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The electrochemical CO2 reduction reaction (CER) to methane (CH4) has received great attention. Here, we proposed an efficient method to facilitate the conversion of CO2-to-CH4 by creating a two-phase interface over urea-modified La2CuO4 catalyst. The most optimized one exhibits the highest selectivity (22%) for CH4 and the best activity (14 mA cm−2) and stability (5 h) at the potential of −1 V vs. reversible hydrogen electrode. The enhanced CER performance can be attributed to the establishment of interfacial effect within the two-phase, which facilitates the reduction of Cu2+ and promotes the active sites concentration.

The structural transformations, oxygen releasing and side reactions with electrolytes on the surface are considered as the main causes of the performance degradation of Li-rich layered oxides (LROs) cathodes in Li-ion batteries. Thus, stabilizing the surfaces of LROs is the key to realize their practical application in high energy density Li-ion batteries. Surface coating is regarded as one of the most effective strategies for high voltage cathodes. The ideal coating materials should prevent cathodes from electrolyte corrosion and possess both electronic and Li-ionic conductivities simultaneously. However, commonly reported coating materials are unable to balance these functions well. Herein, a new type of coating material, La2CuO4 was introduced to mitigate the surface issues of LROs for the first time, due to its superb electronic conductivity (26–35 mS⋅cm−1) and lithium-ionic diffusion coefficient (10−12–10−13 cm2⋅s−1). After coating with the La2CuO4, the capacity retention of Li1.2Ni0.54Co0.13Mn0.13O2 cathode was increased to 85.9% (compared to 79.3% of uncoated cathode) after 150 cycles in the voltage range of 2.0–4.8 V. In addition, only negligible degradations on the deliverable capacity and rate capability were observed. [ABSTRACT FROM AUTHOR]

Thermoelectric properties of polycrystalline La2CuO4 with (x = 0.0, 0.02, 0.05, 0.10, 0.15, 0.20) have been examined. For this, the samples have been synthesised via solid‐state reaction (SSR) technique. For microstructural analysis of investigated pellets, X‐ray diffraction and scanning electron microscopy have been performed. The electrical resistivity and Seebeck coefficient of the investigated samples have been measured with the help of an in‐house fabricated setup, capable to measure the resistivity and thermopower between 100 and 400 K with ±3% experimental uncertainty. The electrical resistivity reveals a semiconducting nature for pristine pellets. However, a transition to metallic nature of electrical resistivity is observed for Sr doping concentration ≥ 0.02. The Seebeck coefficient (S) of investigated pellets is found to be positive, which indicates holes type conduction. Apart from that, a gradual decrease in the Seebeck coefficient has also been noticed as Sr dose increases. Again, the sample with Sr concentration x = 0.02 is found to be the best with a maximum power factor value (6.947 μW/cm K2) at 165 K, which is a positive sign for future applicability of LSCO‐based oxide materials for energy harvesting applications below room temperature. [ABSTRACT FROM AUTHOR]

• Zn doping affects the densification, grain size, and resistivity of La 2 CuO 4 ceramics. • The Jahn-Teller distortion in the CuO 6 octahedron is mitigated after Zn doping. • Zn doping increases the Metal-insulator transition temperature (T MI) of La 2 CuO 4. The structure and electrical properties of layered perovskites La 2 Cu 1- x Zn x O 4 have been investigated. The resistivity of these samples has been measured in the temperature range of 90–300 K. The Zn2+doping induces a shift of the metal–insulator transition temperature towards the high-temperature region. The d9 electronic configuration of Cu2+ in La 2 CuO 4 leads to an uneven distribution of electron clouds, inducing axial stretching of the surrounding oxygen octahedra and resulting in Jahn-Teller distortion. After Zn2+ doping, the charge compensation induces a partial transformation of Cu2+ to Cu+. As a result, the positions occupied by Cu2+ are replaced by Zn2+ and Cu+ with perfectly symmetric electron clouds in the 3d10 outer electronic configuration, thus suppressing the Jahn-Teller effect. This shifts the phonon scattering, which is responsible for the emergence of the metal's conductive properties, to higher temperatures. [ABSTRACT FROM AUTHOR]

Compared with the traditional thermoelectric semiconductors, the research progress of thermoelectric oxides with high‐temperature thermal stability is far behind. In this work, a layered copper oxide La2CuO4 was synthesized by combining the high‐energy ball milling, solid state reaction and spark plasma sintering. By introducing metal elements (Ba, Sr, Pb) at La site, the increased carrier concentration with optimized electrical transport properties were achieved in La2CuO4‐based thermoelectric oxides. Results showed that Ba has the best doping effect among the three dopants, with an optimal carrier concentration of ∼1020 cm−3. Furthermore, the figure of merit (ZT) value was enhanced over the entire temperature range with a maximum ZTave of ∼0.03 at 300–923 K, which is nearly two orders of magnitude higher than that of printine La2CuO4. Our research has successfully developed the thermoelectric properties of La2CuO4‐based oxide, which has the great potential to be a reliable candidate as the thermocouple for high‐temperature detection in the key parts of aircrafts. [ABSTRACT FROM AUTHOR]

