Lattice Oxygen Content Research Articles

Performance of Fe‐Mo Catalysts with Li/Na/K Promoters for Methanol Oxidation to Formaldehyde

Fe‐Mo catalysts are widely employed in the commercial oxidation of methanol to formaldehyde. This study investigates the influence of alkali metal promoters (Li, Na, and K) on the morphology, structure, surface properties, and catalytic performance of Fe‐Mo catalysts. The incorporation of alkali metal promoters was found to significantly modify the chemical composition and surface characteristics of the catalysts. Sodium and potassium promoters enhanced the formation of lamellar morphologies, promoted the segregation of molybdenum oxide crystals on the catalyst surface, and reduced the specific surface area. Additionally, they decreased the electron density around molybdenum atoms, lowered lattice oxygen content, and reduced catalytic activity. In contrast, lithium promoters suppressed lamellar morphology, facilitated the formation of a homogeneous cluster structure, and increased the concentration of bulk‐phase molybdenum oxide, thereby improving catalyst selectivity. Surface acidity analysis revealed that dimethyl ether, a by‐product, was predominantly formed on acidic sites. Optimization of lithium content further demonstrated that the catalyst achieved maximum formaldehyde selectivity at a Li/Mo molar ratio of 5%. These findings shed light on the role of alkali metal promoters in tailoring the properties of Fe‐Mo catalysts and offer valuable guidance for the design and optimization of advanced catalysts for methanol oxidation

Charge Transfer Effect in Layered CathodesThrough MEMS-Based In Situ TEM Studies.

The irreversible lattice oxygen release is the primary issue in layered oxide cathodes which is generally attributed to a consecutive phase transition with less lattice oxygen content. Herein, an anomalous metal segregation pathway is observed in oxygen vacancy defective layered cathodes, which happens far before the onset of phase transitions. The correlation of electron energy loss spectroscopy indicates that an early charge transfer from oxygen 2p to Mn 3d orbital is responsible. It further reveals a specific local vacancy heterogeneity that significantly lowers the migration barrier of Mn. This is further supported by the density functional theory simulations. In fact, the oxygen release is always initiated from the defective crystal, which alters the general degradation pathway initiated from the perfect crystal. This work shed light on the critical role of the local oxygen vacancy heterogeneity in the phase degradation of layered cathodes.

Phytic acid-assisted rapid electrochemical reconstruction for efficient oxygen evolution reaction at high current densities

The development of electrocatalysts for oxygen evolution reaction (OER) continues to be a critical bottleneck in the industrial production of hydrogen through water electrolysis. By activating lattice oxygen and surface reconstruction, it is feasible to create OER catalysts that are both highly efficient and stable. Herein, we synthesis Fe/Co-PA/NF (PA= Phytic Acid)electrocatalysts through a two-step in-situ liquid-phase method. The resulted Fe/Co-PA/NF catalyst demonstrated low overpotentials of 220 mV and 301 mV at current densities of 100 mA cm−2 and 1000 mA cm−2, respectively, in 1 M KOH solution. Comparative studies with CoFeO/NF electrocatalysts revealed that the introduction of phytic acid groups resulted in promoting surface reconstruction, thereby enhancing the overall electrocatalytic activity. Additionally, Fe/Co-PA/NF exhibited a stronger pH dependence during OER tests, indicating higher lattice oxygen content. This work proposes an effective method for developing high-performance electrocatalysts for oxygen evolution, emphasizing the potential of transition metals in large-scale hydrogen production through alkaline water electrolysis.

