Manganese-rich SmBaCo2−x−yMnxMgyO5+δ (x = 0.5, 1, 1.5 and y = 0.05, 0.1) with stable structure and low thermal expansion coefficient as cathode materials for IT-SOFCs

SmBaCo_2−x−yMn_xMg_yO_5+δ (x = 0.5, 1, 1.5 and y = 0.05, 0.1) samples are synthesized by sol-gel method. The influence of different substitution of Mn and Mg for Co on crystal structures, thermal expansion coefficient (TEC), electrical conductivities and electrochemical performances have been investigated. The generation of the secondary phase BaMnO₃ is suppressed with Mg²⁺ increasing. Demonstrated by temperature-dependent X-ray diffraction from 25 °C to 700 °C, the structure of SmBaCo_0.4Mn_1.5Mg_0.1O_5+δ in high temperature is stable. The TEC of SmBaCo_1.45Mn_0.5Mg_0.05O_5+δ, SmBaCo_0.95MnMg_0.05O_5+δ, SmBaCo_0.45Mn_1.5Mg_0.05O_5+δ and SmBaCo_0.4Mn_1.5Mg_0.1O_5+δ are 15.77 × 10⁻⁶ K⁻¹, 16.20 × 10⁻⁶ K⁻¹, 12.19 × 10⁻⁶ K⁻¹ and 12.58 × 10⁻⁶ K⁻¹, respectively, which are much lower than those of cobalt-based layered perovskites and more compatible with the thermal expansion of SDC electrolyte. Although the electrochemical performances of SmBaCo_2−x−yMn_xMg_yO_5+δ (x = 0.5, 1, 1.5 and y = 0.05, 0.1) decrease slightly with Mn increasing, the polarization resistances of the SmBaCo_1.45Mn_0.5Mg_0.05O_5+δ and SmBaCo_0.4Mn_1.5Mg_0.1O_5+δ are 0.17 Ω cm² and 0.30 Ω cm² at 800 °C, respectively, which can meet the electrochemical performance requirements of cathode materials. Among the samples, the SmBaCo_1.45Mn_0.5Mg_0.05O_5+δ and SmBaCo_0.4Mn_1.5Mg_0.1O_5+δ show better tradeoff properties between TEC and electrochemical performance as cathode materials for IT-SOFCs.     

Preparation and dielectric properties of (Sr1−xCax)Fe0.5Nb0.5O3; (x=0.0, 0.1, 0.2) ceramics

In the present work, strontium calcium iron niobate ((Sr_1?xCa_x)Fe_0.5Nb_0.5O₃; SCFN) (x=0, 0.1, and 0.2) powders were synthesized for the first time using a molten salt technique. The pure phase perovskite obtained at a relative low calcination temperature of 800 °C was characterized using the X-ray diffraction technique (XRD). SCFN ceramics were fabricated and their properties were investigated. The XRD data of the SCFN ceramics was consistent with an orthorhombic symmetry. However, the solubility of Ca in the SCFN ceramics had an upper limit at x=0.1. All ceramics showed a large dielectric constants. The Ca doping inhibited grain growth, but produced an improvement in dielectric–temperature stability. Furthermore, the doping reduced loss tangent, especially for the x=0.1 sample. These results suggest that the SCFN ceramics prepared from molten salt synthesis exhibit a good dielectric performances, compared to many high dielectric materials that have been prepared using the conventional method.     

Synthesis and electrochemical characterization of La0.75Sr0.25Mn0.5Cr0.5−xAlxO3, for IT- and HT-SOFCs

The main emphasis of this work is to create a new perovskite material with three different compositions (La_0.75Sr_0.25Mn_0.5Cr_0.5−xAlxO₃, x = 0.1, 0.2, 0.3) applied in both Intermediate- and High-temperature Solid Oxide Fuel Cells (IT- and HT-SOFCs). Perovskite-type polycrystalline La_0.75Sr_0.25Mn_0.5Cr_0.5−xAl_xO_3−δ (x = 0.1, 0.2, 0.3) powders were synthesized and formed in a single phase structure by a dry chemistry route (standard solid-state reaction method). The effect of Al doping on physicochemical and surface properties has been discovered. The compounds were crystallized in single phase rhombohedral symmetry (R-3C Space. Group). Total conductivity of Al doping in wet 5% H₂ was higher than both dry 5% H₂ and air. The obtained results enhance the electro-catalytic performance and the material conductivity as well, which will be good for anode materials in IT- and HT-SOFCs and the optimum doping is 10%.     