Compared with the traditional thermoelectric semiconductors, the research progress of thermoelectric oxides with high‐temperature thermal stability is far behind. In this work, a layered copper oxide La2CuO4 was synthesized by combining the high‐energy ball milling, solid state reaction and spark plasma sintering. By introducing metal elements (Ba, Sr, Pb) at La site, the increased carrier concentration with optimized electrical transport properties were achieved in La2CuO4‐based thermoelectric oxides. Results showed that Ba has the best doping effect among the three dopants, with an optimal carrier concentration of ∼1020 cm−3. Furthermore, the figure of merit (ZT) value was enhanced over the entire temperature range with a maximum ZTave of ∼0.03 at 300–923 K, which is nearly two orders of magnitude higher than that of printine La2CuO4. Our research has successfully developed the thermoelectric properties of La2CuO4‐based oxide, which has the great potential to be a reliable candidate as the thermocouple for high‐temperature detection in the key parts of aircrafts. [ABSTRACT FROM AUTHOR]

We report the detailed synthesis route of free-standing antiferromagnetic La2CuO4 nanoparticles by the sol-gel method. The precursors were needed to be dissolved in acid solution and continued with heating treatment to make a gel. Some catalyst was needed to control and stabilized the transformation from the solution to gel. Some heating treatments were also conducted to remove the organic component and for the nucleation process to obtain the single-phase sample. Although the sol-gel method required some additional precursors such as acid and catalyst, it has some advantages. It needed a relatively low sintering temperature and short sintering time compare to those at the solid-state reaction. Interestingly, this method can produce a sample with a good distribution of the particle size.

[Display omitted] • The partial substitution of La by Ba enhanced the thermal stability of La 2 CuO 4. • Ba addition caused structural changes creating oxygen vacancies on the surface. • XANES results showed the formation of Cu+ and Cu0 species during the reaction. • Prereduction improved catalytic activity by forming reduced species. • N 2 O is formed in lower yields as compared to noble metal-based catalysts. Catalytic reduction of NO by CO was studied over La 2-x Ba x CuO 4 (x = 0.0 or 0.4) mixed oxides prepared by coprecipitation method. The catalysts were characterized by X ray diffraction (XRD), O 2 temperature-programmed desorption (O 2 -TPD), H 2 temperature-programmed reduction (H 2 -TPR) and X-ray absorption near edge structure (XANES). NO + CO reaction was carried out in a fixed-bed flow reactor, from room temperature to 500 °C, at atmospheric pressure. Both fresh catalysts were active for the NO + CO reaction but when were submitted to thermal aging, the barium free catalyst significantly lost its activity. The partial substitution of La by Ba enhanced the thermal stability and although the activity of the catalyst has decreased, it remains high, approaching 100 % at 500 °C. These results can be associated with reducible copper species observed by XANES in the thermal aged catalyst containing Ba. [ABSTRACT FROM AUTHOR]

• La 2 Cu 1-x Co x O 4 (x = 0–0.15) perovskites synthesized via sol–gel autocombustion method. • XRD and FTIR confirm orthorhombic structure in prepared materials. • Optical energy bandgaps range from 1.31 to 1.04 eV, indicating semiconducting nature. • 15% Co-doped sample shows enhanced sunlight-driven methylene blue degradation. In this article, structural, optical and photocatalytic properties of a series of Co2+ doped La 2 CuO 4 perovskites, synthesized via sol–gel auto-combustion method, have been investigated for the first time. Structural and Fourier-transform infrared (FTIR) studies revealed pure orthorhombic phase formation with smaller crystallite sizes at higher Co2+ concentrations. Elemental composition was confirmed by energy-dispersive X-ray (EDX) analysis, and X-ray photoelectron spectroscopy (XPS) studies indicated the possible oxidation states of the constituent elements. The optical energy band gaps were estimated to be 1.31–1.04 eV, indicating the semiconducting nature and proper bandgap tuning with increased Co2+ content of the prepared perovskites. The highest photocatalytic methylene blue dye degradation efficiency, about 90%, was achieved for the 15% Co2+ doped La 2 CuO 4 perovskite, indicating its potential use as a photocatalyst for environmental remediation. [ABSTRACT FROM AUTHOR]

