Perovskite LaNiO3 Research Articles

Gaps and pseudogaps in perovskite rare earth nickelates

We report on tunneling measurements that reveal the evolution of the quasiparticle state density in two rare earth perovskite nickelates, NdNiO3 and LaNiO3, that are close to a bandwidth controlled metal to insulator transition. We measure the opening of a sharp gap of ∼30 meV in NdNiO3 in its insulating ground state. LaNiO3, which remains a correlated metal at all practical temperatures, exhibits a pseudogap of the same order. The results point to both types of gaps arising from a common origin, namely, a quantum critical point associated with the T = 0 K metal-insulator transition. The results support theoretical models of the quantum phase transition in terms of spin and charge instabilities of an itinerant Fermi surface.

Experimental and kinetic investigation of the plasma catalytic dry reforming of methane over perovskite LaNiO3 nanoparticles

Plasma-assisted catalytic conversion of CH4 and CO2 into synthesis gas was performed in a dielectric barrier discharge reactor coupled with perovskite La–Ni nanoparticles (LaNiO3 NPs). Compared to supported catalysts such as Ni/γ-Al2O3, La–Ni/γ-Al2O3 and Ni/La2O3, LaNiO3 NPs showed better catalytic performance. The results show that the low flow rate of feed gases and high input power were favorable for the conversions of CH4 and CO2 as well as the selectivities of desired products, but led to lower energy efficiency. A global kinetic model according to argon dilution in plasma-catalytic system was proposed and employed to foresee the CH4 and CO2 conversion assisted by plasma-catalysts hybrid effect. The kinetic model indicates that the reactant conversion rate was an exponential function of the discharge energy.

Optimization of structural, surface and electrical properties of solution processed LaNiO3 conducting oxide

Growth, structural and electrical properties of perovskite type LaNiO3 thin film nanostructures using chemical solution deposition at annealing temperatures ranging from 550 to 800 °C has been optimized. Poly-vinyl alcohol was used as stabilizing agent in the precursor solutions. X-ray diffraction and AFM, respectively confirmed phase purity and nanostructured growth with mono dispersed crystallite distribution at processing temperature of 700 °C. Crystalline strain as low as 1 % was estimated from the XRD peaks; confirming relaxed and stable LNO crystalline structure deposited on quartz substrate. A systematic variation in the resistivity and carrier concentration with annealing temperatures were observed, revealing that 700 °C is an optimum temperature for a phase pure LNO films with smooth surface structures.

Nanocast LaNiO3 Perovskites as Precursors for the Preparation of Coke-Resistant Dry Reforming Catalysts

Dry reforming of methane is gaining great interest owing to the fact that this process efficiently converts two greenhouse gases (CH4 and CO2) into synthesis gas (CO + H2), which can be further processed into liquid fuels and chemicals. Herein, a perovskite-derived nanostructured Ni/La2O3 material is reported as an efficient and stable catalyst for this reaction. High-surface-area LaNiO3 perovskite precursor is first synthesized by the method of nanocasting using ordered mesoporous silica SBA-15 as a hard template. The resulting nanostructured perovskite was found to possess high specific surface area as obtained from the BET method (150 m2 g–1). The reduction behavior of the nanocast perovskite was monitored by performing the temperature-programmed reduction of hydrogen (TPR-H2). It has been found that the complete destruction of perovskite structure occurs below 700 °C, leading to the formation of highly dispersed Ni0 in La2O3, as observed in the XRD pattern of the material after reduction. Similar beha...

Chemical and morphological characterization of multi-walled-carbon nanotubes synthesized by carbon deposition from an ethanol–glycerol blend

The results of this work indicated that the carbonaceous material obtained by catalytic chemical vapor deposition (CCVD) method using a glycerol–ethanol mixture as carbon source and LaNiO3 perovskite as catalyst has grown in entangled tubular arrangements and corresponds to multi-walled carbon nanotubes (MWCNTs) which morphology features will depend on temperature conditions. Thus, at 700°C, thinner and well-defined MWCNTs with parallel graphene layers were observed, whereas at higher temperature (800°C and 900°C), bamboo-like MWCNT morphology prevails followed by an increase in their outer diameter. Although the last one is much more susceptible to oxidation in air compared to that obtained at 700°C, the packing of the graphene layers and the crystal size domain (La) along the axial axis of the nanotube corresponds to highly organized material being accord to that observed by transmission electron microscopy (TEM) and Raman spectroscopy. Therefore, the reactivity of bamboo-like MWCNTs to oxidation can only be explained by the presence of local defects associated with the interconnections between compartments.