Understanding the Negative Apparent Activation Energy for Cu2O and CoO Oxidation Kinetics at High Temperature near Equilibrium

The pairs of Cu2O/CuO and CoO/Co3O4 as the carriers of transferring oxygen and storing heat are essential for the recently emerged high-temperature thermochemical energy storage (TCES) system. Reported research results of Cu2O and CoO oxidation kinetics show that the reaction rate near equilibrium decreases with the temperature, which leads to the negative activation energy obtained using the Arrhenius equation and apparent kinetics models. This study develops a first-principle-based theoretical model to analyze the Cu2O and CoO oxidation kinetics. In this model, the density functional theory (DFT) is adopted to determine the reaction pathways and to obtain the energy barriers of elementary reactions; then, the DFT results are introduced into the transition state theory (TST) to calculate the reaction rate constants; finally, a rate equation is developed to describe both the surface elemental reactions and the lattice oxygen concentration in a grain. The reaction mechanism obtained from DFT and kinetic rate constants obtained from TST are directly implemented into the rate equation to predict the oxidation kinetics of Cu2O without fitting experimental data. The accuracy of the developed theory is validated by experimental data obtained from the thermogravimetric analyzer (TGA). Comparing the developed theory with the traditional apparent models, the reasons why the latter cannot appropriately predict the true oxidation characteristics are explained. The reaction rate is jointly controlled by thermodynamics (reaction driving force) and kinetics (reaction rate constant). Without considering the effect of the reaction driving force, the negative apparent activation energy of Cu2O oxidation is obtained. However, for CoO oxidation, the negative apparent activation energy is still obtained although the effect of the reaction driving force is considered. According to the DFT results, the activation energy of the overall CoO oxidation reaction is negative, but the energy barriers of the elementary reactions are positive. Moreover, according to the first-principle-based rate equation theory, the pre-exponential factor in the kinetic model is dependent on the partition function ratio and decreases with the temperature for the Cu2O and CoO oxidation near equilibrium, which results in the apparent activation energy being slightly lower than the actual value.

Enhanced NOx-assisted soot combustion by cobalt doping to weaken mullite Mn-O bonds for lattice oxygen activation

Catalytic combustion is widely regarded as the most efficient technique for removing soot particulates from diesel engine exhaust, with its efficiency largely dependent on the performance of catalysts. In this study, a series of YMn1−xCoxO5-ζ catalysts were synthesized using a hydrothermal method to investigate their catalytic properties in soot oxidation. Among these catalysts, YMCo-0.2 exhibited the highest catalytic activity, achieving 90 % soot conversion at 392 °C and demonstrating robust tolerance in the presence of water vapor and SO2. Structural characterization revealed that Co doping did not alter the fundamental crystal structure of YMn2O5 mullite. Through some characterization comprehensive analysis, and DFT calculations further supported the experimental findings, indicate that Co substitution significantly increased the lattice oxygen mobility and surface active oxygen content. Compared to the surface lattice oxygens at other positions, the weakening of the Mn-O bond results in the lattice oxygens in the Co-O-Mn4+ sites in the catalysts exhibiting higher reactivity. Additionally, the catalyst displayed strong NO and O2 adsorption and activation capabilities, indicating its potential for efficient NOx-assisted soot combustion. This study provides insights for designing and optimizing mullite catalysts for soot combustion.

Manipulation of Mn/Ce ratio for deep chlorobenzene oxidation: Catalytic mechanisms and byproducts analysis

In this research, a sequence of spatial porous MnCeOx catalysts with varying Mn/Ce from 3:1 to 1:7 were synthesized using the sol–gel method for chlorobenzene (CB) oxidation. Mn1Ce1 exhibited the best performance due to its high lattice oxygen content and the strong interaction between Ce and Mn. The increase in Mn content in CeO2 catalysts resulted in enhanced redox properties and acidity, which was beneficial for the adsorption and activation of CB, thus enhancing the selectivity and the desorption of HCl on the catalyst surface. Carbon deposition and the formation of metal chloride were the main reasons for catalyst deactivation. At low temperature regions (150 ∼ 300 °C), insufficient oxidation capability and the chlorine deposition on the catalyst surface resulted in the formation of various chlorinated compounds. As the temperature increases (300 ∼ 450 °C), the release of HCl and more reactive oxygen species is available on the catalytic interface, generating various oxygen-containing degradation intermediates. This work proposed a fine-designed, low-cost mixed metal oxide catalysts for low temperature CB oxidation, and provided novel in-depth understandings of degradation intermediate formation thermodynamics. Our findings would be helpful for deep purification of chlorinated VOCs polluted industrial tail gas.