Solid polymeric electrolytes (SPEs) based on PVA/2wt% La2CuO4 with 5, 10 and 15 wt% of LiClO4 have been fabricated via solution intercalation technique. TEM result indicates that the size of nanoparticles (NPs) lies in the range 91–134 nm. The morphological behavior of PVA-SPEs probed by SEM; where the roughness of SPE films increased with increase in LiClO4 contents. The structural behaviors of SPEs have been elucidated by XRD, while ion-dipole interactions between components were evaluated by FTIR. The optical properties of SPEs investigated by UV-visible spectroscopy, where the outcomes showed increased refractive index from 1.74 to 2.41, whereas the band gap energy (Eg) is reduced from 5.26 to 3.32e V for PVA and PVA/2wt% La2CuO4/15wt%LiClO4, respectively. Electrical properties of the SPEs evaluated using LCR-meter at room temperature in frequency range 50 Hz–5 MHz. The ac-conductivity (σac) strongly depends on frequency and LiClO4 contents in SPEs and the maximum σac achieved is 2.82X10–5 Scm–1 for 15wt% LiClO4 doped PVA/La2CuO4 film. The current-voltage (I-V) data indicated non-ohmic behaviors at higher potential voltage region (> 6 V) and dc-conductivity (σdc) increased with increase in dosage of LiClO4 in SPEs through hopping ions mechanism. Thermal properties of the SPEs have been evaluated using DSC and TGA. The reduction in Tg of flexible SPEs with increase in LiClO4 content was observed due to amorphous portion dominates in SPEs. [ABSTRACT FROM AUTHOR]

The electrochemical CO 2 reduction reaction (CER) to methane (CH 4) has received great attention. Here, we proposed an efficient method to facilitate the conversion of CO 2 -to-CH 4 by creating a two-phase interface over urea-modified La 2 CuO 4 catalyst. The most optimized one exhibits the highest selectivity (22%) for CH 4 and the best activity (14 mA cm−2) and stability (5 h) at the potential of −1 V vs. reversible hydrogen electrode. The enhanced CER performance can be attributed to the establishment of interfacial effect within the two-phase, which facilitates the reduction of Cu2+ and promotes the active sites concentration. The 3 U-La 2 CuO 4 catalyst with La 2 O 3 /La 2 CuO 4 interfaces, which exhibits the highest selectivity (35%) for CH 4 and the best activity (14 mA·cm−2) and stability (5 h) at the potential of −1 V vs. reversible hydrogen electrode (RHE) in CER than La 2 CuO 4. [Display omitted] • 3 U-La 2 CuO 4 could be successfully synthesized by sol-gel method. • In 3 U-La 2 CuO 4 , La 2 O 3 is deposited on the of La 2 CuO 4 surface with two-phase structure. • The two-phase interface produced by 3 U-La 2 CuO 4 promotes the reduction of Cu2+. • 3 U-La 2 CuO 4 exhibits good CER activity with high stability. [ABSTRACT FROM AUTHOR]

ABO 3 -type perovskite oxides have been regarded as a kind of potential catalyst for peroxymonosulfate (PMS) activation. But some limitations such as specific pH conditions and coexisting ion interference restrict its practical application. Herein, a lanthanum copper Ruddlesden-Popper perovskite oxide (La 2 CuO 4) was successfully synthesized through the sol-gel process and applied in the activation of PMS. And for the first time the La 2 CuO 4 /PMS system was used for tetracycline hydrochloride (TC-HCl) degradation. Results showed that La 2 CuO 4 was a potential PMS activation catalyst in the removal of antibiotics. At optimized condition (0.2 g/L catalysts, 1 mM PMS, pH 0 6.9), 96.05% of TC-HCl was removed in 30 min. In experiments of debugging control conditions, over a wide pH range of 3–11, more than 90% of TC-HCl can be removed. In the natural water treatment process, TC-HCl removal rates of about 84.2% and 70.3% were obtained in tap water and River water, respectively. According to the reusability and stability tests and the results of FTIR and XPS analysis, La 2 CuO 4 had high structural and chemical stability. Electron paramagnetic resonance (EPR) suggested that the active species including · O H , S O 4 − · and 1 O 2 were detected in degradation reaction. Finally, reasonable reaction mechanisms and possible degradation pathways of TC-HCl were proposed. These results indicate that La 2 CuO 4 can act as a potential catalyst for PMS activation to degrade TC-HCl in water. [Display omitted] • La 2 CuO 4 was first applied in TC-HCl degradation by activation of PMS. • La 2 CuO 4 /PMS maintained high TC-HCl degradation efficiency in wide range of pH. • La 2 CuO 4 /PMS has great application potential in reagent water. • The reaction mechanism of La 2 CuO 4 /PMS/antibiotics degradation was studied. [ABSTRACT FROM AUTHOR]

