LaFeO3 Particles Research Articles

Composite polymer electrolyte facilitated by enhanced amorphousity and Li+ conduction using LaFeO3-embedded PVDF-HFP for solid-state lithium metal battery

Composite polymer electrolytes (CPEs) are a promising alternative to flammable conventional liquid electrolytes for high-safety lithium-ion batteries. Establishing low-cost filler that enhances the amorphous nature of polymer in the CPEs and exhibits efficient Lewis acid-base interaction between fillers and anions of lithium salt, leading to improved dissociation of salts for enhanced conduction, is indispensable. In this work, for the first time, we construct a solid composite polymer electrolyte of poly(vinylidene fluoride hexafluoropropylene) embedded LaFeO3 (LFO) particles prepared by solution casting and electrospinning methods and study their performances. The 5 wt% LFO filler embedded CPE made by means of solution casting and electrospinning methods exhibited the highest ionic conductivity of 5.9 × 10-4 and 1.49 × 10-3 S cm−1 at room temperature and electrochemical stability window up to 4.6 and 4.45 V, respectively. Further, as-assembled solid-state lithium-ion batteries using electrospun CPE showed an initial discharge capacity of 166 mAh/g at 0.1C-rate and solution-casted CPE showed excellent cycling stability with 98.6 % capacity retention at 0.3C-rate even at 50th cycle. Such excellent performance originated from the introduction of the LFO particles as filler into the polymer matrix to enhance the ionic conductivity, mechanical strength and lithium metal compatibility of the resulting CPEs.

The roles of oxygen vacancies in LaFeO3 photocathodes in photoelectrochemical water splitting

In this study, we prepared oxygen vacancies (VO) modified LaFeO3 particles using a simple molten salt method by tuning the cation (La3+) deficiency. The existence of VO was confirmed by studying its crystal structure and surface chemical state. By testing the photoelectrochemical (PEC) activity of the Vo modified La1-xFeO3-σ photocathodes in a 0.1 M NaOH electrolyte under visible light, the results demonstrate that the as-prepared La0.9FeO3-σ shows good stability and superior IPCE, which is 3.27 times that of the pristine LaFeO3. Even through VO modification is an effective strategy for regulating the PEC performance of a semiconductor, the charge carrier density in semiconductor is not directly proportional to the amount of VO, as excessive VO may lead to deterioration of the electrochemical reaction due to interfacial charge recombination. Introducing suitable amount of VO into LaFeO3 can improve the light absorption, boost charge carrier transfer and separation efficiency, narrow the bandgap, and enhance the electrocatalytic reaction dynamics at the semiconductor surface.

Ultrasound-assisted preparation of LaFeO3/polystyrene for efficient photo-Fenton degradation of ciprofloxacin hydrochloride

LaFeO3/polystyrene (LFO/PS) was successfully prepared by depositing perovskite-type LaFeO3 particles on polystyrene using ultrasound-assisted sol-gel and hydrothermal methods. The structure and properties of LFO/PS were also investigated using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), photoluminescence spectra (PL) and other characterization methods. The results showed that the introduction of ultrasound increased the adsorbed oxygen and oxygen vacancy content of LaFeO3. The deposition of LaFeO3 on PS improved the specific surface area of LaFeO3 and solved the problems of easy agglomeration and difficult separation of powdered LaFeO3. The effects of H2O2 concentration, catalyst dosage, solution concentration, pH and inorganic anions on the removal efficiency of ciprofloxacin hydrochloride were also investigated. The removal efficiency of ciprofloxacin hydrochloride by the LaFeO3/polystyrene photo-Fenton system (98.38%) was much higher than that by pure LFO (sonicated, 54.07%) and LFO/PS (unsonicated, 79.88%) photo-Fenton systems under CCIP = 10 mg/L, CH2O2 = 5 mmol/L, dosage = 1.0 g/L, and pH = 9.00. Furthermore, the removal efficiency of total organic carbon (TOC) reached 76.44%. Based on the identification of intermediates by liquid chromatography-mass spectrometry and density functional theory calculations, the main degradation pathways of ciprofloxacin hydrochloride were proposed. This study explores the influence of various factors on oxygen-rich vacancy perovskite/polystyrene in environmental remediation and proposes the advantages of the introduction of ultrasound in catalyst preparation process.