Structural,dielectric and ferroelectric properties of Ba1−x(Bi0.5Na0.5)xTiO3 ceramics

Lead free Ba_1?x(Bi_0.5Na_0.5)_xTiO₃ (x=0, 0.02, 0.04, 0.06, 0.08, 0.1) ferroelectric ceramics were synthesized by conventional solid state reaction technique. Sintering was done at 1200 °C for 2 h in air atmosphere. The final products have tetragonal symmetry with decreasing c/a ratio confirmed by X-ray diffraction analysis. The grain size varies between 300 nm to 1000 nm for x=0 to 0.1. With increase in Bi_0.5Na_0.5TiO₃ [BNT] content, the room temperature permittivity decreases whereas the Curie temperature (T_c) increases and its highest value was found to be 155 °C for 10 mol% of BNT addition. The ceramics show stable and low dielectric loss characteristics. The remnant polarization (P_r) and the coercive field (E_c) increases monotonously with increase in BNT content. The highest value of 2P_r (=17 μC/cm²) and 2E_c (=22 Kv/cm) was obtained for x=10 mol% BNT addition.     

Effects of Cr substitution and oxygen reduction on elastic anomaly and ultrasonic velocity in charge-ordered Nd0.5Ca0.5Mn1−xCrxO3−δ ceramics

Charge-ordered Nd_0.5Ca_0.5Mn_1?xCr_xO_3?δ ceramics have been investigated by electrical resistivity, AC susceptibility and ultrasonic velocity measurements to elucidate the effects of Cr substitution and oxygen reduction on charge ordering (CO). Resistivity and susceptibility measurements showed that the x=0 sample exhibits insulating behavior and an anti-ferromagnetic transition at 230 K as well as a CO transition at 280 K. The substitution of Cr induces a ferromagnetic–paramagnetic and metal–insulator (MI) transition as well as gradually suppressing the CO state due to weakening of the Jahn–Teller (JT) effect. Quenching to reduce the oxygen content of the x=0.05 sample caused the MI transition temperature to shift to lower temperatures most likely due to oxygen reduction. On the other hand, both longitudinal and shear velocities at 100 K increased significantly with Cr substitution indicating improvement in elastic properties. However, quenching the x=0.05 sample slightly deceased both velocities and related elastic moduli. A step-like longitudinal velocity anomaly characterized by a slope change suggests the existence of CO state for x=0, 0.02 and 0.05 samples. The step-like anomaly shifts to lower temperatures from 266 K (x=0) to 222 K (x=0.05) with Cr substitution indicating a weakening of the CO state. Absence of the step-like anomaly for the quenched x=0.05 sample suggests suppression of the CO state due to oxygen reduction. Analysis of the step-like anomaly using the mean-field theory suggests involvement of the JT effect which transforms from dynamic to static type with decreasing temperature. Cr substitution weakened the CO state as a result of weakening the JT effect while reducing the oxygen content suppresses the CO state as a result of oxygen reduction.     

Crystal structure,microstructure and electrical properties of (1−x−y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiFeO3 ceramics near MPB prepared via the combustion technique

(1?x?y)Bi_0.5Na_0.5TiO₃–xBi_0.5K_0.5TiO₃–yBiFeO₃ (BNKFT-x/y with 0.12≤x≤0.24, 0≤y≤0.07) lead-free piezoelectric ceramics have been prepared by the combustion technique. The effects of amounts of x and y on structures and electrical properties were examined. Powders and ceramics can be well calcined and sintered at 750 °C for 2 h and 1025–1050 °C, respectively. The results indicated that the crystalline structure and microstructure changed with the increase of x and y concentrations. XRD results of BNKFT-x/0.03 and BNKFT-0.18/y ceramics with 0.12≤x≤0.24 and 0≤y≤0.07 showed the rhombohedral–tetragonal morphotropic phase boundary (MPB). The addition of y caused a promoted grain growth while the addition of x suppressed the grain growth. The highest density (ρ=5.85 g/cm³), superior dielectric properties at T_c (ε_r=7846 and tan δ=0.02), remnant polarization measured at 40 kV/cm (P_r = 20.1 μC/cm²) and piezoelectric coefficient (d₃₃=213 pC/N) were obtained for x=0.18 and y=0.03.     