For the first time, Cu-based perovskite oxides were used as catalysts to treat highly toxic and refractory petroleum refining wastewater based on catalytic wet peroxide oxidation (CWPO) technology. Perovskite La 2 CuO 4 was synthesized by sol-gel method. A series of characterizations showed that the synthesized catalyst particles are tetragonal phase perovskite structure. The experimental results showed that under the conditions of catalyst dosage of 0.75 g, temperature of 100 ℃ and reaction time of 30 min, the COD removal rate was 89.58 %, the TOC removal rate was 87.38 %. The morphology and structure of the catalyst before and after the reaction proved that the catalyst has strong stability and catalytic activity. The components of raw water, Wet Air Oxidation (WAO) effluent and CWPO effluent were compared and analyzed by Gas Chromatography-Mass Spectrometry (GC-MS), and the possible mechanism and path of WAO and CWPO degradation of petroleum refining wastewater were further explored. The changes of Cu components in La 2 CuO 4 before and after CWPO reaction and the transformation of lattice oxygen and adsorbed oxygen were analyzed by X-ray Photoelectron Spectroscopy (XPS). The involvement of Cu (Ⅱ) /Cu (Ⅰ) in the activation of H 2 O 2 was speculated. Finally, the biotoxicity of raw water, WAO effluent and CWPO effluent was predicted. The results provide reference value for the application of catalyst La 2 CuO 4 in various petrochemical wastewater. [Display omitted] • La 2 CuO 4 was first used as a catalyst in the CWPO process for wastewater treatment. • The catalyst La 2 CuO 4 shows strong catalytic activity and stability. • The synthesized catalyst particles had a tetragonal phase perovskite structure. • Under the optimum condition, the COD removal rate of CWPO effluent is 89.58 %. [ABSTRACT FROM AUTHOR]

[Display omitted] • Perovskite oxide LaMO 3-δ cathodes were applied for NO 3 –-N electroreduction. • La 2 CuO 4 exhibited best catalytic performance as its super electrochemical property. • The selectivity of NH 4 +-N and N 2 were 82.4 ± 2.2% and 9.4 ± 2.4%, respectively. • Both electron- and H*-mediated pathway occurred for NO 3 –-N electroreduction. • Oxygen vacancies and redox cycle of Cu(I)-Cu(II)-Cu(I) worked for NO 3 –-N reduction. Electroreduction removal of nitrate (NO 3 –-N) is considered as a promising approach to solve its adverse effects on environment and human health, where efficient and cheap catalysts are required. Perovskite-based catalysts showed a versatile catalytic ability for wide range of redox reactions, but seldom applied for NO 3 –-N reduction. Herein, four perovskite oxide cathodes, LaMO 3-δ (M = Fe, Co, Ni and Cu) were prepared and used for the reduction of NO 3 –-N. The Ruddlesden-Popper (RP) type La 2 CuO 4 exhibited the best NO 3 –-N catalytic activity among the four perovskite oxide cathodes, with a removal rate of 11.7 × 10-3 min−1. The high selectivity of NH 4 +-N (82.4 ± 2.2%) indicated that NH 4 +-N was the main final product for NO 3 –-N electroreduction at La 2 CuO 4 cathode, but 100% of N 2 selectivity could be obtained with addition of 1000 and 1500 mg/L Cl- as the electro-assisted chlorination process. The mechanism of NO 3 –-N electroreduction occurred by both electron- and H*-mediated pathway, and the oxygen vacancies and redox cycle of Cu(I)-Cu(II)-Cu(I) were proposed as the accommodation sties and direct electron sources for NO 3 –-N reduction. Generally, this study opens a novel avenue for the development of earth-abundant, cost-effective catalyst with effective NO 3 –-N electroreduction. [ABSTRACT FROM AUTHOR]

The gas phase dehydration of glycerol to hydroxyacetone was investigated over La2CuO4 catalyst under inert conditions. The reaction was performed in the temperature range of 260-400 °C. At low temperature (260 and 280 °C) high yields of hydroxyacetone can be achieved: 76% while at higher temperatures carbon deposition occurred. We showed that the structure of the La2CuO4 catalyst was modified during time on stream: Cu2+ was partially reduced into Cu1+ even at 260 °C. The formation of Cu2O was revealed by XRD and XPS analysis confirmed that both Cu2+ and Cu1+ are present at the surface of the catalyst. After reduction of La2CuO4 into Cu0/La2O3, low catalytic activity was observed proving that metallic copper is not the required species to perform the dehydration of glycerol into hydroxyacetone under our experimental conditions. TGA analysis revealed that only small amount of carbon deposition occurred during time on stream at 260 °C, no catalytic deactivation being observed during 20 h of reaction. [ABSTRACT FROM AUTHOR]