Facile fabrication of LaFeO3/zeolite composite for degradation of tetracycline with enhanced photo‐Fenton catalytic activity under visible light

AbstractLaFeO3/zeolite (LFO‐Z) composite has been successfully synthesized via impregnation‐calcination method for the photo‐Fenton degradation of Tetracycline (TC). The incorporation of LaFeO3 particles on zeolite support contributes to the enhancement in photo‐Fenton catalytic activity of LFO‐Z photocatalyst by increasing the contact area between the material and TC molecules. The LFO‐Z photocatalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), N2 adsorption‐desorption, and optical absorption spectra. Different operational parameters such as catalyst dosage, H2O2 concentration, pH was investigated in the photo‐Fenton catalytic degradation of TC. 76.4 % of TC was degraded after 150 min exposure to visible light under the conditions of 1 g L‐1 LFO‐Z, 10 mg L‐1 TC, 10 mM H2O2 and pH of 6. The LFO‐Z composite shows a high stability and reusability, suggesting its potential use as a photocatalyst for pharmaceutical degradation via the photo‐Fenton process.

In-situ template formation method to synthesize hierarchically porous carbon for electrocatalytic reduction of 4-nitrophenol

An in-situ template formation method is reported for the synthesis of hierarchically porous carbon (PC), with La and Fe nitrates as template precursors and citric acid as carbon precursor. During the carbonization, La and Fe oxides, originated from the metal nitrates, move together and react with each other to form LaFeO3 particles, serving as hard template of the PC. Thus, three types of pores are generated in the PC through (1) the release of gases, (2) the movement of La and Fe oxides and (3) the etching of LaFeO3 particles. TPD-MS and Zeta potential results indicate that the PC contains mainly surface acidic carboxylic groups. Catalytic tests for electroreduction of 4-nitrophenol show that the PC-c is active for the reaction with reduction potential of −0.445 V and peak current of 108.8 μA, which is 3 times higher than that of the PC-g, due to its larger surface area and especially, the richer surface functional groups, which are the active sites of the reaction.

Degradation of organic contaminants in marine sediments by peroxymonosulfate over LaFeO3 nanoparticles supported on water caltrop shell-derived biochar and the associated microbial community responses

Sediment is an important final repository of persistent organic pollutants such as polycyclic aromatic hydrocarbons (PAHs). Herein, a novel catalyst of LaFeO3 nanoparticles supported on biochar was synthesized from water caltrop shell by chemical precipitation. The composite (LFBC) was used as peroxymonosulfate (PMS) activator to oxidize PAHs in real marine sediments. Systematic surface characterization confirmed the immobilization of well crystalline nano LaFeO3 particles onto the biochar surface. Under optimal conditions, i.e., [PMS] = 3 × 10-4 M, [LFBC] = 0.75 g/L, pH 6.0, and seawater, the total PAH degradation efficiency was 90%, while that of 2-, 3-, 4-, 5-, and 6-ring PAHs was 52%, 61%, 66%, 56%, and 29%, respectively, in 24 h. The Langmuir-Hinshelwood equation better predicted the PAHs degradation kinetics over LFBC by PMS. Interactions between surface oxygen species at LaFeO3 defective sites and the graphitized biochar network facilitated the PAHs degradation. Furthermore, changes in the bacterial community during the LFBC/PMS treatment were highlighted to assess the sustainable development of the sediment ecosystem. The LFBC/PMS process enhanced the biological richness and diversity of sediment eco-systems. The major phylum was Proteobacteria initially, while Hyphomonas was the genera after LFBC/PMS treatment of the sediment.