High- and low-field dielectric responses and ferroelectric properties of (Bi0.5Na0.5)Zr1−xTixO3 ceramics

Bismuth sodium zirconate titanate (Bi_0.5Na_0.5)Zr_1?xTi_xO₃ with (x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) ceramics was fabricated by a conventional sintering technique at 850–1000 °C for 2 h. From X-ray diffraction study, three regions of different phases were observed in the ceramic system; i.e., orthorhombic phase region (0≤x≤0.2), mixed-phase region (0.3≤x≤0.4), and rhombohedral phase region (0.5≤x≤0.6). It was observed that the phase evolution from orthorhombic to rhombohedral symmetry resulted in a noticeable increase of the dielectric properties. The results from the high- and low-field dielectric responses indicated that the dielectric properties of both BNZ and BNZT ceramics were dominantly attributed to the reversible contribution. It was also noticed that grain size showed only partial influence on the increase of low-field dielectric constant in Ti-rich BNZT ceramic.     

The magnetization reversal and high temperature dielectric response in Y1−xHoxFe0.5Cr0.5O3

The structural, magnetic, and dielectric properties of the Y_1−xHo_xFe_0.5Cr_0.5O₃ (x=0, 0.05, 0.1, 0.3, and 0.5) compounds have been investigated. Rietveld refinement of the XRD patterns shows that the compounds possess orthorhombic perovskite structure. The dual magnetization reversal is observed in the samples with x=0.05 and 0.1, and it vanishes when x≥0.3. Ferromagnetic-like behavior with large coercive fields is observed in all Ho³⁺ doped YFe_0.5Cr_0.5O₃ samples, indicating a doping induced metamagnetic behavior. This abnormal magnetization behavior can be explained by the antiparallel magnetic coupling between the Ho³⁺ and the canted Cr³⁺/Fe³⁺ moments, as well as the Ho–O–Ho magnetic interaction. The dielectric behavior in the frequency range from 100 Hz to 10 MHz is investigated. The low doped samples (x=0, 0.05, and 0.1) exhibit relaxation-like dielectric behavior and colossal dielectric constant in a wide temperature and frequency range. The dual magnetization reversal under low magnetic field makes these materials attractive candidates for the magnetic dual sensor devices.     

Microwave dielectric properties and microstructures of Nd(Mg0.5Sn0.5−xTix)O3 ceramics

This study elucidates the microwave dielectric properties and microstructures of Nd(Mg_0.5Sn_0.5?xTi_x)O₃ ceramics with a view to their potential for microwave devices. The Nd(Mg_0.5Sn_0.5?xTi_x)O₃ ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the Nd(Mg_0.5Sn_0.4Ti_0.1)O₃ ceramics revealed no significant variation of phase with sintering temperatures. A dielectric constant (?_r) of 21.1, a quality factor (Q × f) of 50,000 GHz, and a temperature coefficient of resonant frequency (τ_f) of ?60 ppm/°C were obtained for Nd(Mg_0.5Sn_0.4Ti_0.1)O₃ ceramics that were sintered at 1550 °C for 4 h.     

Study of structural,dielectric, electric,magnetic and magnetoelectric properties of K0.5Na0.5NbO3 − Ni0.2Co0.8Fe2O4 composites

Magnetoelectric composites with general formula (x) Ni_0.2Co_0.8Fe₂O₄- (1- x) (K_0.5Na_0.5)NbO₃ (x = 0, 0.10, 0.20, 0.30, 0.40, 0.50 and 1.0) have been synthesized by solid state reaction method. X-ray diffraction pattern asserts the existence of both the constituent phases in the synthesized composites. FESEM micrographs are used to investigate the microstructure and for calculation of average grain size of the composites. Temperature dependent dielectric properties are investigated as a function of temperature and found to enhance with addition of ferrite in the composites. P-E hysteresis loops obtained for individual (K_0.5Na_0.5)NbO₃ (KNN) phase and composites indicate the ferroelectric ordering in the composites. Saturation and remnant magnetization show increasing trend with increase in NCFO concentration. FC-ZFC magnetization curves indicate charge ordering, metal-insulator transition (Verwey transition) in NCFO and composites. Impedance spectroscopy shows that bulk resistance reduces with increase in temperature, thereby indicating negative temperature coefficient of resistance (NTCR) behaviour of the composites. The magnetoelectric effect is confirmed by measuring magnetoelectric voltage coefficient, α_ME and the maximum value of α_ME is 5.389 mV/cm-Oe for 20% NCFO-80% KNN composite.     