Abstract: This study describes the effects of YSZ addition on the response of potentiometric gas sensor based on La2CuO4 sensing electrode. The YSZ with four concentrations (0, 2, 5 and 10vol.%) are respectively added into La2CuO4 to enlarge the larger superficial area of the triple phase boundary (TPB). Obtained sensors are all highly sensitive to NO and NO2, but no responses to O2 and CO2. The biggest NO sensing is obtained by the sensor fabricated with 5vol.% YSZ addition at 400°C. This response behavior agrees with the scanning electron microscope and EDS spectrum results, indicating that appropriate superficial area of TPB can improve the sensor performance. In addition, the complex impedance of the sensor verifies that the triple phase boundary plays an important role on NO detection. Four sensors are all NO selective against O2, but their sensitivities are affected by CO2, CO and NO2. Interestingly, the response values and slopes of the sensor fabricated with 5vol.% YSZ addition are always bigger than those of the sensor fabricated with pure La2CuO4 in the cases of NO selectivity against CO2 and CO. [Copyright &y& Elsevier]

Abstract: A perovskite-like compound La2CuO4-based material, a well-known high-temperature superconductor, was studied as a photocatalyst. H2 was produced over La2CuO4 from aqueous solutions containing methanol as a sacrificial reagent under high-pressure Hg lamp irradiation. The photocatalytic activity of La2CuO4 is superior to that of the commercial anatase TiO2, and can be greatly improved by loading with Cu2O. Photoelectrochemical measurements revealed that the conduction band minimum of the La2CuO4 photocatalysts is thermodynamically feasible for the reduction reaction of water and Cu2O efficiently increase the electron–hole separation on La2CuO4 under photon irradiation to account for its higher photocatalytic activity. [Copyright &y& Elsevier]

Abstract: La2CuO4 and La2−xCaxCuO4 crystallites were prepared via a simple sol–gel process. The as-prepared La2CuO4 and La2−xCaxCuO4 crystallites were characterized by X-ray diffraction, transmission electron microscope and UV–vis–NIR spectra. Results show that the grain size of La2CuO4 crystallites increases with the increase of heat treatment temperature from 600°C to 800°C. Optical properties show that La2CuO4 crystallites have broad absorption both in the UV–vis region and in the NIR region. The band gap of the as-prepared crystallites decreases from 1.367eV to 1.284eV with the increase of calcination temperature from 600°C to 800°C. In the series of La2−xCaxCuO4 compounds (x=0.05, 0.08, 0.10, 0.12, 0.15 and 0.20), all of the samples exhibit an orthogonal crystal structure and the solubility limit of Ca2+ in La2CuO4 is within the range of x=0.12–0.15. In the whole UV–vis–NIR region, La2−xCaxCuO4 crystallites exhibit a broad absorption and the corresponding band gap first increases and then decreases with increasing of Ca2+ content. [Copyright &y& Elsevier]

Abstract: The effects of electrical contact configuration for La2CuO4 sensing electrodes for a planar-based potentiometric gas sensor were studied in order to further quantify the effects of processing on sensor performance. Five configurations of La2CuO4 were used for the sensing electrode. The La2CuO4 sensing electrode was screen printed opposite a Pt counter electrode on a tape cast YSZ electrolyte. Three sensors were prepared for each configuration to test repeatability. Each sensor was tested at temperatures from 400 to 700°C at various concentrations of NO2, NO, and CO in an environment of 3% O2 with a balance of N2. Results show that these sensors exhibit suitable sensitivity to all the gases tested. More importantly, it was shown that the sensitivity, selectivity/cross-sensitivity, and repeatability of these sensors are dependent on the sensing electrode configuration. [Copyright &y& Elsevier]