Enhanced electrochemical performance of lanthanum ferrite decorated reduced graphene oxide nanocomposite electrodes prepared by in situ microwave irradiation for energy storage applications

SummaryLanthanum ferrite decorated reduced graphene oxide (LaFeO3/rGO) nanocomposite is prepared by in‐situ microwave irradiation method. The X‐ray diffraction study reveals the single phase orthorhombic structure of LaFeO3 nanoparticles and LaFeO3/rGO nanocomposites. The FTIR study reveals various vibrational modes and the characteristic D and G bands of the Raman spectrum confirms the formation of reduced graphene oxide. The SEM and HR‐TEM images demonstrate that spherical LaFeO3 particles are decorated on 2D graphene sheets. From the HR‐TEM study, the average particle size of LaFeO3 is estimated to be 23 nm. The synergistic effect of 3D LaFeO3 nanoparticles and 2D graphene layers offers more active sites to achieve the enhanced electrochemical performance. The specific capacitance of LaFeO3/rGO composites is measured to be 170 Fg−1 at 10 mV s−1. The composite electrode has admirable cyclic stability, better Columbic efficiency and improved capacitance retention with great potential for supercapacitor applications.

Deposition of perovskite-type LaFeO3 particles on spherical commercial polystyrene resin: A new platform for enhanced photo-Fenton-catalyzed degradation and simultaneous wastewater purification

Abstract The application of nanosized photocatalytic materials in powder form bring some drawbacks like agglomeration and difficulty in separation in scale up processes. In this study, commercial polystyrene based resin was offered as a new platform for the deposition of catalyst nanoparticles. For this purpose, perovskite LaFeO3 nanoparticles were deposited on Diaion TM HP21 resin via a facile hydrothermal process and the heterostructured catalyst exhibited enhanced ultraviolet–visible light absorption efficiency, photocatalytic, Fenton and photo-Fenton catalytic activities towards tetracycline antibiotic. The effect of solution pH, stability and the degradation intermediates of tetracycline as well as environmental application in different water media under sunlight irradiation were also explored. Furthermore, the catalytic degradation mechanism was examined with reactive radical scavenger tests. Apart from tetracycline molecule, the photo-Fenton catalytic activities of the heterostructured catalyst with respect to different dye and antibiotic components were also investigated to establish the relationship between adsorption and photocatalysis. Exploring the possible utilization of the newly designed commercial resin not only solving the environmental issue but also highlighting its further usage with the concept of “photocatalysis”.

Effect of AgO loading on flame-made LaFeO3p-type semiconductor nanoparticles to acetylene sensing

In this work, unloaded and Ag-loaded LaFeO3 gas sensors produced using flame spray pyrolysis (FSP) for the first time were investigated for acetylene gas-sensing applications. From the structural analyses using X-ray diffraction, electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy that the formation of AgO nanoclusters on spherical LaFeO3 particles was identified. From gas-sensing measurements, the unloaded LaFeO3 sensor displayed high sensitivity and selectivity to low concentrations (< 500 ppm) of acetylene. The 0.1 wt% Ag-loaded LaFeO3 sensor gave the highest sensor signal (60) towards 100 ppm acetylene, which is almost 12 times higher than the pure material at an optimal working temperature of 200 °C. In addition, it exhibited low cross sensitivity to hydrogen, carbon monoxide, ethylene, methane and carbon dioxide. Higher Ag loading (1 wt%) resulted in low sensitivity and no selectivity to acetylene. Loading with Ag at the low content (0.1 wt%) also lowered the humidity dependence of the sensor response. Through a detailed analysis, the enhanced acetylene-sensing performance of Ag-loaded LaFeO3 could be attributed to a Fermi-level control mechanism. It was found that the FSP-made LaFeO3-based gas sensors are better than other materials for sensing low acetylene concentrations in practical applications such as the dissolved gas analysis of transformer oil.