Effect of modified Ca-Al adsorbents on heavy metal fixation during co-combustion of coal and coconut shells: Experiments and simulations

As an alternative fuel, bio-waste coconut shells have shown promise in reducing pollution during the co-combustion process. In this study, a novel metal-mineral adsorbent, Ca-Al (Ca5Al6O14), was prepared and physically (ultrasonic) and chemically (ethylene glycol) modified to enhance its adsorption properties. Thermal adsorption experiments investigated the effect of the adsorbents on the fixation of six heavy metals (HMs): Cr, Cu, Mn, Ni, Pb, and Zn. XRD, SEM, BET, and XPS were used to analyze the adsorbents and the adsorption mechanism was investigated by combining lattice oxygen concentration and Factsage simulation calculations. The ecological risk assessment of heavy metals was used to comprehensively evaluate the fixation effects of the three Ca-Al adsorbents at different additive levels. The results showed that the modification significantly changed the morphological characteristics and oxygen activity of the Ca-Al adsorbents, increased the lattice oxygen and chemisorbed oxygen concentration, and laid the foundation for promoting the chemisorption process in the fixation of heavy metals. In combination with the Er (environmental risk factors), adding all three adsorbents reduced Ri (Risk index). Among them, Ca-Al (EG) at 3% had the best effect on Ri. 3% Ca–Al (EG) reduced the Er value of Ni by 49.02%. 5% Ca–Al (EG) reduced the Er value of Cr by 86.01%. 5% Ca–Al (UM) had the best effect on Mn, with a reduction of 46.13%. The addition of 10% Ca–Al (UM) reduced Er of Ni by 50.43%. Considering the practical application in coal-fired power plants, Ca-Al(EG), which exhibits a higher fixation rate at small additions, is more suitable.

High performance of PrMnO3 perovskite catalysts for low-temperature soot oxidation

In the field of heterogeneous catalysis for diesel vehicle exhaust, designing low-cost catalysts with high efficiency and low-temperature catalytic oxidation to reduce the ignition temperature of soot remains a significant challenge. In this study, a series of praseodymium manganese perovskites (PrMnO3) were synthesized using a solution combustion method that regulated the molar ratio of glycine to nitrate (φ). Notably, when φ = 1, the prepared catalyst (PMO-1) exhibited a multistage pore structure and large specific surface area, demonstrating excellent catalytic oxidation performance for soot (T10 = 280 °C, T50 = 377 °C, TOF=16.2 × 10-4 s−1, SCO₂ > 99 %) and NO (maximum NO conversion rate of 80 %). During soot combustion in a NO+O2 reaction atmosphere, the strong NO oxidation capacity of the catalyst provides sufficient NO2 as an oxidant for soot combustion, thereby further enhancing its oxidation performance (T50 = 360 °C). This study concludes that the excellent low-temperature catalytic oxidation performance of the PrMnO3 catalyst is attributed to the large specific surface area provided by its multistage pore structure and the extensive dispersion of active sites, which enhance the contact efficiency between soot particles and active sites. Additionally, based on multiple characterization results such as XPS, TOF calculations, and Soot-TPR, the PMO-1 catalyst exhibits a high content of lattice oxygen and efficient lattice oxygen migration. These properties further supply active oxygen for the NOx-assisted soot oxidation mechanism. This study offers a valuable, simple, and cost-effective strategy for designing perovskite catalysts and efficiently removing PM particles.