Abstract: The intent of this work is to look at the effects of varying the La2CuO4 electrode area and the asymmetry between the sensing and counter electrode in a solid state potentiometric sensor with respect to NO x sensitivity. NO2 sensitivity was observed at 500–600°C with a maximum sensitivity of ∼22mV/decade [NO2] observed at 500°C for the sensor with a La2CuO4 electrode area of ∼30mm2. The relationship between NO2 sensitivity and area is nearly parabolic at 500°C, decreases linearly with increasing electrode area at 600°C, and was a mixture of parabolic and linear behavior 550°C. NO sensitivity varied non-linearly with electrode area with a minima (maximum sensitivity) of ∼−22mV/decade [NO] at 450°C for the sensor with a La2CuO4 electrode area of 16mm2. The behavior at 400°C was similar to that of 450°C, but with smaller sensitivities due to a saturation effect. At 500°C, NO sensitivity decreases linearly with area. We also used electrochemical impedance spectroscopy (EIS) to investigate the electrochemical processes that are affected when the sensing electrode area is changed. Changes in impedance with exposure to NO x were attributed to either changes in La2CuO4 conductivity due to gas adsorption (high frequency impedance) or electrocatalysis occurring at the electrode/electrolyte interface (total electrode impedance). NO2 caused a decrease in high frequency impedance while NO caused an increase. In contrast, NO2 and NO both caused a decrease in the total electrode impedance. The effect of area on both the potentiometric and impedance responses show relationships that can be explained through the mechanistic contributions included in differential electrode equilibria. [Copyright &y& Elsevier]

Abstract: In order to further understand the different contributions to NOx sensing mechanism as well as the importance of electrode geometry, solid state potentiometric sensors with varying La2CuO4 sensing electrode thicknesses were studied. These sensors (with a Pt counter electrode) showed a dependence of NO2 sensitivity which decreased with increasing thickness in the temperature range of 550–650°C. They also showed NO sensitivity that was independent of thickness at 400°C and 600°C, but varied at temperatures between. This behavior was attributed to multiple mechanistic contributions explained by Differential Electrode Equilibria. [Copyright &y& Elsevier]

A new procedure to prepare oxides materials from oxalates complexes precursors is presented. Detailed description of the method is reported, illustrated with examples of the preparation of oxides. A solid-solid reaction between the oxalic acid and nitrate salt of metal leads to the formation of the corresponding oxalate. These oxalates are used as precursors and are heated to form the corresponding oxides by thermal-decomposition. This article relates the first examples of oxides prepared by this new method: the synthesis of the copper oxide CuO, the hexagonal phase of lanthanum oxide La2O3, and the lanthanum cuprate La2CuO4. All the samples are characterized by SEM and XRD. Thermal analysis TGA and DTA show the expected thermo-decomposition behavior for both copper and lanthanum oxalates. This study reveals also the formation mechanism of the cuprate La2CuO4 from the used precursor. [ABSTRACT FROM AUTHOR]

Abstract: The chemical reactivity of a novel cathode material for IT-SOFC, La2−xSrxCuO4−δ, with the oxide-ion conductor La0.83Sr0.17Ga0.83Mg0.17O3−w is investigated using XRD and ESEM/EDX techniques. La2−xSrxCuO4−δ samples (x=0.1 and 0.2) are prepared by citrate auto-combustion synthesis. The behaviour of mixtures of La2−xSrxCuO4−δ cathode material and La0.83Sr0.17Ga0.83Mg0.17O3−w (LSGM) electrolyte (1:1 weight ratio) annealed at 1000°C for 24–48h is studied. Peak broadening and shifting in the diffraction patterns are explained as diffusion of cations from one phase to the other; these findings are corroborated by the ESEM/EDX analysis. No diffraction peaks from reaction products are found. These results showed that the use of La2−xSrxCuO4−δ (x=0.1 and 0.2) cathode material in contact with LSGM electrolyte is not advantageous for SOFC application. [Copyright &y& Elsevier]

Nd2CuO4 and La2CuO4 are potential candidates as cathode material for intermediate temperature-solid oxide fuel cells. Nd–Cu and La–Cu oxides were co-sputtered on rotating substrates from metallic La, Nd and Cu targets in the presence of a reactive argon–oxygen gas mixture. Structural and chemical features of these films have been determined by X-ray diffraction and energy-dispersive spectroscopy. Their electrical resistivity was measured using the four-point probe method. As-deposited Nd–Cu based coatings are amorphous and, after annealing, crystallise in K2NiF4+ δ -type structure for Nd/Cu atomic ratio of 2, with more or less Nd2O3 or CuO, depending on whether Nd or Cu is in excess, respectively. As-deposited La–Cu based coatings are also amorphous and crystallise in La2CuO4 for La/Cu >2 or in LaCuO3± δ perovskite-type structure when Cu is in excess. The electrical measurements show a clear relation between resistivity and structure of the coatings. After annealing, crystallised neodymium-based coatings show higher resistivity than lanthanum-based ones. Finally, LaCuO3± δ exhibit higher resistivity than La2CuO4. [ABSTRACT FROM AUTHOR]