Construction of stable perovskite-type LaFeO3 particles on polymeric resin with boosted photocatalytic Fenton-like decaffeination under solar irradiation

In this work, LaFeO3 perovskite particles were successfully immobilized on the commercial polymeric resin (Amberlite XAD-4) to yield a novel and applicable photocatalyst. The prepared catalysts were systematically characterized by XRD, XPS, FTIR, SEM, TEM-EDX, UV-DRS, PL and TGA analyses. It is demonstrated that LaFeO3 particles (LFO) with well crystallinity were immobilized onto the surface of resin, leading to the formation of composite LFO/XAD4 catalyst. The signals of La 3d, Fe 2p and O 1s on the composite were further confirmed by the XPS spectroscopy. The photocatalytic, Fenton and photo-Fenton performances of the samples were investigated by degrading caffeine under visible light illumination. Such an immobilization of the LaFeO3 particles onto the resin significantly altered the photocatalytic and photo-Fenton degradation of caffeine; the photo-Fenton degradation rate in the presence of the bare LaFeO3 (41.5%) enhanced to 78.5% after immobilization suggesting that the synergetic effect of adsorption and photocatalysis played a major role in the decaffeination process. Moreover, the increasing LaFeO3 ratio to a certain level over the resin surface greatly improved the degradation which could be resulted in more absorption of light radiation and enhanced transfer of the photo-induced electrons. The photo-Fenton catalytic mechanism under sun light illumination was also discussed in terms of solution pH, H2O2 concentration, co-existing anions and scavengers. In addition, reusability tests revealed that the immobilization also eases the separation and stability of the catalyst which can be effectively used until sixth cycle. The degradation pathways of photo-Fenton degradation of CAF were proposed. This work gives an insight into the usage of polymeric resins as potential supporting materials in the photocatalysis field.

Facile synthesis of g-C3N4/ LaMO3 (M: Co, Mn, Fe) composites for enhanced visible-light-driven photocatalytic water splitting

C3N4 was used as a base semiconductor for the formation of composites with LaMO3 (M: Co, Mn, Fe) perovskite powders prepared by sol-gel (SG) and solid-state (SS) through an easy impregnation method. The optical analysis showed a redshift displacement in the case of C3N4/LaMnO3 and C3N4/LaCoO3 composites due to perovskite particles act as electron traps. By photoluminescence, we elucidate that LaFeO3 generates intermediate states inside the structure of C3N4 indicating an intimate intermixing, which is also corroborated by electrochemical characterizations. The activity of the composites towards the hydrogen evolution reaction was tested under simulated solar irradiation without sacrificial agent neither noble metals. Incorporation of 2% of perovskite over C3N4 showed the best efficiencies. C3N4/2%LaFeO3 SG and C3N4/2%LaFeO3 SS showed the highest activities (140 μmol h−1 g−1 and 40 μmol h−1 g−1 respectively). These results are attributed to the better coupling between C3N4 and LaFeO3 and the formation of a type II heterostructure. Meanwhile, the activity of C3N4/LaMnO3 and C3N4/LaCoO3 composites exhibited lower performance compared with composites prepared with LaFeO3 particles, related to the creation of a type I heterostructure where the flow of charges is not efficient, limiting the photocatalytic performance.

A promising Ag2CrO4/LaFeO3 heterojunction photocatalyst applied to photo-Fenton degradation of RhB

ABSTRACTAg2CrO4 nanoparticles (10–35 nm) were assembled onto LaFeO3 nanoparticles (20–60 nm) via a facile chemical precipitation method to form novel Ag2CrO4–LaFeO3 heterojunction composite photocatalysts. The prepared Ag2CrO4–LaFeO3 composites were characterized by XRD, SEM, TEM, XPS, BET, UV-vis DRS, PL spectroscopy and EIS and photocurrent response. The TEM result clearly shows that Ag2CrO4 particles are decorated onto LaFeO3 particles to form Ag2CrO4–LaFeO3 heterojunction. Compared to bare LaFeO3, the 10%Ag2CrO4-LaFeO3 composite exhibits a slightly increased BET specific surface area, increased photocurrent density, decreased charge-transfer resistance and decreased PL emission peaks. Using simulated sunlight as the light source and in the presence of H2O2, the photo-Fenton performance of the composite photocatalysts toward the degradation of RhB was investigated, revealing that they manifest significantly enhanced photo-Fenton degradation of RhB when compared with bare LaFeO3 and Ag2CrO4. Among the composite photocatalysts, 10%Ag2CrO4–LaFeO3 exhibits the highest photo-Fenton activity, which is about 3.1 and 2.5 times higher than that of bare LaFeO3 and Ag2CrO4, respectively. This is attributed to the fact that the composite photocatalysts have highly efficient separation of photogenerated electron–hole pairs due to the formation of Ag2CrO4–LaFeO3 heterojunctions. Active species trapping experiments and ·OH detection experiments were carried out, from which it is concluded that ·OH radicals are the dominant reactive species causing the dye degradation. A synergistic mechanism was proposed to elucidate the enhanced photo-Fenton activity of Ag2CrO4–LaFeO3 heterojunction composites.