Phase structure,piezoelectric, ferroelectric,and electric-field-induced strain properties of Nb-modified 0.8Bi0.5Na0.5TiO3−0.2Sr0.85Bi0.1TiO3 ceramics

0.8Bi_0.5Na_0.5Ti_(1-x)Nb_xO₃−0.2Sr_0.85Bi_0.1TiO₃ (BNT-SBT-xNb, x = 0.00, 0.01, 0.02, and 0.03) piezoelectric ceramics were prepared by traditional solid state reaction and the influence of Nb substitution on the phase structure, ferroelectric, piezoelectric, and electric-field-induced strain properties in BNT-SBT ceramics were studied. XRD results exhibited that Nb⁵⁺ ions could fully diffuse into BNT-SBT structure to form a solid solution when x = 0.01. P-E loops and S-E curves suggested that the ferroelectric phase transformed to ergodic relaxor state (FE-to-ER) with the increasing the amount of Nb additive, indicating the ferroelectric long-ranged order was disturbed by the excess of Nb. With increasing Nb doping, phase transition temperature from normal ferroelectric to ergodic relaxor (short for T_F-R) could be reduced from 120 °C to 40 °C. Furthermore, for sample with x = 0.01, the normalized strain d₃₃^* got a maximum value ~571 pm/V due to the phase transition from ergodic relaxor to ferroelectric (ER-to-FE) under electric field.     

New Trends and Future Opportunities in the Enzymatic Formation of C−C,C−N,and C−O bonds

Organic chemistry provides society with fundamental products we use daily. Concerns about the impact that the chemical industry has over the environment is propelling major changes in the way we manufacture chemicals. Biocatalysis offers an alternative to other synthetic approaches as it employs enzymes, Nature's catalysts, to carry out chemical transformations. Enzymes are biodegradable, come from renewable sources, operate under mild reaction conditions, and display high selectivities in the processes they catalyse. As a highly multidisciplinary field, biocatalysis benefits from advances in different areas, and developments in the fields of molecular biology, bioinformatics, and chemical engineering have accelerated the extension of the range of available transformations (E. L. Bell et al., Nat. Rev. Meth. Prim. 2021 , 1, 1–21). Recently, we surveyed advances in the expansion of the scope of biocatalysis via enzyme discovery and protein engineering (J. R. Marshall et al., Tetrahedron 2021 , 82, 131926). Herein, we focus on novel enzymes currently available to the broad synthetic community for the construction of new C−C, C−N and C−O bonds, with the purpose of providing the non-specialist with new and alternative tools for chiral and sustainable chemical synthesis.     

Experimental and theoretical study on enhanced electrical properties of nickel-substituted La0.5Sr0.5CoO3−δ ceramics

The effect of Ni substitution on the thermal behavior, crystal structure, densification, and electrical properties of La_0.5Sr_0.5Co_1–yNi_yO_3-δ (y = 0.00–0.08) (LSCN) ceramics was discussed based on experimental measurements and theoretical calculations to search for a ruthenium–free and lead–free conductive oxide for thick film resistors. Ceramics were synthesized by the solid–state reaction, and calculations were performed with first–principle density functional theory (DFT). Results showed that the replacement of Ni ion to Co ion could help decrease the densification temperature and enhance the densification level and improve the conductivity of LSCN. Theoretical calculations, including the crystal structure, bond population, total energy, and density of states (DOS), supported the experimental results well. The maximum conductivity of 3155 S/cm was achieved as y = 0.04 was sintered at 1200 °C, and the peak temperature coefficient of resistance (TCR) of 2405.7 ppm/°C occurred at y = 0.06.     

Structural,morphological and electrical properties of Ce1−xRuxO2−δ (x=0.005–0.02) solid solutions

Nanoparticles of ceria–ruthenium oxide solid solutions with composition Ce_1−xRu_xO_2−δ (x=0.005–0.02) were successfully produced by self–propagating room temperature synthesis using reaction between metal nitrates and sodium hydroxide. These compositions were characterized by X–ray powder diffraction (XRD), Raman spectroscopy, specific surface area, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X–ray spectroscopy (EDX). The experimental measurements were complemented by calculations based on the ion–packing model. XRD analysis revealed the presence of single–phase solid solutions with CeO₂ fluorite structure (regardless of dopants concentration) and Raman spectroscopy confirmed the presence of the RuO₂ phase. Electrochemical impedance spectroscopy (EIS) measurements of sintered samples at different temperatures showed that the small ionic radius dopant reduces oxygen vacancies mobility that is responsible for the conductivity of these ceramics.     