Three lanthanide cuprates Ln2CuO4 (Ln = La, Pr and Nd) have been studied in the CO + NO reaction. Under reaction conditions, a reduction of the cuprate was observed, with formation of metallic copper, which constitutes the active species in the reaction. After stabilisation, the resulting activity is lower when La in La2CuO4 is replaced by Pr or Nd. This decrease in activity has been related to a different reducibility of the cuprates, as shown by TPR under H2. When La is substituted by Pr or Nd, a higher temperature of formation of the copper active sites should induce the growth of bigger copper particles, which could be at the origin of the observed difference in activity. To cite this article: S.D. Peter et al., C. R. Chimie 7 (2004). [Copyright &y& Elsevier]

A large amount of static and dynamic NMR experiments have been carried out to determine the spin properties in high temperature superconductors cuprates (HTSC). In the majority of cuprates the magnetic shift at the planar copper nucleus is independent of the temperature when the field is applied perpendicular to the CuO2 planes and does not exhibit the expected reduction of the spin susceptibility in the superconducting state. This has been explained by a coincidental cancellation of on-site and transferred hyperfine fields at the copper nucleus, which would lead to a vanishing spin shift. To examine this explanation we determine the hyperfine fields by ab initio cluster calculations for La2CuO4 within the framework of spin-polarized density functional theory. In particular we investigate the sensitivity of the hyperfine fields on the lattice constants. [ABSTRACT FROM AUTHOR]

La2CuO4 is an active catalyst for the reduction of NO by CO. Under reaction conditions, the catalyst exhibits an activation which results in a lowering of the light off temperature by 80°C. XRD, TEM and EDX analysis carried out after the catalytic test indicate that the mixed oxide has been reduced to form a La2O3, Cu binary system. It seems that metallic copper species are the most active sites in the CO + NO reaction. [ABSTRACT FROM AUTHOR]

Reactivity of binary mixtures of oxalates of Cu(II) and La(III) was studied by observing their thermal behaviours in decomposition using TG, DTA and XRD techniques to set the temperature conditions for preparations of various composites of oxides of Cu(II) and La(III). In the thermal behaviour it was found that the decomposition of Cu(II) oxalate is not affected while that of La(III) oxalate is drastically affected in the case of all the mixtures. The decomposition temperature at which La(III) oxide is formed is lowered by 250 K in the case of all the mixtures while the complete decomposition occurred at 723 K only in the case of mixtures containing excess Cu(II) oxalate. At 823 K La2CuO4 phase is developed in all the mixtures while α-La and Cu2La phases are also detected in mixtures containing excess Cu(II) oxalate. Therefore, the temperature 823 K was found to be suitable to prepare various composites viz. La2CuO4, La2CuO4·La2O3 and La2CuO4·CuO to study their electrical properties. [ABSTRACT FROM AUTHOR]

Systematic neutron scattering measurements have been performed on the Sr-doped La{2- x}SrxCuO4 to study the doping dependence of spatially modulated dynamical spin correlations or so-called incommensurate spin fluctuations. The modulated spin correlations appear beyond x ≈ 0.05 which is close to the lower boundary of the superconducting phase. First evidence was observed for the linear relation between the degree of spatial modulation or the incommensurability Σ(x) and the maximum T c at x. We present a universal curve for Σ(x) by adding data from other La2CuO2 systems such as oxygen-doped superconductors, oxygen-reduced or Zn-substituted nonsuperconductors, and La1.6-xNd0.4SrxCuO4. [ABSTRACT FROM AUTHOR]

In single crystal La2CuO4+Σ,Σ ≈ 0.015, c-axis interstitial oxygen ordering (staging) in the oxygen-rich phase of the phase-separated sample was observed through satellite peaks in the neutron scattering which first appear at 250 K. If the sample is cooled through the temperature region around 210 K over a period of several hours, these satellite peaks show splitting in the a*-direction. This first-order phase transition involves a periodic one-dimensional modulation of the in-plane order. Microscopic modeling leads to a picture where the excess oxygen, and therefore also the doped holes, order in stripes along the a-direction in addition to staging along the c-direction. This ordering in stripes can be regarded as a continuation of the phase separation but now on a local scale, leading to a local increase in oxygen and hole density. This increase can account for the increase of the superconducting T c of 2.5 K observed in our sample and also for many previously reported annealing experiments. [ABSTRACT FROM AUTHOR]

Abstract: Using a two-step growth technique, simple oxide heterostructures have been fabricated by pulsed laser depositing epitaxial La2CuO4 (LCO) thin films on Nb-0.7wt%-doped SrTiO3 (NSTO) substrates. The junctions show good rectifying behavior at all measuring temperatures and an obvious temperature dependence of current–voltage (I–V) properties in the range of 25–300K, which are discussed in relation to the p–n model. [Copyright &y& Elsevier]