Dielectric and ferroelectric properties of LaFeO3 particles derived from metal organic frameworks precursor

As one of the few single-phase multiferroic materials with both antiferromagnetic and ferroelectric properties, LaFeO3 has attracted much attention, especially film and ceramic. In this work, LaFeO3 particles were prepared by thermal decomposition of Metal Organic Frameworks (MOFs) precursor La[Fe(CN)6]·5H2O, and the dielectric and ferroelectric properties of particles were studied for the first time. The effect of annealing temperature and time on the dielectric and ferroelectric performance were investigated in detail. The results indicate that the LaFeO3 particles annealed at 600 °C for 5 h achieve dielectric constant of 201, remnant polarization 2Pr of 0.064 μC/cm2 with coercive electric field 2Ec of 39.16 kV/cm, higher than those of other annealing time. In addition, the LaFeO3 particles annealed at 700 °C for 3 h exhibit dielectric constant of 178 and remnant polarization 2Pr of 0.072 μC/cm2 which are higher compared with other annealing temperatures. Our results provide useful information to study LaFeO3 particles.

Enhanced electrochemical properties of LaFeO3 with Ni modification for MH–Ni batteries

In this work, we synthesized LaFeO3–xwt%Ni (x = 0, 5, 10, 15) composites via a solid-state reaction method by adding Ni to the reactants, La2O3 and Fe2O3. Field-emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) results revealed that Ni powders evenly dispersed among the LaFeO3 particles and apparently reduced their aggregation, which imparted the composites with a loose structure. Moreover, the Ni formed a conductive network, thus improving the conductivity of the composites. The maximum discharge capacity of the LaFeO3 electrodes remarkably increased from 266.8 mAh·g–1 (x = 0) to 339.7 mAh·g–1 (x = 10). In particular, the high-rate dischargeability of the LaFeO3–10wt%Ni electrode at a discharge current density of 1500 mA·g−1 reached 54.6%, which was approximately 1.5 times higher than that of the pure LaFeO3. Such a Ni-modified loose structure not only increased the charge transfer rate on the surface of the LaFeO3 particles but also enhanced the hydrogen diffusion rate in the bulk LaFeO3.

Enhanced photocatalytic performance and mechanism of Ag-decorated LaFeO3 nanoparticles

Spherical LaFeO3 nanoparticles with an average size of 35 nm were synthesized by a polyacrylamide gel route. Ag nanoparticles of 8–18 nm in size were decorated onto LaFeO3 particle surface by a chemical reduction method to yield Ag–LaFeO3 composites. The samples were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy, and photoluminescence spectroscopy. It is found that LaFeO3 particles have two bandgap energies of 2.59 and 2.24 eV, which undergo almost no change when decorated with Ag nanoparticles. photoluminescence spectra demonstrate that the decoration of LaFeO3 particles with Ag nanoparticles leads to a decreased recombination rate of photogenerated electrons and holes. The photocatalytic activity of the samples was evaluated by degrading Rhodamine B under simulated-sunlight irradiation. Compared to bare LaFeO3 particles, Ag–LaFeO3 composites exhibit an obviously enhanced photocatalytic activity. The formed •OH was examined by photoluminescence spectroscopy using terephthalic acid as the •OH scavenger, revealing an enhanced yield on the irradiated Ag–LaFeO3 composites. To clarify the role of active species in the photocatalysis, the effect of ammonium oxalate (h+ scavenger), ethanol (•OH scavenger), benzoquinone (•O2 − scavenger), and N2 on the Rhodamine B degradation as well as the •OH yield was investigated. Based on the experimental results, •OH and •O2 − are suggested to be the main active species causing the dye degradation.