Phase-microstructure evolution and microwave dielectric characteristic of (1−x)(Sr0.5Ce0.5)TiO3+δ−xNdAlO3 solid solution

A perovskite solid solution (1−x)(Sr_0.5Ce_0.5)TiO_3+δ−xNdAlO₃, x = 0.1 to 0.4 was prepared by conventional solid state method. X-ray diffraction spectra revealed a single phase with tetragonal structure, indicating that doping of NdAlO₃ significantly stabilized the perovskite-like structure. The addition of NdAlO₃ facilitated the formation of large plate-like grains with porous microstructure. The dielectric constant (ε_r) decreased with increasing x because of the small ionic polarizability of NdAlO₃. The Q × f value was strongly dependent on the microstructure of these ceramics. The temperature coefficient of resonant frequency (τ_f) gradually shifted to near zero with a rise of x, which resulted from the decrease in tolerance factor (t). The solid solution with x = 0.4 sintered at 1550 °C for 4 h showed a good combination of dielectric properties: ε_r = 72, Q × f = 12052 GHz and τ_f = +5 pmm/°C.     

Structural,electrical and magnetic properties of Co0.5Zn0.5AlxFe2−xO4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) prepared via sol–gel route

Nanoparticles of Co_0.5Zn_0.5Al_xFe_2?xO₄ (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized by sol–gel method and the influence of Al³⁺ doping on the properties of Co_0.5Zn_0.5Fe₂O₄ was studied. X-ray diffraction studies revealed the formation of single phase spinel type cubical structure having space group Fd-3m. A decreasing trend of the lattice parameter was observed with increasing Al³⁺ concentration due to the smaller ionic radii of Al³⁺ ion as compared to Fe³⁺ ion. TEM was used to characterize the microstructure of the samples and particle size determination, which exhibited the formation of spherical nanoparticles. The particle size was found to be increases up to ～45 nm after annealing the sample at 1000 °C. Electrical resistivity was found to increase with Al³⁺ doping, attributed to the decrease in the number of Fe²⁺–Fe³⁺ hopping. The activation energy decreased with increasing Al³⁺ ion concentration, indicating the blocking of conduction mechanism between Fe³⁺–Fe²⁺ ions. The value of saturation magnetization decreased, when Fe³⁺ ions were doped with Al³⁺ ions in Co_0.5Zn_0.5Fe₂O₄; however, the coercivity values increased with increasing Al³⁺ ion content.     

Structural,magnetic and magnetocaloric study of La0.7−xEuxSr0.3MnO3 (x=0.1, 0.2 and 0.3) manganites

This paper reports the structural, magnetic and magnetocaloric properties of La_0.7−xEu_xSr_0.3MnO₃ (x=0.1, 0.2 and 0.3) polycrystalline manganites elaborated using the solid-state reaction at high temperatures. The X-ray powder diffraction shows that all the prepared compounds are single phase. La_0.6Eu_0.1Sr_0.3MnO₃ is crystallized in the rhombohedral symmetry, whereas a structural transition towards orthorhombic system is observed for x≥0.2. Eu doping was found to induce a decrease of the Curie temperature T_C from 343 K (x=0.1) to 272 K (x=0.3). All compounds undergo a large magnetocaloric effect and have consequently potential applications in magnetic refrigeration domain around room temperature.     

Fatty acids,the immune response,and autoimmunity: A question of n−6 essentiality and the balance between n−6 and n−3

