Oxygen Vacancy Concentration Research Articles

The Study of the Etching Resistance of YOF Coating Deposited by Atmospheric Plasma Spraying in HBr/O2 Plasma

Yttrium oxyfluoride (YOF) coatings with different oxygen content were prepared using atmospheric plasma spraying (APS) technology. The etching resistance of the coatings in HBr/O2 plasma was investigated. Shifts in diffraction peaks of the X-ray diffraction, along with XPS analysis conducted before and after etching, demonstrated that Br ions could replace O and F ions and fill the oxygen vacancies after exposure to HBr/O2 plasma, which is supported by the first-principles calculations. Br ions formed a protective layer on the surface of the YOF coating, slowing down further etching by Br ions. By adjusting the oxygen mass fraction in YOF powder, the oxygen vacancy concentration and Br ion filling were regulated to enhance etching resistance. YOF coatings with 6% oxygen content exhibited improved etching resistance compared to YOF coatings with 3% and 9% oxygen content. This improvement was primarily due to the increased Br ion concentration. These findings provide a new approach for developing coatings with enhanced etching resistance.

Thermal stability and coalescence dynamics of exsolved metal nanoparticles at charged perovskite surfaces

Exsolution reactions enable the synthesis of oxide-supported metal nanoparticles, which are desirable as catalysts in green energy conversion technologies. It is crucial to precisely tailor the nanoparticle characteristics to optimize the catalysts’ functionality, and to maintain the catalytic performance under operation conditions. We use chemical (co)-doping to modify the defect chemistry of exsolution-active perovskite oxides and examine its influence on the mass transfer kinetics of Ni dopants towards the oxide surface and on the subsequent coalescence behavior of the exsolved nanoparticles during a continuous thermal reduction treatment. Nanoparticles that exsolve at the surface of the acceptor-type fast-oxygen-ion-conductor SrTi0.95Ni0.05O3−δ (STNi) show a high surface mobility leading to a very low thermal stability compared to nanoparticles that exsolve at the surface of donor-type SrTi0.9Nb0.05Ni0.05O3−δ (STNNi). Our analysis indicates that the low thermal stability of exsolved nanoparticles at the acceptor-doped perovskite surface is linked to a high oxygen vacancy concentration at the nanoparticle-oxide interface. For catalysts that require fast oxygen exchange kinetics, exsolution synthesis routes in dry hydrogen conditions may hence lead to accelerated degradation, while humid reaction conditions may mitigate this failure mechanism.

Preparation and Properties of Fe-Based Double Perovskite Oxide as Cathode Material for Intermediate-Temperature Solid Oxide Fuel Cell

Double perovskite oxides with mixed ionic and electronic conductors (MIECs) have been widely investigated as cathode materials for solid oxide fuel cells (SOFCs). Classical Fe-based double perovskites, due to their inherent low electronic and oxygen ionic conductivity, usually exhibit poor electrocatalytic activity. The existence of various valence states of B-site ions modifies the material’s catalytic activity, indicating the possibility of the partial substitution of Fe by higher-valence ions. LaBaFe2−xMoxO5+δ (x = 0, 0.03, 0.05, 0.07, 0.1, LBFMx) is used as intermediate-temperature solid oxide fuel cell (IT-SOFC) cathode materials. At a doping concentration above 0.1, the Mo substitution enhanced the cell volume, and the lattice expansion caused the formation of the impurity phase, BaMoO4. Compared with the parent material, Mo doping can regulate the oxygen vacancy concentration and accelerate the oxygen reduction reaction process to improve the electrochemical performance, as well as having a suitable coefficient of thermal expansion and excellent electrode stability. LaBaFe1.9Mo0.1O5+δ is a promising cathode material for IT-SOFC, which shows an excellent electrochemical performance, with this being demonstrated by having the lowest polarization resistance value of 0.017 Ω·cm2 at 800 °C, and the peak power density (PPD) of anode-supported single-cell LBFM0.1|CGO|NiO+CGO reaching 599 mW·cm−2.

Electronic Structure Modulating of W18O49 Nanospheres by Niobium Doping for Efficient Hydrogen Evolution Reaction.