Nanoarchitectonics of hollow Co3O4 through tannic acid etching of ZIF-67 for catalysis of toluene oxidation

Oxide catalysts obtained by derivatization of MOFs as precursors often have excellent results in the catalysis of VOCs. In this study, the Co3O4 catalysts obtained by pyrolysis after tannic acid etching using ZIF-67 as precursor showed excellent toluene catalytic activity. Among them, Co3O4 −1–15 showed the best catalytic activity with T90 = 219 °C (the conversion temperatures of 90 %), which was 20 °C lower than that of Co3O4 -O obtained by direct pyrolysis of ZIF-67. It also exhibits excellent stability and cyclic stability. After tannic acid treatment, Co3O4 −1–15 exposed higher surface Co3+ and Olatt (surface lattice oxygen) content, which were the key factors for its most outstanding catalytic activity. Lattice oxygen mobility and oxygen vacancies were also important factors affecting catalyst activity.

The Role of Interfacial Interactions and Oxygen Vacancies in Tuning Magnetic Anisotropy in LaCrO3/LaMnO3 Heterostructures

AbstractThe interplay of lattice, electronic, and spin degrees of freedom at epitaxial complex oxide interfaces provides a route to tune their magnetic ground states. Unraveling the competing contributions is critical for tuning their functional properties. The relationship between magnetic ordering and magnetic anisotropy and the lattice symmetry, oxygen content, and film thickness in compressively strained LaMnO3 (LMO)/LaCrO3 (LCO) superlattices is investigated. Mn–O–Cr antiferromagnetic superexchange interactions across the heterointerface result in a net ferrimagnetic magnetic structure. Bulk magnetometry measurements reveal isotropic in‐plane magnetism for as‐grown oxygen‐deficient thin samples due to equal fractions of orthorhombic a+a‐c‐, and a‐a+c‐ twin domains. As the superlattice thickness is increased, in‐plane magnetic anisotropy emerges as the fraction of the a+a‐c‐ domain increases. On annealing in oxygen, the suppression of oxygen vacancies results in a contraction of the lattice volume, and an orthorhombic to rhombohedral transition leads to isotropic magnetism independent of the film thickness. The complex interactions are investigated using high‐resolution synchrotron diffraction and X‐ray absorption spectroscopy. These results highlight the role of the evolution of structural domains with film thickness, interfacial spin interactions, and oxygen‐vacancy‐induced structural phase transitions in tuning the magnetic properties of complex oxide heterostructures.

Structure and molecular-level transformation for oxidation of effluent organic matters by manganese oxides

As important organic components in water environments, effluent organic matters (EfOMs) from wastewater treatment plants are widely present in Mn-rich environments or engineered treatment systems. The redox interaction between manganese oxides (MnOx) and EfOMs can lead to their structural changes, which are crucial for ensuring the safety of water environments. Herein, the reactivities of MnOx with EfOMs were evaluated, and it was found that MnOx with high specific surface area, active high-valent manganese content and lattice oxygen content (i.e., amorphous MnO2) possessed stronger oxidizing ability towards EfOMs. Accompanying by EfOMs oxidation, Mn(IV) and Mn(III) were reduced into Mn(II), with Mn(III) as the significant active species. Through molecular-level transformation analysis by ultrahigh mass spectrometry (FT-ICR MS), the highly reactive compounds in EfOMs were clearly determined to be that with more aromatic and unsaturated structures, especially lignin-like compounds (the highest content in EfOMs (over 60 %)). EfOMs were oxidized by amorphous MnO2 into products with lower humification index (0.60 vs. 0.46), smaller apparent molecular weight (386.94 Da vs. 368.68 Da), and higher biodegradability (BOD5/COD: 0.12 vs. 0.78). This finding suggested that redox reactions between MnOx and EfOMs might alter their abiotic and biotic behaviors in receiving water environments.