Development of enhanced surface area LaFeO3 perovskites using amino acids as templating agents

In this article LaFeO3 perovskites of enhanced specific surface area (ssa) have been developed through a soft templating path which involves amino acids as capping agents of primary particles, in order to suppress aggregating effects, and polymer P123 as a surface enhancing agent. The treatment of the primary LaFeO3 particles took place using the amino acids β-alanine, serine, tyrosine and threonine and the final surface area increased from 18 up to 42⿿59m2/g, depending on the amino acid. The obtained material showed also a remarkable red shift band gap. The main factor affecting the development of ssa seems to be the interactions between the solid particles and the amphiphilic molecules, which in turn are controlled by the Accessible surface area and the Hydropathy Index of side chain as well as the solubility of amino acid.

Formaldehyde-sensing properties of LaFeO3 particles synthesized by citrate sol–gel method

LaFeO3 (LFO) particles were synthesized by citrate sol–gel method and characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and specific surface and pore size analysis instrument. To investigate the formaldehyde (HCHO)-sensing properties, the side-heating gas sensor based on LFO particles was fabricated. The LFO particle-based gas sensor presented high response and good selectivity to HCHO at an operating temperature of 100 °C. At the range of 1–50 ppm HCHO, the LFO particle-based gas sensor exhibits a nearly linear response, and the linear correlation coefficient is 0.99. The response time and recovery time are about 33 and 27 s, respectively. The results indicate that LFO particles synthesized by citrate sol–gel method have potential applications for fabricating high-performance and low power consumption HCHO gas sensor.

Study on the high-temperature electrochemical performance of perovskite-type oxide LaFeO3 with carbon modification

To further improve the high-temperature electrochemical performance of perovskite-type oxides, the LaFeO3 carbon-coated composites used as the negative materials for MH-Ni batteries were obtained using the polyaniline (PANI) pyrolysis method. Transmission electron microscopy (TEM) results revealed that LaFeO3 particles were evenly coated with carbon layers, forming a core–shell structure. The carbon layers could enhance the conductivity and electrocatalytic activity, speeding up hydrogen protons transferring from electrolyte to electrode interface. Furthermore, the carbon coatings hindered the LaFeO3 particles from aggregating into stacks and reduced the corrosion of the LaFeO3 electrodes. At an elevated temperature (60 °C), owing to the carbon coatings, the maximum discharge capacity of the LaFeO3 electrodes remarkably increased from 211 mAh g−1 to 358 mAh g−1, and charge retention (CR) increased from 85.4% to 94.6%. Also, the high rate dischargeability at a discharge current density of 1500 mA g−1 (HRD1500) increased from 21.0% to 37.6%, and the capacity retention rate after 100 cycles (S100) increased from 63.0% to 70.9%.

Photoelectrochemical Properties of LaFeO3 Nanoparticles

AbstractThe photoelectrochemical properties of LaFeO3 nanoparticles are discussed for the first time. Highly phase‐pure LaFeO3 particles prepared by a novel ionic‐liquid‐based method are characterized by a (60±14) nm mean size and a band gap of (2.56±0.07) eV. Thin films deposited by screen printing exhibit photocurrent responses associated with hydrogen generation at potential up to 1 V more positive than the formal hydrogen potential. Analysis of the photocurrent responses as a function of photon flux and potential bias suggest that the hole‐collection efficiency at the back contact is in competition with interfacial water oxidation.

Sol-gel preparation and magnetic properties of nanocrystalline lanthanum ferrite

LaFeO3 nanoparticles (30–40 nm) have been prepared via the sol-gel method using polyvinyl alcohol as a stabilizer. Addition of polyvinyl alcohol results in the formation of smaller LaFeO3 particles and decreases the temperature of transition into the single-phase product as compared with the samples prepared via precipitation with aqueous ammonia. Residual magnetization, magnetization at saturation, and coercive force of LaFeO3 nanoparticles are monotonous decreasing functions of the nanopowder annealing temperature.