Fe-based Oxides Research Articles

Structural evolution of mechanically alloyed ODS steel powders during ball milling and subsequent annealing treatment

In the present work, a novel 9Cr oxide-dispersion strengthened (ODS) steel powders with Y2O3 (0.5 wt%) dispersoids were synthesized by high planetary ball milling at different time intervals (2, 8, and 16 hours). The structural and crystallographical evolution of the produced powders during the ball milling and post-annealing treatment were evaluated by SEM, XRD, and micro-Vickers hardness analyses. The SEM results showed that the fine dispersions of powders were achieved with the extending milling time. When milling time was 8h, it was observed that the mean size of powders increased maximum level of 101 μm and then dramatically reduced to 5 μm at latest milling time (16h). The XRD data revealed that the crystallite size of ODS powders diminished gradually with increasing milling time. Plus, all reflection peaks of the Fe, Cr, W, Mo expanded and the diffraction peaks of the Y2O3, W progressively disappeared with the increasing milling time. The hardness results revealed that the increasing milling time was beneficial for hardness improvement, due to dominant strain hardening mechanism and it developed from 160 to 334 Hv after 16h of milling protocol. To understand high temperatures characteristics such as grain growth, phase transformation, and hardness of produced powders, 16h milled powders subjected to post-annealing treatments at 700 oC and 900 oC for 1 h. When pure Fe and Cr peaks were observed in the non-annealed powders, no evident reflection peak of Y2O3 was observed. However, all pure Fe and Cr reflection peaks became narrower and Y2O3 reflection exhibited more sharper tendency with increased annealing temperatures, which resulted in increased grain growth and formation of Fe-based oxide structures.

A-site deficient Fe-based double perovskite oxides PrxBaFe2O5+δ as cathodes for solid oxide fuel cells

In this work, Pr-deficiency is presented here as an effective strategy to promote the electrochemical properties of Pr x BaFe 2 O 5+δ (Pr x BF, x = 1.00, 0.97, 0.93, 0.90) cathodes for solid oxide fuel cell (SOFC). The Pr x BF cathode materials were prepared by a sol-gel method. The crystal structure results show that the Pr x BF (x = 1.00) is double-perovskite phase with orthorhombic structure and the Pr x BF (x = 0.97, 0.93, 0.90) is tetragonal perovskite structure. Introduction of Pr-deficiency in Pr x BF oxides causes the decrease of oxygen content. The average TEC values (30–850 °C) for Pr x BF are mainly concentrated between 15.29 and 15.95 × 10 −6 K −1 . In comparison to the parent PrBaFe 2 O 5+δ oxides, the Pr-deficiency cathodes significantly enhance the electrochemical catalytic activity while maintain the lower thermal expansion coefficient. Among the series of Pr x BF cathodes, the Pr 0.93 BF sample obtains the lowest polarization resistance. The fitted result of impedance spectra for Pr 0.93 BF cathode indicates that the charge transfer process in the high frequency plays a more dominant role in the oxygen reduction reaction. Furthermore, the Pr 0.93 BF electrode exhibits a good tolerance to CO 2 . The power density of an anode supported single cell with Pr 0.93 BF cathode achieved 967 mW cm −2 at 700 °C. Preliminary results suggest that Pr x BF oxides are expected to be promising candidates for cathode in SOFC. • The Pr x BaFe 2 O 5+δ (Pr x BF) cathode materials were synthesized by a sol-gel method. • The TEC values of P x BF are concentrated between 15.29 and 15.95 × 10 −6 K −1 . • The Pr 0.93 BF sample shows the lowest polarization resistance. • The peak power densities of Pr 0.93 BF cathode are 967 mW cm −2 at 700 °C.

Correlation between the Cation Disorders of Fe3+ and Li+ in P3-Type Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2 for Sodium Ion Batteries.

