reconfiguration of 3 d -electrons and spin state in remanent Co ions and causes tremendous changes in magnetic and electric properties: from canted-antiferromagnetic insulator in BM phase to ferromagnetic insulator in SL phase. First-principles calculations revealed that the La 3+ -doping at A-site largely reduces the cohesive energy of Co-ions in CoO 4 and destabilize the CoO 4 tetrahedron of BM phase, which explains the formation of Co-ions transfer channel in the CoO 4 tetrahedral sub-layer. The present study highlights the effectiveness of regulating topotactic transformation via B-site ions transfer and provides a new pathway for manipulating the topotactic transformation with diverse functionalities. Tri-state topotactic transformation induced by B-site Co ion transfer was firstly realized in La 0.7 Sr 0.3 CoO 3 film. A unique transfer channel for Co-ions is demonstrated to be facilitated by the instability of CoO 4 due to A-site La-doping. The reconfiguration of 3d-electrons due to Co transfer leads to tremendous changes in magnetic and electric properties. Such new topotactic transformation driven by B-site ion transfer offers opportunity to exploit new types of electrocatalyst with rich functionalities. • Tri-state topotactic transformation induced by B-site Co ion transfer was firstly realized in La 0.7 Sr 0.3 CoO 3 film. • A unique transfer channel for Co-ions is demonstrated to be facilitated by the instability of CoO 4 due to A-site La-doping. • The concerted transfer of Co and O ions drive tremendous changes in magnetic and electric properties. • Such B-site ion transfer provides a new pathway for exploiting electrocatalyst with diverse functionalities.