The essentiality of n−6 polyunsaturated fatty acids (PUFA) is described in relation to a thymus/thymocyte accretion of arachidonic acid (20∶4n−6, AA) in early development, and the high requirement of lymphoid and other cells of the immune system for AA and linoleic acid (18∶2n−6, LA) for membrane phospholipids. Low n−6 PUFA intakes enhance whereas high intakes decrease certain immune functions. Evidence from in vitro and in vivo studies for a role of AA metabolites in immune cell development and functions shows that they can limit or regulate cellular immune reactions and can induce deviation toward a T helper (Th)2-like immune response. In contrast to the effects of the oxidative metabolites of AA, the longer-chain n−6 PUFA produced by γ-linolenic acid (18∶3n−6, GLA) feeding decreases the Th2 cytokine and immunoglobulin (Ig)G1 antibody response. The n−6 PUFA, GLA, dihomo-γ-linolenic acid (20∶3n−6, DHLA) and AA, and certain oxidative metabolites of AA can also induce T-regulatory cell activity, e.g., transforming growth factor (IGF)-β-producing T cells; GLA feeding studies also demonstrate reduced proinflammatory interleukin (IL)-1 and tumor necrosis factor (TNF)-α production. Low intakes of long-chain n−3 fatty acids (fish oils) enhance certain immune functions, whereas high intakes are inhibitory on a wide range of functions, e.g., antigen presentation, adhesion molecule expression, Th1 and th2 responses, proinflammatory cytokine and eicosanoid production, and they induce lymphocyte apoptosis. Vitamin E has a demonstrable critical role in long-chain n−3 PUFA interactions with immune functions, often reversing the effects of fish oil. The effect of dietary fatty acids on animal autoimmune disease models depends on both the autoimmune model and the amount and type of fatty acids fed. Diets low in fat, essential fatty acid deficient (EFAD), or high in long-chain n−3 PUFA from fish oils increase survival and reduce disease severity in spontaneous autoantibody-mediated disease, whereas high-fat LA-rich diets increase disease severity. In experimentally induced T cell-mediated autoimmune disease, EFAD diets or diets supplemented with long-chain n−3 PUFA augment disease, whereas n−6 PUFA prevent or reduce the severity. In contrast, in both T cell- and antibody-mediated autoimmune disease, the desaturated/elongated metabolites of LA are protective. PUFA of both the n−6 and n−3 families are clinically useful in human autoimmune-inflammatory disorders, but the precise mechanisms by which these fatty acids exert their clinical effects are not well understood. Finally, the view that all n−6 PUFA are proinflammatory requires revision, in part, and their essential regulatory and developmental role in the immune system warrants appreciation.     

Phase structure,ferroelectric properties,and electric field-induced large strain in lead-free 0.99[(1−x)(Bi0.5Na0.5)TiO3-x(Bi0.5K0.5)TiO3]–0.01Ta piezoelectric ceramics

Lead-free 0.99[(1−x)(Bi_0.5Na_0.5)TiO₃-x(Bi_0.5K_0.5)TiO₃]–0.01Ta piezoelectric ceramics were prepared by a conventional solid-state reaction process. The ferroelectric properties, and strain behaviors were characterized. Increase of the (Bi_0.5K_0.5)TiO₃ content induces a phase transition from coexistence of ferroelectric tetragonal and rhombohedral to a relaxor pseudocubic phase. Accordingly, the ferroelectric order is disrupted significantly with the increase of (Bi_0.5K_0.5)TiO₃ content and the destabilization of the ferroelectric order is accompanied by an enhancement of the unipolar strain, which peaks at a value of 0.35% (corresponding to a large signal d₃₃ of 438 pm/V) in samples with 20 mol% (Bi_0.5K_0.5)TiO₃ content. Temperature dependent measurements of both polarization and strain from room temperature to 120 °C suggested that the origin of the large strain is due to a reversible field-induced nonpolar pseudocubic-to-polar ferroelectric phase transformation.     

Physical–chemical property and activity evaluation of LaB0.5Co0.5O3 (B = Cr,Mn, Cu) and LaMnxCo1−xO3 (x = 0.1, 0.25, 0.5) nano perovskites in VOC combustion

The correlation between physical–chemical properties and activities of LaB_0.5Co_0.5O₃ (B = Cr, Mn, Cu) nano perovskites was studied in combustion of toluene. LaMn_0.5Co_0.5O₃ showed the highest activity among LaB_0.5Co_0.5O₃ catalysts and further optimization study was focused on LaMn_xCo_1?xO₃ (x = 0.1, 0.25, 0.5). The activity and reducibility of catalysts improved due to partial substitution of Co³⁺ by B cation. No direct relationship was between surface area and catalyst activity. T_50% of 2-propanol over LaMn_0.25Co_0.75O₃, LaMn_0.5Co_0.5O₃, LaMn_0.1Co_0.9O₃ and LaCoO₃ was 168, 200, 220 and 229 °C, respectively. LaMn_0.25Co_0.75O₃ was the optimum catalyst and showed robust stability in combustion of toluene and 2-propanol.