Novel multineedle-to-cylinder plasma coupled with bimetallic catalysts for efficient removal of sulfides and ammonia in odor gases

Dielectric barrier discharge (DBD) plasma is a promising technology for treating odor gases. This study developed an innovative multineedle-to-cylinder (MC) configuration DBD plasma reactor and investigated its synergistic effect with bimetallic catalysts. The results demonstrated that MC-DBD plasma achieved complete elimination of ammonia and organic sulfides, while the removal efficiencies of inorganic H2S and CS2 reached 44.0 % and 53.0 % respectively. Compared with conventional plasma, the specific energy input (SEI) of MC-DBD was significantly reduced to 4.44 J/L. Furthermore, with the incorporation of Mn-Ce/ZSM-5 catalyst, optimal removal efficiencies of H2S and CS2 were significantly improved to 82.6 % and 90.7 %, and the SEI was reduced by 18 %. The electrical performance revealed that the low energy consumption was mainly attributed to stable fast-pulse micro-discharge channels and significantly enhanced inhomogeneous electric fields achieved by the filament discharge mode. Catalyst characterization (X-ray photoelectron spectroscopy and O2-temperature programming desorption) confirmed that surface catalytic reaction mainly follows the Mars-van Krevelen mechanism, where increased lattice oxygen content and the electron transfer between Mn and Ce play crucial roles in enhancing malodor degradation performance. This work proposes an efficient solution for degrading mixed malodors and provides an experimental and theoretical basis for optimizing plasma structure as well as researching treatment of mixed pollutants.

Boosting the removal of diesel soot particles by regulating the Pr−O strength over transition metal doped Pr6O11 catalysts

The content of active lattice oxygen and oxygen vacancies is crucial for the catalytic oxidation of soot. Herein, we adjust the Pr-O bond strength in Pr6O11 by doping several common transition metals (Mn, Fe, Co, Ni) to promote the formation of oxygen vacancies and the activation of lattice oxygen. This strategy does not compromise its crystal structure, allowing for improved catalytic performance while maintaining stability. The Mn-doped Pr6O11 catalyst shows the best soot catalytic oxidation performance. Its T50 (the temperature of soot conversion reaching 50 %) value is 396 °C under loose contact. Further characterizations and density functional theory (DFT) calculations demonstrate that PMO possesses a large specific surface area. Additionally, the weakening the strength of the Pr-O bond leaded to an increase in oxygen vacancies, which in turn enhanced the redox ability of catalyst. This work will provide a reference for the development of Pr-based catalysts for soot combustion.

Sepiolite-Supported Manganese Oxide as an Efficient Catalyst for Formaldehyde Oxidation: Performance and Mechanism.

The current study involved the preparation of a number of MnOx/Sep catalysts using the impregnation (MnOx/Sep-I), hydrothermal (MnOx/Sep-H), and precipitation (MnOx/Sep-P) methods. The MnOx/Sep catalysts that were produced were examined for their ability to catalytically oxidize formaldehyde (HCHO). Through the use of several technologies, including N2 adsorption-desorption, XRD, FTIR, TEM, H2-TPR, O2-TPD, CO2-TPD, and XPS, the function of MnOx in HCHO elimination was examined. The MnOx/Sep-H combination was shown to have superior catalytic activities, outstanding cycle stability, and long-term activity. It was also able to perform complete HCHO conversion at 85 °C with a high GHSV of 6000 mL/(g·h) and 50% humidity. Large specific surface area and pore size, a widely dispersed active component, a high percentage of Mn3+ species, and lattice oxygen concentration all suggested a potential reaction route for HCHO oxidation. This research produced a low-cost, highly effective catalyst for HCHO purification in indoor or industrial air environments.