Various Fe-based layered oxide materials have received attention as promising cathode materials for sodium ion batteries because of their low cost and high specific capacity. Only a few P3-type Fe-based oxide materials, however, have been examined as cathodes because the synthesis of highly crystalline P3-type Fe-based oxides is not facile. For this reason, the structural merits of the P3 structure are not yet fully understood. Herein, highly crystalline P3-type Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2 heated at 900 °C is introduced to improve the electrochemical performance of Fe-based layered oxides. The structures, reaction mechanisms, and electrochemical performances of P3 Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2, P2 Na0.57[Li0.1(Fe0.5Mn0.5)0.9]O2, and P2 Na0.67[Fe0.5Mn0.5]O2 are compared to demonstrate the roles of Li+ doping in the improved electrochemical performance of P3 Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2, such as stable capacity retention over 100 cycles. P3 Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2 significantly suppresses the migration of Fe3+ ions to tetrahedral sites in the Na layer during cycling because the cation disorder of Li+ is more favorable than that of Fe3+. As a result, P3 Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2 shows better cycle performance than P2 Na0.67[Fe0.5Mn0.5]O2. P3 Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2 also exhibits an improved rate performance compared to P2 Na0.67[Fe0.5Mn0.5]O2. This finding provides fundamental insights to improve the electrochemical performance of layered oxide cathode materials for sodium ion batteries.

Progress on Fe-Based Polyanionic Oxide Cathodes Materials toward Grid-Scale Energy Storage for Sodium-Ion Batteries.

The development of large-scale energy storage systems (EESs) is pivotal for applying intermittent renewable energy sources such as solar energy and wind energy. Lithium-ion batteries with LiFePO4 cathode have been explored in the integrated wind and solar power EESs, due to their long cycle life, safety, and low cost of Fe. Considering the penurious reserve and regional distribution of lithium resources, the Fe-based sodium-ion battery cathodes with earth-abundant elements, environmental friendliness, and safety appear to be the better substitutes in impending grid-scale energy storage. Compared to the transition metal oxide and Prussian blue analogs, the Fe-based polyanionic oxide cathodes possess high thermal stability, ultra-long cycle life, and adjustable voltage, which is more commercially viable in the future. This review summarizes the research progress of single Fe-based polyanionic and mixed polyanionic oxide cathodes for the potential sodium-ion batteries EESs candidates. In detail, the synthesized method, crystal structure, electrochemical properties, bottlenecks, and optimization method of Fe-based polyanionic oxide cathodes are discussed systematically. The insights presented in this review may serve as a guideline for designing and optimizing Fe-based polyanionic oxide cathodes for coming commercial sodium-ion batteries EESs.

Enhanced Performance of La0.8Sr0.2FeO3-δ-Gd0.2Ce0.8O2-δ Cathode for Solid Oxide Fuel Cells by Surface Modification with BaCO3 Nanoparticles.

Recently, Fe-based perovskite oxides, such as Ln1-xSrxFeO3-δ (Ln = La, Pr, Nd, Sm, Eu) have been proposed as potential alternative electrode materials for solid oxide fuel cells (SOFCs), due to their good phase stability, electrocatalytic activity, and low cost. This work presents the catalytic effect of BaCO3 nanoparticles modified on a cobalt-free La0.8Sr0.2FeO3-δ-Gd0.2Ce0.8O2-δ (LSF-GDC) composite cathode at an intermediate-temperature (IT)-SOFC. An electrochemical conductivity relaxation investigation (ECR) shows that the Kchem value of the modified LSF-GDC improves up to a factor of 17.47, demonstrating that the oxygen reduction process is effectively enhanced after surface impregnation by BaCO3. The area-specific resistance (ASR) of the LSF-GDC cathode, modified with 9.12 wt.% BaCO3, is 0.1 Ω.cm2 at 750 °C, which is about 2.2 times lower than that of the bare cathode (0.22 Ω.cm2). As a result, the anode-supported single cells, with the modified LSF-GDC cathode, deliver a high peak power density of 993 mW/cm2 at 750 °C, about 39.5% higher than that of the bare cell (712 mW/cm2). The single cells based on the modified cathode also displayed good performance stability for about 100 h at 700 °C. This study demonstrates the effectiveness of BaCO3 nanoparticles for improving the performance of IT-SOFC cathode materials.

Synergistic modulation of inverse spinel Fe3O4 by doping with chromium and nitrogen for efficient electrocatalytic water splitting

Earth-abundant Fe-based oxides have drawn less attention in electrocatalytic water splitting owing to the inferior intrinsic activity and poor conductivity. Therefore, developing an effective method to increase the catalytic performance of Fe-based oxides is of great importance for the practical application. Herein, a novel Cr/N co-doped Fe3O4 electrocatalyst (denoted as Cr-Fe3O4-N/NF) is designed and prepared by a simple immersion treatment followed by a calcination method for efficient water splitting. The resultant Cr-Fe3O4-N/NF shows significant catalytic activity for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with overpotentials of 218 and 95 mV at 10 mA cm–2. Furthermore, the water splitting system using Cr-Fe3O4-N/NF could afford a current density of 10 mA cm–2 at 1.53 V, which is superior to two-electrode system composed of Pt/C and RuO2. The high activities are attributed to the synergistic effect between Cr and N element doping. Specifically, the introduction of electron-deficient Cr is conductive to accelerate the dissociation process of water, adsorption process of intermediates, adjust the electronic structure. Simultaneously, N doping can increase the adsorption of H intermediates, provide more active sites for hydrogen absorption, and improve the electrical conductivity. This study provides a new strategy for Cr and N co-doped metal oxides electrocatalysts for high-performance water splitting.