Hydrogen, known for its high energy density and environmental benefits, serves as a prime substitute for fossil fuels. Nonetheless, the hydrogen evolution reaction (HER), essential in electrolysis, encounters challenges with slow kinetics and significant overpotential, which elevate costs and reduce efficiency. Thus, developing efficient electrocatalysts to reduce HER overpotential is vital to enhance hydrogen production efficiency and minimize energy consumption. Adjusting the electronic structure of transition metal oxides via elemental doping is a potent strategy to improve the effectiveness of electrocatalysts for hydrogen evolution. In this work, we synthesized a set of niobium-doped tungsten oxides (Nbx-W18O49) under anoxic conditions using a straightforward "one-pot" solvothermal approach. After doping Nb, the oxygen vacancy content inside W18O49 was increased, which induced a synergistic effect with the active sites of tungsten. In acidic environments, the hydrogen evolution activity of the Nb0.6-W18O49 electrocatalyst is second only by 20 wt % Pt/C. It attains a current density of -10 mA cm-2 at an overpotential of 102 mV. By comparison with W18O49, Nb0.4-W18O49 and Nb0.5-W18O49, Nb0.6-W18O49 demonstrates a reduced charge transfer resistance, which significantly enhances its conductivity and the speed of electron movement across interfaces. Coupled with this feature are notably faster HER kinetics. Additionally, it exhibits excellent stability, meaning it maintains its performance and structural integrity over prolonged periods and under various operational conditions. This article provides a new perspective for discovering inexpensive and efficient hydrogen evolution electrocatalyst materials.

Enhanced H2S removal efficiency using CuO/Al2O3 catalyst impregnated with Ca(NO3)2: Influence of calcination temperature and mechanistic insights

A series of Ca(NO3)2-CuxO/Al2O3 catalysts with different calcination temperatures were designed to remove H2S effectively. Experimental and characterization results indicate that the calcination temperature can influence the catalyst's specific surface area, basic sites, and oxygen vacancies (VOs) concentration, thereby promoting its desulfurization performance. The Ca(NO3)2-CuxO/Al2O3 catalyst, calcined at 230 °C, exhibits an optimal surface structure. It demonstrates optimal H2S desulfurization performance at a temperature of 60 °C and relative humidity of 60 %, achieving a removal capacity of 486.67 mg/g. The VOs in CuxO (CuO and Cu2O) induce a unique catalytic of H2O, which generates hydroxy radicals (·OH) to oxidize the H2S anion to S. The introduction of Ca2+ provides basic sites to buffer pH, and NO3- with H+ removes H2S through cyclic oxidation, significantly enhancing the desulfurization performance of the Cu-based catalyst. The CaO-CuxO/Al2O3 catalyst, calcined at 700 °C, suffers from a deteriorated catalyst structure, leading to the rapid formation of desulfurization by-products due to the presence of CaO covering the catalyst surface. This diminishes the effectiveness of Cu, significantly impairing the catalyst's desulfurization performance (150.47 mg/g). Consequently, desulfurization mechanisms of Ca(NO3)2-CuxO/Al2O3 and CaO-CuxO/Al2O3 are proposed, offering effective strategies for the design and optimization of subsequent high-efficiency catalysts.

An electrochemiluminescence sensor for ultrasensitive determination of tyrosine based on ceria nanomaterial as a novel luminophor