Waste to wealth: Efficient wet desulfurization of electric arc furnace dust (EAFD) and recycling of desulfurization solid residue

In this study, we used calcined hazardous waste electric arc furnace dust (EAFD) as a desulfurizer for an effective wet desulfurization process. Testing for desulfurization efficacy revealed that the calcined EAFD, particularly when treated at 800 °C in an oxygen (O2) environment (termed EAFD-O2), achieved an unprecedented breakthrough sulfur capacity (BSC) of 3.71 gSO2·g−1 at 55 °C-the highest to date for EAFD applications in desulfurization efforts. Further investigation indicated that the calcination method expels certain volatile contaminants, thereby enhancing the crystallinity and lattice oxygen content of zinc oxide, the strong active phase of desulfurization in EAFD, which is principally responsible for the superior desulfurization results of EAFD-O2. Moreover, the observed reduction in the desulfurization slurry’s activity primarily stems from the depletion of the strong active phase of desulfurization (ZnO) and the resultant rise in the liquid phase’s sulfate concentration. Notably, the deactivated slurry’s solid residue predominantly consists of high-purity ZnFe2O4, a form of zinc ferrite utilized extensively for its proficiency in photocatalytic. Following straightforward processing, this substance displayed exceptional performance in photocatalytic-Fenton degradation tests on tetracycline (TC). In sum, the study not only turns hazardous EAFD into a powerful agent for removing SO2, a gaseous pollutant but also converts it into a value-added material, ZnFe2O4, thus proposing an integrated and efficient approach to solid waste management.

La‐Doped Mg‐Al Composite Oxides: Efficient Catalysts for the synthesis of Diethyl Carbonate via Transesterification of Ethylene Carbonate with Ethanol

AbstractSeries of La‐doped Mg−Al composite oxides were prepared by co‐precipitation method and used as catalysts for the synthesis of diethyl carbonate (DEC) via transesterification of ethylene carbonate (EC) with ethanol (EtOH). SEM, XRD, FT‐IR and XPS results confirmed that the introduction of La enhanced the interaction with MgO. The 8 mol % La‐doped Mg−Al composite oxide (calcined catalyst named HTC‐0.8 La) produced strong interactions and improved lattice oxygen content (27.84 %). Based on the N2 adsorption‐desorption and CO2‐TPD results, the HTC‐0.8 La catalysts possessed abundant multistage mesoporous structure, high strong base density and strength (0.941 mmol ⋅ g−1). Therefore, the HTC‐0.8La catalyst exhibited high catalytic activity with 58.5 % yield of DEC and 94.7 % selectivity to DEC (EC: EtOH molar ratio=1 : 6, reaction time=1.5 h, reaction temperature=150 °C and catalyst amount=3.2 wt %). Based on the correlation between catalytic activity and alkalinity, the yield of DEC was positively and linearly related to the strong alkali density of the catalyst. After five replicate experiments, the DEC yield after recovery and roasting reached 54.1 %, indicating that HTC‐0.8La is a renewable heterogeneous catalyst.

Influence of Y2O3 sintering aids on performance of c-BN-reinforced AlN/BN composite ceramics

AlN/h-BN composite ceramics exhibit considerable anisotropy, which significantly constrains their application in areas such as semiconductor packaging and light-emitting diodes. The introduction of c-BN can significantly enhance mechanical properties and effectively reduce the anisotropy. However, this results in lower thermal conductivity, which is important issue that needs to be addressed. In this study, hot-press sintering was employed to fabricate AlN-10 wt% h-BN-15 wt% c-BN-x wt.% Y2O3 (AB15CxY, with x = 0, 1, 2, 3, 4) composite ceramics. Effects of Y2O3 content on microstructure, anisotropy, thermal conductivity, and flexural strength of AlN/BN composite ceramics were systematically investigated. Results indicate that during high-temperature sintering, c-BN undergoes phase transformation into "onion-like'' h-BN, and Y2O3 reacts with Al2O3 film on the surface of AlN powder to form Y3Al5O12 (YAG) phase. YAG phase promotes sintering densification as well as directional arrangement of lamellar h-BN, endowing composite ceramics with relative density of 99.6 % (sample AB15C1Y) with increased degree of anisotropy (the index of orientation preference is |IOP| = 68–93). Thermal conductivity of AlN/BN composite ceramics is directly correlated with lattice oxygen content, and as Y2O3 content increases, lattice oxygen content decreases monotonically. Lattice oxygen content of sample AB15C3Y is as low as 0.35 wt%, and the maximum values of K∥ and K⊥ are 100 and 59 W‧m−1‧K−1, respectively, which represent increases of 64.8 % and 51.3 % compared with those of AB15C0Y ceramic, respectively. With the increase in Y2O3 content, AlN grains become gradually larger, and the proportion of YAG phase, which is characterized by brittle grain boundaries, increases, leading to gradual reduction in the flexural strength of AlN/BN composite ceramics.