Sensitive detection of As(III) on Fe3O4/MoS2 through interfacial engineering to accelerate the Fe2+/Fe3+ cycle: Identifying the dominant role of electron transfer induced by valence change in synergistic electroanalysis

Fe-based metal oxide nanomaterials have attracted significant attention as the electroanalytical sensing for heavy metal ions (HMIs) detection. It is recently found that their activities should be mainly ascribed to their valance change behavior (i.e. the Fe2+/Fe3+ cycle). However, how to promote the Fe2+/Fe3+ cycle to further increase their detection performance is highly desired yet challenging. Herein, the nanocomposite of Fe3O4/MoS2 is developed as a sensing for the electrochemical detection of the highly toxic As(III). Through a series of characterizations including the XPS and DFT, the Fe3O4/MoS2 shows an accelerated electron transfer induced by the valence change of Fe2+/Fe3+ cycle. The active Mo4+ on MoS2 can serve as electron doner to reduce the Fe3+ to Fe2+ on Fe3O4, and thus promotes the Fe2+/Fe3+ cycle. Moreover, the synergistic effect between the excellent adsorption ability of Fe3O4 towards As(III) and the good conductivity of MoS2 will further benefit to the detection. As expected, the Fe3O4/MoS2 reflects an outstanding detection performance to As(III) with a sensitivity of 4.16 μA•ppb–1, which even much outperforms than that of noble-metal materials. Overall, these discoveries are expected to drive great advances in the application of the accelerated valence change behavior for electroanalysis.

Coal-direct chemical looping hydrogen generation with BaMnO3 perovskite oxygen carrier

Coal-direct chemical looping hydrogen generation (CDCLHG) is a novel process that uses coal to directly produce H2 with inherent CO2 capture. A key issue is to find out suitable oxygen carriers for this process. In this study, perovskite was proposed as the oxygen carrier for CDCLHG, and a series of Mn-based and Fe-based perovskite oxides were synthesized by a sol-gel method for CDCLHG reactions in a fixed-bed reactor. The results showed that BaMnO3 was an optimal oxygen carrier for CDCLHG, which could obtain H2-rich gas (>85%) with a high H2 gas production rate, about 13 times higher than that in char steam gasification. Further tests showed that the optimal reaction temperature and O/C ratio were 850 °C and 1: 0.05, respectively. XRD and XPS patterns indicated that part of the lattice oxygen in BaMnO3 could convert to the carbonate oxygen in BaCO3 during the fuel oxidation stage (FO stage) and obtained BaMnO3-δ with plentiful oxygen vacancies in it. The BaMnO3-δ could partially restore its lattice oxygen in the reduction of steam stage (RS stage) and completely recover its initial structure in the air calcining stage (AC stage). SEM images showed that the decrease of BaMnO3 reaction performance after 9 cycles was mainly due to ash accumulation.

Catalytic oxidation of chlorinated aromatics over Fe-based oxide catalysts modified by Mn

FexMny mixed oxide catalysts prepared by co-precipitation method are applied in catalytic combustion of chlorobenzene (CB) and 1,2-dichlorobenzene (1,2-DCB). Characterization shows that Mn species of Fe9Mn1highly disperse into α-Fe2O3 as Fe-O-Mn structure. With the increase in Mn content, a part of Mn is separated as MnO2 and α-Mn2O3. Fe-O-Mn structure greatly increases the acidity (especially for strong acid) and reducibility of α-Fe2O3. In CB and 1,2-DCB oxidations, FexMny catalysts are active, of which Fe9Mn1 catalyst presents the highest activity. At 5% – 20% O2 and 500 – 2000 ppm 1,2-DCB at space velocity of 15,000 mL g-1h−1, the apparent rates at 300 °C over Fe9Mn1 are estimated to be 0.056 – 0.112 μmol min−1 m−2, and the temperatures needed for 50% and 90% conversions are 294 – 342 °C and 346 – 375 °C, respectively. High availabilities of surface oxygen and acid sites are related to effective Cl removal in aid of active hydroxyls produced during the reaction (confirmed by in situ FT-IR tests), which are responsible for high activity of Fe9Mn1 catalyst. For the catalysts with MnO2 and Mn2O3 domains on the surface, Cl strong adsorption results in their deactivation. Moreover, Fe9Mn1 catalyst shows high stability at 350 °C on feed stream containing 1000 ppm 1,2-DCB within 600 min duration or for five runs. The selectivity for CO/CO2 approaches 98% or higher and no chlorination products are detected within FID limitation (1 ppm) under the above mentioned broad reaction conditions, which are highly desirable for industrial application.