Studies on B sites in Fe-doped LaNiO3 perovskite for SCR of NOx with H2

A series of LaNi1−xFexO3 (x = 0.0, 0.2, 0.4, 0.7, and 1.0) perovskites were synthesized and characterized by X-ray diffraction (XRD), N2 physisorption, scanning electron microscopy (SEM), H2-temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The perovskites were investigated for selective catalytic reduction of NOx by hydrogen (H2-SCR). It is shown that Fe addition into LaNiO3 leads to a promoted efficiency of NOx removal, as well as a high stability of perovskite structure. Moreover, easy reduction of Ni3+ to Ni2+ with the aid of appropriate Fe component mainly accounts for the enhanced activity. Meanwhile, deactivation of the sulfated catalysts is due to that sulfates mainly deposit on active Ni component while doping of Fe can protect Ni to some extent at the expense of partial sulfation.

Porous perovskite LaNiO3 nanocubes as cathode catalysts for Li-O2 batteries with low charge potential.

Developing efficient catalyst for oxygen evolution reaction (OER) is essential for rechargeable Li-O2 battery. In our present work, porous LaNiO3 nanocubes were employed as electrocatalyst in Li-O2 battery cell. The as-prepared battery showed excellent charging performance with significantly reduced overpotential (3.40 V). The synergistic effect of porous structure, large specific surface area and high electrocatalytic activity of porous LaNiO3 nanocubes ensured the Li-O2 battery with enchanced capacity and good cycle stability. Furthermore, it was found that the lithium anode corrosion and cathode passivation were responsible for the capacity fading of Li-O2 battery. Our results indicated that porous LaNiO3 nanocubes represent a promising cathode catalyst for Li-O2 battery.

Porous Perovskite LaNiO3 Nanocubes As Cathode Catalysts for Li-O2 Batteries with Low Charge Potential

In recent years, rechargeable lithium-O2 batteries with remarkably high theoretical energy storage capacity have attracted significant attention for applications in electric vehicles and energy storage of smart grids. However, for practical applications they still suffer from substantial challenges especially high charge overpotential caused by the sluggish oxygen evolution reaction(OER). Up to now, the most efficient OER catalysts are noble metals with high price and scarce quantity. Therefore, developing efficient OER catalysts with low price is essential for rechargeable Li-O2 battery. In our work, porous LaNiO3 nanocubes with porous structure and large specific surface area were employed as electrocatalyst in a Li-O2 battery cell. This catalyst showed high OER activity that could reduce the charge potential low to 3.40 V. The synergistic effect of porous structure, large specific surface area and high electrocatalytical activity ensures the Li-O2battery with enchanced capacity and good cycle stability. Furthermore, it is found that corrosion of lithium anode is also responsible for the capacity fading of Li-O2 battery, in addition to the passivation of oxygen cathode. Our finding indicated that porous LaNiO3 nanocubes can be recognized as a promising cathode catalyst for Li-O2 battery. Our work provided a perspective for the improvement of electrocatalyst performance in Li-O2 battery by tuning the structure of perovskite oxide.

The effects of partial substitution of Ni by Zn in LaNiO3 perovskite catalyst for methane dry reforming

A series of LaNi1−xZnxO3 (x=0.2, 0.4, 0.6, 0.8 and 1.0) perovskite-type oxides were synthesized via sol–gel related method by using propionic acid as solvent. The reaction was performed under continuous flow of feed stream which included CO2, CH4 and helium as diluting agent, under atmospheric pressure. The prepared catalysts were characterized by X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The results showed that the conversion rates of CO2 and CH4 increased as Ni was partially substituted by Zn. Considering the mentioned rates, among these catalysts, LaNi0.8Zn0.2O3 was the most effective catalyst. TPR results showed that partial substitution of Ni by Zn increased the temperatures of reduction peaks, leading to the more stable perovskite structure compared to LaNiO3 structure. It indicates that Zn stabilizes the perovskite structure. Also, TGA results showed that LaNi0.8Zn0.2O3 was more resistant to coke formation in comparison with LaNiO3 during 75h time on stream stability test.