• La 2 CuO 4 -decorated ZnO was designed by in situ nanoparticle fabrication using SLE. • ZnO modification with La 2 CuO 4 can improve its photocatalytic activity. • Various characterization techniques were performed. • ZnO-La 2 CuO 4 exhibit excellent photocatalytic activity compared to ZnO and La 2 CuO 4. In this research, La 2 CuO 4 -decorated ZnO was designed by in situ nanoparticle fabrication using Strobilanthes crispus (B.) leaves extract (SLE) for the first time. To investigate the properties, La 2 CuO 4 -decorated ZnO were characterized by various characterization techniques. By a modification with La 2 CuO 4 , ZnO possesses the improved photocatalytic activity for malachite green degradation under visible-light illumination. ZnO-La 2 CuO 4 nanocomposites exhibit high photocatalytic activity compared to ZnO and La 2 CuO 4. The improved photocatalytic activity can be ascribed to the effect of the decreased bandgap value of the nanocomposite structure due to the low recombination of photogenerated electron-hole pairs. Furthermore, ZnO-La 2 CuO 4 shows good stability after three-run of photocatalysis experiment. The present research offers an eco-friendly and cost-effective method as an alternative for ZnO-La 2 CuO 4 nanocomposites fabrication with excellent photodegradation performance. [ABSTRACT FROM AUTHOR]

Amorphous thin films of La–Cu–O deposited by magnetron sputtering have been annealed at different temperatures and in situ analyzed by X-ray diffraction. These experiments were useful to determine the crystallization temperature and to follow the crystallization process of the film. The in situ annealing X-ray diffraction analyses have been also used to determine the thermal expansion coefficient of La2CuO4 thin film. The estimated value is close to that obtained for a commercial powder. The thermal expansion coefficient value with additional environmental scanning electron microscopy observations explains the delamination origin that occurs during the annealing before the crystallization step. The buckling and delamination of the film observed is caused by the thermal expansion coefficient mismatch of the film and the substrate. During the heating step, the mismatch generates compressive stress at the film/substrate interface, causing the film to lift off and crack in the typical way. [ABSTRACT FROM AUTHOR]

La 2 CuO 4 , a layered perovskites oxide was synthesized using solution combustion method at different calcination temperatures. XRD characterization and Rietveld refinement analysis confirms the pure phase of the synthesized material. The effect of calcination causes shrinking in the lattice parameters affirm the change in the oxygen stoichiometry. Four Probe (Van der Pauw's) and CP-AFM analysis were carried out to understand the influences of calcination temperature on electrical conductivity. Electrochemical investigations on La 2 CuO 4 were performed at various negative potential ranges using cyclic voltammetry (CV) to identify the redox active centre. Thermodynamic calculations are further carried out to validate the electrochemical results in different mediums. Selective electrocatalytic conversion of CO 2 to C 2 -hydrocarbon (C 2 H 4) with FE% of 40.3% which is 10 times higher than CH 4 (FE% = 4.1%) emphasized the in-situ formation of Cu 2 O from the redox active centre present in La 2 CuO 4. Hydrocarbons are generated at a very low overvoltage (−0.4 V RHE) in comparison to literature. XPS analysis indeed confirms the presence of Cu+ species i.e., in-situ generated Cu 2 O, on La 2 CuO 4 after CV and CO 2 electrocatalysis. Image 108061 • In the present study, we have explored the electrochemical behavior of redox active centre 'Cu2+' in a highly crystalline layered La 2 CuO 4 perovskite. • During electrochemical reduction, La 2 CuO 4 breaks into La 2 O 3 and Cu 2 O. This Cu 2 O further undergo reduction and forms Cu metal which is a reversible reaction. • Thermodynamic calculations aided in understanding the electrochemical in-situ formation of Cu 2 O. • Selective electrocatalytic reduction of CO 2 to C 2 H 4 (10 times higher than CH 4), at −0.4 V RHE, very low overpotential, emphasis the typical behaviour of Cu 2 O. • XPS analysis confirms the presence of Cu+ species (i.e., Cu 2 O) after electrochemical treatment of La 2 CuO 4 and retained after selective CO 2 electrocatalysis. [ABSTRACT FROM AUTHOR]

Abstract: The role of orbitals beyond the Cu 3d O 2p set employed in the widely used extended Hubbard model is considered with respect to low-energy charge excitations in cuprates. We focus on the description of the EELS and optical conductivity data of Sr2CuO3 and Sr2CuO2Cl2 with respect to O states. Consequences for the orbital character of doped holes are discussed. The achieved novel description of the EELS data in transverse chain response is robust with respect to the addition of Cu and 4s orbitals. [Copyright &y& Elsevier]