Synergistically improving electrocatalytic performance and CO2 tolerance of Fe-based cathode catalysts for solid oxide fuel cells

Fe-based pervoskite oxides Bi0.5Sr0.5Fe1−xZrxO3−δ (BSFZx, x = 0, 0.05, 0.10 and 0.15) were synthesized and developed by doping of cation Zr as possible cathodes for solid oxide fuel cells (SOFCs). Herein, we carefully investigated the effect of Zr-doped on BSFZx physicochemical property. The Bi0.5Sr0.5Fe0.90Zr0.10O3−δ (BSFZ0.10) cathode shows the lowest Rp values ranging from 0.52 to 0.11 Ω cm2 in the temperature range of 600–700 °C and the corresponding activation energy is about 1.135 eV. A single fuel cell with BSFZ0.10 cathode delivers a satisfactory electrocatalytic performance with a peak power density (PPD) as high as 1.2 W cm−2 at 700 °C. The BSFZ0.10 also exhibits unsurpassed stability by less change in Rp values under different CO2concentrations (5, 10 and 15 vol%). The excellent chemical stability and CO2 tolerance of BSFZx electrode material is mainly due to the doping of highly acidic Zr4+ and the increase of average metal bond energy (ABE). The present work highlights that BSFZx oxides are very promising candidate cathode catalysts for oxygen-conducting SOFCs.

Boosting oxygen evolution over inverse spinel Fe-Co-Mn oxide nanocubes through electronic structure engineering

• Mn 0.5 Co 0.5 Fe 2 O 4 nanocubes exhibit high oxygen evolution activity. • The optimized d -band center offers a balanced adsorption strength of *OOH. • Fe-based oxides were synthesized through a thermal decomposition process. Fossil fuels are urgent to be replaced with renewable energies to achieve carbon neutrality. Intermittent renewable energies such as solar and wind could be stored in chemical bonds, such as hydrogen and carbon-containing chemicals through water and CO 2 electrolyzers respectively. Those two energy systems share a common anodic reaction, the sluggish oxygen evolution reaction (OER), which currently relies on precious noble metals to achieve a reasonable energy conversion efficiency. Herein, tuning the d- band center of Fe-based inverse spinel oxides has been achieved through compositions and morphologies engineering. Ternary Mn 0.5 Co 0.5 Fe 2 O 4 nanocubes exhibit oxygen evolution activity superior to the benchmark RuO 2 . Mössbauer and in-situ infrared spectra combined with density functional theory calculations prove that the optimized d -band center offers a balanced adsorption strength of intermediate *OOH on Mn 0.5 Co 0.5 Fe 2 O 4 nanocubes. This work provides a promising approach to the design and synthesis of highly efficient electrocatalysts beyond oxygen evolution.

Surface Si decoration of ultrafine NaFeMn-Si catalyst enabling high Fe-phase electron density for effectively converting syngas to aromatics