BackgroudRecently, optical nanomaterials have attracted much attention in the field of electrochemiluminescence (ECL). Nanostructured ceria possessed unique optical properties, and it's always used for constructing ECL sensor as catalyst for improving sensing performance, while the ECL property of ceria is rarely studied. In fact, it could be the potential candidate for applying in ECL sensors based on size and shape dependency optical property caused by the quantum scale effects. Therefore, new simple and efficient ceria nanomaterial used as luminophor for constructing the ECL sensor have aroused more research interest and motivation. (91 words). ResultsIn the work, three kinds of nanostructured ceria, ceria nano-cube (CeO2-NC), ceria nano-rods (CeO2-NR) and ceria nano-particle (CeO2-NP), have been prepared by hydrothermal method, and CeO2-NC with the less oxygen vacancy has the highest ECL signal. Moreover, how the shape affects the ECL property was investigated in detail, especially the oxygen vacancy on the surface of the ceria. The less of oxygen vacancy content of CeO2 nanomaterials is more favorable the ECL reaction. Furthermore, a novel ECL sensor was constructed based on reduced graphene oxide (rGO), Au nano-particle (AuNPs) and CeO2-NC for Tyrosine (Tyr) determination owing to the electron transform between the luminous of ceria and Tyr resulting in the cathodic ECL intensity quenched correspondingly, and it has possessed excellent sensing performance with a linear range of 0.005–20 nmol/L and the limit of detection (LOD) value of 1.7 fmol/L (141 words) Significance and noveltyThe proposed method demonstrated excellent selectivity and ultra-sensitivity toward Tyr, which had been used for the determination of Tyr in human serum successfully, possessing outstanding analytical performance. Therefore, nanostructured ceria is a new category of efficient and promising luminophore, which would open new avenues for the potential application in the field of ECL sensing for clinical diagnosis. (57 words).

Anomalous resistive switching effect in La0.8Ca0.2MnO3/Nb:SrTiO3 structure

A barrier-type resistive switching (RS) unit, composed of a metal and Nb:SrTiO3 (NSTO), holds significant potential for data storage applications due to its high storage density, low operating voltage, and excellent stability. While extensive research has been conducted on conductive oxides (COs), there has been relatively less focus on the RS properties of heterogeneous structures combing CO electrodes and NSTO. Epitaxial growth of CO on NSTO is expected to yield devices with enhanced stability and repeatability. This study explores the RS characteristics of La0.8Ca0.2MnO3 (LCMO)/NSTO heterostructures through epitaxy of both conventional and anoxic LCMO films on (00 l)-oriented NSTO single crystal substrates. The results reveal that the conventional LCMO/NSTO structure exhibits a conventional counterclockwise bipolar RS (BRS) effect, while the anoxic LCMO/NSTO heterostructure demonstrates a unique clockwise (CW) BRS effect (exhibiting different RS characteristics under different applied voltages). The study concludes that the CW-BRS effect mechanism is attributed to a high concentration of oxygen vacancies (Vo) in LCMO. Under different external electric fields, Vo in LCMO and NSTO migrate to the LCMO/NSTO interface, respectively, leading to multiple changes in the interface barrier. These findings offer valuable experimental insights for utilizing CO in the field of RS applications.

A highly-efficient peroxymonosulfate activator using a sewage sludge derived biochar supported cobalt oxide: Mechanism and characteristics

The application of biochar derived from sewage sludge (BS) in Fenton-like reactions for contaminant removal has attracted considerable attention. Herein, a BS-supported Co3O4 (BS-Co3O4) catalyst was synthesized using a simple two-step hydrothermal-calcination process to achieve highly efficient activation of peroxymonosulfate (PMS). The introduction of biochar effectively inhibited the aggregation of Co3O4 and reduced cobalt leaching. Compared to Co3O4, the mesoporous BS-Co3O4 exhibited an 8-fold increase in specific surface area (SSA) to 111.92 m2∙g−1, and a 46 %-66.4 % reduction in crystal plane size. The interaction between biochar and cobalt oxide resulted in several notable enhancements in the BS-Co3O4 composite. Specifically, there was an increase in sp2 carbon content, a 42.69 % rise in capacitance, and a 79.99 % reduction in charge transfer resistance. These improvements contributed to enhanced PMS activation performance. The BS-Co3O4 also contained a higher content of Co(II), sp2 carbon, and oxygen vacancies (OV). Co(II) played a crucial role in the redox reaction, accelerating the formation of SO4•− and 1O2 during the PMS activation process. Additionally, OV acted as electron capture centers, further promoting the generation of 1O2. Evidence from reactive species investigations and electron paramagnetic resonance (EPR) tests indicated that SO4•− and 1O2 were the main reactive radicals for eliminating tetracycline (TC). Based on the identification of TC intermediates, two potential degradation pathways were proposed, and a reduction in intermediate toxicity was observed. Experiments involving interference and repetition demonstrated that the BS-Co3O4 catalyst was stable and reusable. This work provides a solution with low metal leaching, high recycling performance, and safety for antibiotic wastewater treatment.