Constructing Efficient CuO-Based CO Oxidation Catalysts with Large Specific Surface Area Mesoporous CeO2 Nanosphere Support.

CeO2 is an outstanding support commonly used for the CuO-based CO oxidation catalysts due to its excellent redox property and oxygen storage-release property. However, the inherently small specific surface area of CeO2 support restricts the further enhancement of its catalytic performance. In this work, the novel mesoporous CeO2 nanosphere with a large specific surface area (~190.4 m2/g) was facilely synthesized by the improved hydrothermal method. The large specific surface area of mesoporous CeO2 nanosphere could be successfully maintained even at high temperatures up to 500 °C, exhibiting excellent thermal stability. Then, a series of CuO-based CO oxidation catalysts were prepared with the mesoporous CeO2 nanosphere as the support. The large surface area of the mesoporous CeO2 nanosphere support could greatly promote the dispersion of CuO active sites. The effects of the CuO loading amount, the calcination temperature, mesostructure, and redox property on the performances of CO oxidation were systematically investigated. It was found that high Cu+ concentration and lattice oxygen content in mesoporous CuO/CeO2 nanosphere catalysts greatly contributed to enhancing the performances of CO oxidation. Therefore, the present mesoporous CeO2 nanosphere with its large specific surface area was considered a promising support for advanced CO oxidation and even other industrial catalysts.

Electrothermal toluene oxidation by utilizing Joule heat from Pd/FeCrAl electrified metallic monolith catalyst

An electrified metallic monolith catalyst of direct growing palladium active component on FeCrAl strip substrate (Pd/FeCrAl) via an in-situ nucleation and plating process was prepared, and investigated in a special electrothermal toluene oxidation (ETO) mode reaction by direct connecting to an electric power supply for the internal Joule heating. This ETO reaction mode could promote the Pd/FeCrAl catalyst to achieve 90 % toluene conversion at much lower reaction temperature of 103 °C under an input current of 3.0 A, and greatly reduce the energy consumption more than 50 times, well beyond the performance of catalyst in the conventional toluene oxidation mode reaction. And the intimate contact of FeCrAl substrate and Pd active layer in catalyst is favorable for the convenient electron transfer between electric power supply and reaction active sites, which can significantly enhance the content and electron transformation of lattice oxygen, and the synergistic effect of Pd0-PdO active sites.

Effect of Er2O3/MgO ratio on mechanical and thermal properties of Si3N4 ceramics

AbstractSi3N4 ceramics with high mechanical properties and thermal conductivity, exhibiting fine and bimodal microstructure, were prepared by adjusting the Er2O3/MgO ratio and hot‐pressing sintering at 1800°C for 4 h. The microstructure, grain distribution, lattice oxygen content, mechanical properties, and crack propagation process of the sintered bulk samples were systematically investigated. It was found that a low Er2O3/MgO ratio contributed to the densification of Si3N4 ceramics, whereas a high Er2O3/MgO ratio favored the grain growth of Si3N4 ceramics. In this research, the grain size distribution and average diameters as well as their impact on mechanical properties were examined. When the ratio of Er2O3/MgO was 3:1, Si3N4 had a larger average diameter and higher thermal conductivity, but the mechanical properties were somewhat reduced. When the ratio of Er2O3/MgO was 2:2, the sample displayed enhanced mechanical performance, which can be explained by the formation of a bimodal structure. The research indicates that it is feasible to control the microstructure and optimize the mechanical properties of Si3N4 ceramics by tailoring the sintering additives.