• Preparing NaFeMn-Si catalyst with ultrafine crystals through Si modification. • Improving Fe phase electron density by decoration of Na 2 SiO 3 on crystal surface. • Promoting olefin to paraffin ratio to reduce by-product via high electron density. • Achieving 90% conversion with 64% aromatic selectivity under optimal condition. Effectively converting syngas to aromatics attracts widespread attention for its potential value in alleviating the scarcity of oil resources, while the promising catalysts composited with Fe-based oxides and zeolites are typically plagued by lower aromatics selectivity. Herein, ultrafine NaFeMn-Si catalyst is designed via the surface decoration of SiO 2 -Na 2 SiO 3 on the crystal surface by a unique post-modification strategy. Experiments and calculations demonstrate that surface decoration of Si reduces the NaFeMn-Si crystal size to 6.7 nm by potently preventing agglomeration, which greatly enlarges the active surface area to promote the catalytic activity. Moreover, the in situ formed surface Na 2 SiO 3 , which is converted from Na 2 O under the synergism between Si and Na species, remarkably weakens binding force of –SiO 3 in comparison with –O bond. Thereby, the electron delocalization of Na is enhanced by releasing the outer electron to Fe, significantly increasing the electron density of Fe phase. This elaborate modification strategy effectively modulates the adsorption and dissociation of H 2 and CO molecules, which facilitates the formation of iron carbide as the active center, not only improving the intermediary olefin/paraffin ratio to achieve a superior catalytic performance of 64% aromatic selectivity with 90% CO conversion, but also providing an appealing and instructive design guidance for the aromatics synthesis over Fe-based composite catalysts.

Designing a durable high-rate K0.45Ni0.1Fe0.1Mn0.8O2 cathode for K-ion batteries: A joint study of theory and experiment

K-ion batteries (KIBs) hold great promise for large-scale energy storage. However, the absence of suitable cathode materials limits their practical application. Meanwhile, rationally designing advanced cathode materials for KIBs remains an open question. In this work, based on density functional theory calculations, we find that the bond stability of Fe−O is higher than that of Co−O in layered transitional metal (TM) oxides. Additionally, the K-ion migration in the Fe-based layered TM oxide has a significantly lower activation energy barrier than that in the Co-based one. Based on this theoretical prediction, we successfully synthesized a low-cost K0.45Ni0.1Fe0.1Mn0.8O2 cathode, which shows excellent structural stability and superior K-storage properties, including durable cycle life and high-rate capability. Moreover, the designed K0.45Ni0.1Fe0.1Mn0.8O2 cathode possesses a great full-cell performance with a discharge capacity of ∼75 mA h g−1 and capacity retention of ∼80% after 100 cycles. The results show that Fe has better structural stability and K-ion diffusion than high-cost Co in layered oxide cathodes, and this finding provides new insights into the design of low-cost and high-performance KIB layered cathodes. This work highlights the feasibility of a theory-guided experiment in screening promising battery materials.

Influence of Zn Injection on Corrosion of 304SS Under PWR Primary Side Conditions

The structural materials in nuclear power plants experience corrosion under high temperature water chemistry environments, which could result in serious safety issues. Zinc injection to the primary side chemistry has been demonstrated to reduce corrosion rate of the structural materials and radiation dose rate by modifying the oxide film formed on the structural materials. The purpose of this work is to investigate the effect of Zn addition at different concentrations on 304SS under PWR primary side conditions by SEM, GIXRD, Raman spectrum, XPS, electrochemical method and thermodynamic calculation. When Zn concentration is increased, the number and size of Fe-based spinel oxide particles in the outer layer decreases while Cr-based spinel oxide in the inner layer remains unchanged. The corrosion current density of 304SS and defect density of the oxide film decrease with increasing Zn concentration. These results conclude that corrosion resistance of 304SS is enhanced in the presence of Zn. In addition, the thermodynamic analyses on the spinel oxides of surface were performed and the results are in good agreement with the experimental observations presented in this work.

Based on the utilization of jarosite residue: The lithium storage performance of α-Fe2O3 materials synthesized from different iron solution systems

• The anion in iron salt has a great impact on the morphology of the prepared α -Fe 2 O 3 . • α -Fe 2 O 3 prepared from sulfate has a high capacity but large fluctuations. • α -Fe 2 O 3 prepared from chloride shows a low capacity but good cycling stability. In this work, three kinds of iron simulation solution systems (FeCl 3 , FeSO 4 , and Fe 2 (SO 4 ) 3 solutions) are prepared and used as an iron source for synthesizing α -Fe 2 O 3 electrode materials by the one-step sucrose-assisted thermal decomposition method. The microstructure and lithium storage performance of the as-prepared α -Fe 2 O 3 materials are systematically studied by XRD, SEM, TGA, FT-IR, XPS, CV, EIS, and discharge/charge measurements. The results demonstrate that the α -Fe 2 O 3 samples prepared from FeSO 4 simulation solution or Fe 2 (SO 4 ) 3 simulation solution are composed of interconnected nanorods particles and contain a certain amount of undecomposed SO 4 2− ; while the α -Fe 2 O 3 sample prepared from FeCl 3 simulation shows irregular particle morphology (with the size ranging from hundreds of nanometers to several microns) and contains a small amount of Cl − . The two α -Fe 2 O 3 samples prepared from sulfate simulation solution exhibit high lithium storage activity but experience large capacity fluctuation during cycling. In contrast, the α -Fe 2 O 3 sample prepared from the FeCl 3 simulation solution gives a lower reversible capacity but much better cycling stability. After 400 cycles at 500 mA g −1 , the α -Fe 2 O 3 samples prepared from FeSO 4 , Fe 2 (SO 4 ) 3 , and FeCl 3 simulation solutions deliver reversible capacities of 947, 1071, and 628 mA h g −1 , respectively. The results reported in this work could provide clues for the structural design and performance modification of Fe-based oxides as anode materials for lithium-ion batteries.