Synergistic effects of liquid phase sintering and B-site substitution to enhance proton conductivity of BaZr0.1Ce0.7Y0.1Yb0.1O3-δ for protonic ceramic fuel cell

This paper is dedicated to improving the sintering and conductivity of BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) by adding ZnO-CuO dual-sintering aids. The synergistic effects of liquid-sintering of Zn and B-site substitution of Cu on the sinterability and proton conductivity of BZCYYb are systematically investigated. X-ray diffraction (XRD) analysis of BZCYYb after addition of ZnO-CuO (BZCYYb-Zn-Cu) confirms the complete perovskite phase formation without any secondary phase. The substitution of Ce4+ (0.87 Å) with Zn2+ (0.74 Å) or Cu2+ (0.73 Å) induces a shift in XRD diffraction peak to higher angle due to a decrease in lattice constant. Energy dispersive X-ray spectroscopy analysis indicate a distinct distribution of Zn primarily at the grain boundaries, while Cu is predominantly located within the grains of BZCYYb-Zn-Cu. The addition of ZnO-CuO into BZCYYb results in a denser microstructure with larger average grain size. Furthermore, the substitution of Ce4+ by Cu2+ increases the concentration of oxygen vacancies and reduces activation energy. For BZCYYb-Zn-Cu, the proton conductivity reaches 4.52×10-2 S/cm at 750 °C, approximately 3 times higher than that of BZCYYb. This enhancement can be attributed to the synergistic effects of larger average grain size resulting from liquid phase sintering of Zn, low active energy, and high concentration of oxygen vacancies arising from Cu B-site substitution. BZCYYb-Zn-Cu is used as the electrolyte for anode support SOFC, and the single cell exhibits remarkable electrochemical performance and excellent stability in H2 fuel. This research establishes a crucial theoretical foundation for the preparation and performance evaluation for large-size protonic ceramic cell.

Preparation and Electrochemical Performance of Alkaline Earth Metal-Doped Nd2Ce2O7 Proton Conductor Hydrogen Separation Membranes

Nd2Ce2O7 is a rare earth oxide with a fluorite structure and exhibits proton conductivity. Alkaline earth metals (Mg, Ca, Sr, Ba) doped Nd2Ce2O7 powders were synthesized using the citrate sol-gel method. The doped samples retain the fluorite structure, and enhanced oxygen vacancy concentration. Notably, Nd1.85Mg0.15Ce2O7-δ exhibited the highest oxygen vacancy concentration, reaching an electrical conductivity of 2.91×10-2 S•cm-1 in a humid atmosphere of 20%H2 and 80%N2 at 900°C. Hydrogen separation membranes were fabricated using alkaline earth metal-doped Nd2Ce2O7 as the proton-conducting phase and Pt as the electron-conducting phase. The results indicated that Pt-Nd1.85Mg0.15Ce2O7-δ had the optimal hydrogen permeation flux, reaching 8.35×10-9 mol•cm-2•s-1 at 900°C. It demonstrated short-term stability in environments containing CO2 and H2O, and an increase in temperature and hydrogen partial pressure on the feed side enhanced hydrogen permeation, highlighting its potential as a hydrogen separation membrane material.

Tailoring the catalytic activity of PrBaFe2O5+δ cathode material with non-transition metal In-doping for solid oxide fuel cells