Partial oxidation of methane over bifunctional catalyst I. In situ formation of Ni0/La2O3 during temperature programmed POM reaction over LaNiO3 perovskite

The transformation of perovskite to an oxide-supported metal during reaction of partial oxidation of methane (POM) has been very often cited in literature as the “reduction” of the perovskite, without any detailed mechanism. In this work, the in situ transformation of initial LaNiO3 perovskite to Ni0/La2O3 was studied under flowing CH4/Ar and CH4+O2/Ar (POM mixture) in temperature-programmed conditions. The catalyst was characterized before, during and after these experiments using X-ray diffraction (XRD), thermogravimetric analysis (TGA) and high resolution transmission electron microscopy (HRTEM/EDS) with Fast Fourier Transform (FFT) and Reverse FFT. Total oxidation of methane over LaNiO3 and lanthanum oxide (La2O3), as well as formation of syngas over the resulting Ni0/La2O3 catalysts, were studied for interpreting the three-step evolution of LaNiO3 to Ni0/La2O3, and evidencing NiO demixing from perovskite. A new global kinetic model of POM process over the final bifunctional Ni0/La2O3 catalyst was described.

Gas phase glycerol conversion over lanthanum based catalysts: LaNiO3 and La2O3

The catalytic performance of lanthanum based catalysts: LaNiO3 and La2O3 were evaluated in the gas-phase transformation of glycerol. The reaction was investigated in the temperature range of 300–700°C. At 400 and 500°C, the production of compounds in liquid phase is favored while at high temperature gases such as carbon monoxide, carbon dioxide and hydrogen are mainly formed. The basic catalysts used in this study favor the production of hydroxyacetone. Additionally 1,2 propanediol, methanol and ethylene glycol were formed in significant amount. The perovskite LaNiO3 and La2O3 show no significant deactivation during 10h at 400°C, the selectivity to hydroxyacetone only slightly decreased with time on stream most probably due to the formation of heavy products. The catalysts were characterized before and after reaction (XRD, TGA, CO2-TPD) showing that LaNiO3 was partially reduced into LaNiO2.5 during reaction at 400°C. It is suggested that strong basic sites of La2O3 compared to LaNiO3 are particularly active to produce methanol through glyceraldehyde but also acetaldehyde, propionaldehyde and acetone.

Catalytic performance of steam reforming of ethanol at low temperature over LaNiO3 perovskite

A LaNiO3 perovskite catalyst was prepared using the coprecipitation–oxidation hydrothermal method, followed by calcination at 600 °C for 2 h. The as-prepared sample was composed of La(OH)3 in nanorod structures and was covered with poorly crystalline Ni(OH)2. The mixed metal hydroxides were converted into cubic LaNiO3 perovskite after calcination at 600 °C. A catalytic steam reforming of ethanol (SRE) reaction for hydrogen production was performed in a fixed-bed reactor. The catalyst was reduced in situ in hydrogen at 400 °C prior to the reaction. The ethanol conversion reached 100% at 300 °C with 70% hydrogen selectivity. The highly catalytic activity of the reduced catalyst was due to the well-dispersion of Ni particles on the surface of active catalyst was formed in the in situ reduced catalyst. After a 80 h time-on-stream test at 350 °C, the used catalyst presented a La2O2CO3 component that was formed owing to the reaction of the CO2 product with La2O3. La2O2CO3 acted as a carbon reservoir to eliminate the deposited carbon and further stabilized the Ni particles on the La2O3 surface, which resulted in the highly catalytic activity during the entire reaction period. The deposited carbon after the SRE reaction was further examined by TGA, TPR, elemental analysis, and TEM.

Ni-Fe Catalysts Derived from Perovskite Precursors for Partial Oxidation of Methane

LaNi1-xFexO3 perovskites (x= 0, 0.2 and 0.4) were synthesized by the combustion method with urea and used as catalyst precursors in the partial oxidation of methane (POM). LaNiO3 was obtained as a single phase, while NiO and La(OH)3 were also detected in Fe-doped samples. The substitution of Ni by Fe in LaNiO3 perovskite resulted in a decrease in the specific surface area and an increase in the reduction temperature. The perovskite structure was completely decomposed by reduction, with formation of Ni°-Fe° and La2O3 phases. Activity cycles between 400 and 800°C revealed that the introduction of Fe decreased the catalytic activity for POM reaction at high temperatures. The catalysts showed great stability during 24 h on stream at 750°C without carbon deposition.