Polyaniline coating enables electronic structure engineering in Fe3O4 to promote alkaline oxygen evolution reaction

The electronic structure of active sites is of importance for catalysts to achieve an optimized interaction with the intermediates. In this study, a unique organic–inorganic hybrid oxygen evolution reaction electrocatalyst composed of electrochemically inactive conducting polyaniline (PANI) and non-precious Fe-based oxide Fe3O4 is presented. PANI molecules were in situ loaded on Fe3O4 nanoparticles through an efficient and simple process under mild conditions. The electronic structure of Fe3O4 was modulated by creating a strong interaction with PANI molecules, leading to enhanced activity and stability of the catalyst to achieve 10 mA cm−2 geometrical current density at overpotential of 265 mV in 1 M aqueous KOH solution. This work demonstrates that a highly efficient electrocatalyst can be achieved by molecular modification and provides a novel strategy for the optimization of the inactive non-precious catalysts.

In situ encapsulation of iron oxide nanoparticles into nitrogen-doped carbon nanotubes as anodic electrode materials of lithium ion batteries.

Fe-based oxides are considered as promising anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacities, low cost, natural abundance and environmental friendliness. However, their severe volume expansion upon cycling and poor conductivity limit their cycling stability and rate capability. To address this issue, a hybrid of Fe2O3 nanoparticles encapsulated at the endpoints of nitrogen-doped CNTs (Fe2O3@NCNTs) is designed and prepared using a metal-catalyzed graphitization-nitridization driven tip-growth process and subsequent oxidation in air. When evaluated as an anode material for LIBs, this Fe2O3@NCNT hybrid exhibits a high capacity of 1145 mA h g-1 at 100 mA g-1, excellent rate capability of 907 mA h g-1 at 5.0 A g-1 and remarkable cycling stability of 856 mA h g-1 after 800 cycles at 1 A g-1, which are much superior to those of the Fe2O3/carbon black (CB) control material. The outstanding electrochemical performance benefits from the unique nanoarchitecture of Fe2O3@NCNTs, which provides a porous conductive matrix for effective electron-ion transport, and provides space confining carbon nanocaps as well as stress buffer nanocavities for robust structural stability during the lithiation/delithiation process. The results may pave the way for the rational structural design of high-performance metal oxide-based anode materials for next-generation LIBs.

K-Edge XANES Investigation of Fe-Based Oxides by Density Functional Theory Calculations

K-Edge XANES Investigation of Fe-Based Oxides by Density Functional Theory Calculations

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

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

Conductive substrates-based component tailoring via thermal conversion of metal organic framework for enhanced microwave absorption performances

Component tailoring, especially for the conductive substrates-based composites, acts as a significant role in optimizing the electromagnetic (EM) parameters and improving the EM response capability. Here, Fe-based metal oxides modified rGO microwave absorbers with component evolution were fabricated through hydrothermal treatment and subsequent pyrolysis process. The synergistic effects of the dielectric loss (multi-relaxations) and the magnetic loss (resonance and eddy current) are found to be effective in promoting the microwave absorption property of Fex-1Ox/C/rGO absorbers. As the thermal treatment temperature reaches 500 °C, the as-prepared composite sample shows ideal microwave absorption performance, where the reflection loss value is −25.94 dB, and the effective bandwidth reaches 5.84 GHz at 1.9 mm. In addition, CST simulation was employed to analyze the microwave absorption capability in the actual far field. When the scattering angle is 0° and 20°, the radar cross section (RCS) reduction of S-500/PEC layers is 8.11 dB m2 and 8.80 dB m2, respectively. This study exhibits the importance of component tailoring in enhancing the performances of substrates-based microwave absorption materials.