Double perovskite PrBaFe2O5+δ (PBF) is a promising cathode material for solid oxide fuel cell (SOFCs) due to the favorable catalytic activity and superior electrochemical stability. Herein, to further tailor the oxygen-ion transport kinetics and electrochemical performance, unlike the typical approach through using higher valence, non-transition metal In3+ ion doping is initially investigated to partially replace Fe3+/Fe4+ site, forming the compositions of PrBaFe2−xInxO5+δ (PBFInx, x = 0, 0.05, 0.1, and 0.15). Xray diffraction (XRD) analysis indicates that PBFInx exhibit satisfactory chemical and thermal compatibility with the gadolinia-doped ceria (GDC) electrolyte. Expectedly, the polarization resistance (Rp) of PBFIn0.1 cathode is decreased by approximately 40 % and an anode-supported single cell with PBFIn0.1 cathode yields a 36 % higher peak power density (PPD) at 800 °C compared to that of PBF. Moreover, the single cell using PBFIn0.1 as the cathode can be operated stably at 0.4 A cm−2 for more than 50 h without obvious performance degradation. In addition, the X-ray photoelectron spectroscopy (XPS) results confirm that the low-valence state In3+ introduced into PBF have a positive impact on the oxygen vacancy concentration and boost the oxygen reduction reaction (ORR) activity, thus significantly enhancing the electrochemical performance of the PBF cathode. The results show that the non-transition metal In3+ ion doping is an effective method to improve the performance of the PBF cathode for SOFCs.

Performance study of solid electrolyte Ce0.80Gd0.04Sm0.04Er0.04Y0.04RE0.04O2-δ (RE= Yb, Dy, Eu, Nd, Pr, La)

The production of highly conductive electrolytes has been a crucial factor in the practical development of Solid Oxide Fuel Cells (SOFCs). This study highlights the impact of different dopants on the crystal structure, microstructure, and ionic conductivity of a ceria-based matrix within the Ce0.80Gd0.04Sm0.04Er0.04Y0.04RE0.04O2-δ system. The Ce0.80Gd0.04Sm0.04Er0.04Y0.04RE0.04O2-δ (RE = Yb, Dy, Eu, Nd, Pr, La) powders were prepared using the solid-state reaction method. The phase structure, microstructure, and ionic conductivity of the GSEYRE series electrolytes were analyzed using XRD, SEM, EDS, TEM, XPS, AC impedance spectroscopy, and thermal expansion analysis. Phase structure analysis confirmed that all multi-doped electrolytes possessed a cubic fluorite structure with the Fm3m space group. After sintering at 1400°C for 10 hours, all samples exhibited densities exceeding 94%. XPS analysis revealed a high concentration of oxygen vacancies in the GSEYRE. Electrical performance analysis showed that the Ce0.80Gd0.04Sm0.04Er0.04Y0.04Dy0.04O2-δ (GSEYD) electrolyte demonstrated the highest ionic conductivity (σt = 3.36×10-2 S/cm) and the lowest activation energy (Ea = 0.78 eV) at 800°C. The thermal expansion coefficient of the developed electrolytes matched well with commonly used electrode materials. These characteristics make GSEYD a promising candidate for use as an electrolyte material in SOFCs.

Upcycling CO2 and bio-derived furan into degradable plastic monomer via coupling of photocatalysis and thermocatalysis

Coupling of CO2 with biomass-derived molecules into degradable plastic monomer provides a promising strategy to address the increasing problems of carbon recycle and carbon neutrality. Herein, we develop a sustainable route to produce 6-hydroxycaproate (6-HMC) by coupling photocatalytic carboxylation of biomass-derived furfuryl alcohol with CO2 to 2-furanacetic acid (FA), and the thermocatalytic hydrogenolysis of methyl 2-tetrahydrofuranyl acetate (MTFA) derived from FA, wherein Pd/CeO2 exhibit the highest productivity of 6-HMC (505 mmol6-HMC mmol-1metal h−1), much higher than its counterparts of precious- and non-precious-metal catalysts. Moreover, Pd/CeO2 also presents good stability for 6 recycles without remarkable decrease in 6-HMC yield. Systematic experiments and computational studies suggest that higher concentration of oxygen vacancies and strong metal-support interactions account for enhanced catalytic performance of Pd/CeO2. The work employs CO2 and lignocellulosic-derived platform molecule as feedstocks to produce valuable degradable plastic monomer, providing a promising route to access pure-CO2 originated high-carbon oxygen-containing compounds.

Effect of oxygen plasma treatment on the properties of ALD hafnium oxide films

In this work, we studied the effect of processing hafnium oxide samples prepared by atomic layer deposition in a gas discharge plasma of a mixture of argon and oxygen in a ratio of 1:10. It has been shown that such treatment preserves the amorphous structure of the film and reduces the content of oxygen vacancies in the film. This is important for the use of the film in the gate dielectric of a transistor. Processing in plasma leads to a change in its properties, namely: an increase in density and refractive index, as well as a decrease in the intensity of emission bands that are associated with an oxygen vacancy. The plasma temperature and ion energy were determined from the argon emission spectra. The activation energy for the diffusion of oxygen ions in hafnium oxide films has been calculated to be 0.43 eV.

Platelet Ceria Catalysts from Solution Combustion and Effect of Iron Doping for Synthesis of Dimethyl Carbonate from CO2.

Solution combustion (SC) remains among the most promising synthetic strategies for the production of crystalline nanopowders from an aqueous medium, due to its easiness, time and cost-effectiveness, scalability and eco-friendliness. In this work, this method was selected to obtain anisometric ceria-based nanoparticles applied as catalysts for the direct synthesis of dimethyl carbonate. The catalytic performances were studied for the ceria and Fe-doped ceria from SC (CeO2-SC, Ce0.9Fe0.1O2-SC) in comparison with the ceria nanorods (CeO2-HT, Ce0.9Fe0.1O2-HT) obtained by hydrothermal (HT) method, one of the most studied systems in the literature. Indeed, the ceria nanoparticles obtained by SC were found to be highly crystalline, platelet-shaped, arranged in a mosaic-like assembly and with smaller crystallite size (≈6 nm vs. ≈17 nm) and higher surface area (80 m2 g-1 vs. 26 m2 g-1) for the undoped sample with respect to the Fe-doped counterpart. Although all samples exhibit an anisometric morphology that should favor the exposition of specific crystalline planes, HT-samples showed better performances due to higher oxygen vacancies concentration and lower amount of strong basic and acid sites.

Hierarchical Ordered Mesoporous Sr2Bi4Ti5O18 Microflowers with Rich Oxygen Vacancies In Situ Assembled by Nanosheets for Piezo-Photocatalysis.

The Aurivillius phase layered perovskite ferroelectric material Sr2Bi4Ti5O18 (SBTO) exhibits spontaneous polarization and piezoelectric properties, which confer significant potential for piezo-photocatalysis. Its ability to enhance electron-hole separation while providing excellent fatigue resistance positions it as a promising candidate in this field. Defects were introduced to improve the structural polarization and photoelectrochemical properties of SBTO. SBTO nanocrystals, featuring a mixed structure of hierarchically ordered mesoporous microflowers and nanosheets, were successfully synthesized via the hydrothermal method. The SBTO sample synthesized at a lower hydrothermal temperature displayed optimal oxygen vacancy concentration and exhibited superior piezoelectric-photo synergistic degradation activity for organic pollutants. Additionally, corona polarization increases the macroscopic polarization of the SBTO photocatalyst, promoting the separation of photogenerated carriers. Finite element simulations confirmed that a single flower-like SBTO structure generates a higher piezoelectric potential compared to a sheet-like morphology. In conclusion, integrating self-assembled hierarchical structure design, ferroelectric polarization, and defect engineering forms an effective strategy for achieving high-performance SBTO-based layered perovskite piezo-photocatalysts.

Tuning CO2 Hydrogenation to Light Olefin Selectivity via Cu/Zn/Zr Supported on Modified SAPO‐34

AbstractTo alleviate CO2 emissions and reduce reliance on fossil fuels, a groundbreaking bifunctional catalyst system was introduced, which ingeniously merged CZZ with modified SAPO‐34 zeolite, to convert CO2 into light olefins. Different metals were impregnated into SAPO‐34 to form MeSAPO‐34 (Me = Zn, Zr, Mn) and the metal Zr content was altered. Furthermore, CZZ and MeSAPO‐34 was combined into CZZ/MeSAPO‐34 composite catalysts, which was used for CO2 hydrogenation. The MeSAPO‐34 and xZrSAPO‐34 catalysts were rigorously characterized by various techniques, revealing key physicochemical attributes. This innovative approach harnessed the synergistic effects between the metallic CZZ component and the modified zeolite to facilitate a series of reactions, effectively generating C2‐C4‐rich hydrocarbons. Benefiting from weak acid, higher oxygen vacancy concentration and interactions between components, the CZZ/ZrSAPO‐34 catalyst system has shown remarkable efficiency in enhancing the light olefin selectivity. The key aspects of this system are its ability to modulate surface acidity and oxygen vacancy concentration, thus creating favorable conditions for light olefin production via enhanced tandem reaction based on CO2 hydrogenation. This work enriches our insight into designing novel composite catalysts for promoting CO2 conversion and hence mitigating CO2 emissions.

Prediction of perovskite oxygen vacancies for oxygen electrocatalysis at different temperatures

Efficient catalysts are imperative to accelerate the slow oxygen reaction kinetics for the development of emerging electrochemical energy systems ranging from room-temperature alkaline water electrolysis to high-temperature ceramic fuel cells. In this work, we reveal the role of cationic inductive interactions in predetermining the oxygen vacancy concentrations of 235 cobalt-based and 200 iron-based perovskite catalysts at different temperatures, and this trend can be well predicted from machine learning techniques based on the cationic lattice environment, requiring no heavy computational and experimental inputs. Our results further show that the catalytic activity of the perovskites is strongly correlated with their oxygen vacancy concentration and operating temperatures. We then provide a machine learning-guided route for developing oxygen electrocatalysts suitable for operation at different temperatures with time efficiency and good prediction accuracy.

Improving the Nonvolatile Memory Characteristics of Sol-Gel-Processed Y2O3 RRAM Devices Using Mono-Ethanolamine Additives.

In this study, Y2O3-based resistive random-access memory (RRAM) devices with a mono-ethanolamine (MEA) stabilizer fabricated using the sol-gel process on indium tin oxide/glass substrates were investigated. The effects of MEA content on the structural, optical, chemical, and electrical characteristics were determined. As the MEA content increased, film thickness and crystallite size decreased. In particular, the increase in MEA content slightly decreased the oxygen vacancy concentration. The decreased film thickness decreased the physical distance for conductive filament formation, generating a strong electric field. However, owing to the lowest oxygen vacancy concentration, a large electrical field is required. To ensure data reliability, the endurance cycles across several devices were measured and presented statistically. Additionally, endurance performance improved with the increase in MEA content. Reduced oxygen vacancy concentration can successfully suppress the excess formation of the Ag conductive filament. This simplifies the transition from the high- to the low-resistance state and vice versa, thereby improving the endurance cycles of the RRAM devices.

Enhanced energy storage performance of 0.85BaTiO3–0.15Bi(Mg0.5Hf0.5)O3 films via synergistic effect of defect dipole and oxygen vacancy engineering

Dielectric capacitors are widely used in electronic devices due to their ultra-fast charge/discharge rate and ultra-high power density, but their lower energy density and poor thermal stability limit their further application. In contrast to the traditional strategy of suppressing defects, this work combines oxygen vacancies with defect dipoles to improve the breakdown strength and polarization behavior of ferroelectric films. Low concentration of oxygen vacancies and defect dipoles can trap charge carriers and increase breakdown strength, but if the concentration is too high, it can easily make films prone to breakdown. Moreover, the defect dipoles can reduce Pr by providing intrinsic restoring force for polarization switching, while excessive defect dipoles and oxygen vacancies can pin domain walls and increase Pr. By delicately controlling the concentration of oxygen vacancies and defect dipoles in the film, the BT-BMH film deposited at 0.135 mbar achieved the maximum breakdown strength and slim P-E loops, inducing the energy density to reach 108.9 J·cm-3 with an efficiency of 79.6 % at room temperature and excellent thermal stability in the wide temperature range of -100∼350 °C with the energy density of 69.1 J·cm-3. This work reveals the important significance of reasonable defect control for improving energy storage performance and provides an effective method for developing high-performance dielectric capacitors.