Synthesis of LaNiO3 perovskite by the modified proteic gel method and study of catalytic properties in the syngas production

This work describes a study on the synthesis of LaNiO3 perovskites via the modified proteic gel method, varying collagen content and on the catalytic activity of LaNiO3 and LaNiO3/Al2O3 in the syngas (CO + H2) production. X-ray diffraction patterns revealed the formation of perovskite structure in all samples prepared by proteic gel synthesis method, varying collagen content and after calcinations at 700 oC for 2 h. LaNiO3/Al2O3 catalyst prepared by the impregnation method showed diffraction peaks due to the perovskite structure and to the support (Al2O3). This catalyst presented: specific surface of 46.1 m2 g-1, two reduction peaks in the temperature programmed reduction (TPR) profile and 46% of methane conversion (by the partial oxidation of methane using oxygen) after 18 h of reaction.

A comparison study on methane dry reforming with carbon dioxide over LaNiO3 perovskite catalysts supported on mesoporous SBA-15, MCM-41 and silica carrier

The supported LaNiO3 perovskite catalysts on mesoporous carrier (LaNiO3/SBA-15, LaNiO3/MCM-41 and LaNiO3/SiO2) with different pore structures have been synthesized via filling the pores of mesoporous silica with citrate complex precursors of nickel and lanthanum, with further treatments. The catalysts were characterized by means of N2 physisorption, XRD, HRTEM+EDX, TPR, temperature-programmed hydrogenation (TPH) and TGA techniques, and their catalytic performances were measured in methane dry reforming with carbon dioxide to hydrogen and synthesis gas (syngas). The results of low-angle XRD, N2 physisorption and TEM analysis showed that LaNiO3 perovskite was formed inside the channels of mesoporous supports, and the introduction of LaNiO3 perovskite did not destroy the mesoporous structure of support. The pore structure had a substantial influence on the catalytic performance. LaNiO3/MCM-41 exhibited the higher initial catalytic activity, owing to the higher Ni dispersion, while LaNiO3/SBA-15 was superior to LaNiO3/MCM-41 in the long-term stability, which could be due to the stable silica matrix restricted the agglomeration of nickel species. The hexagonal mesopores of LaNiO3/SBA-15 were still kept intact after reaction, while the mesoporous structure in LaNiO3/MCM-41 was collapsed during the reaction, which resulted in metal particles aggregation to certain extent. For comparison, the carbon deposition was responsible for the remarkable decrease of catalytic activity over LaNiO3/SiO2 sample, evidenced by TGA and TPH results.

The influence of partial substitution of alkaline earth with La in the LaNiO3 perovskite catalyst

Abstract For enhancing the operation and increasing the activity of LaNiO3 catalyst in the reaction of dry reforming of methane, La was partially substituted by alkaline earth elements. The most effect was related to Ba with concentration of 0.1 (La0.9Ba0.1NiO3). XRD results showed that by adding alkaline earth the size of nickel particles is decreasing. Also, this test shows that adding Ba to the LaNiO3catalyst leading to the formation of La2NiO4 phase. There is a possibility that this phase plays a fundamental role in increasing the activity of the catalyst.

Effects of Partial Substitution of Ni by Cu in LaNiO3 Perovskite Catalyst for Dry Methane Reforming

A series of ternary perovskite type oxides LaNi 1- x Cu x O 3 ( x = 0.2, 0.4, 0.6, 0.8, and 1.0) were synthesized via the sol-gel method in propionic acid. Partial substitution of Ni by Cu showed higher activities and selectivities towards syngas products. LaNi 0.8 Cu 0.2 O 3 was the most active toward the CH 4 and CO 2 conversions, and was selective for syngas products. Temperature-programmed reduction results showed that the addition of Cu facilitates the reduction of Ni 3+ to Ni 0 , which is the main reason for the higher performance of this catalyst. The effect of Cu addition to LaNiO 3 as LaNi 1- x Cu x O 3 ( x = 0.2, 0.4, 0.6, 0.8, and 1.0) perovskite type oxides on the dry reforming of methane has been investigated. LaNi 0.8 Cu 0.2 O 3 showed the best performance with superior reduction of the nickel.

Effect of calcination temperature on structural properties and catalytic activity in oxidation reactions of LaNiO3 perovskite prepared by Pechini method

The study presented the preparation of the perovskite oxide LaNiO3 by the complex citrate method, paying particular attention to evolution of its formation from the amorphous precursor with varied calcination temperatures. The products obtained after heat treatment under air between 200 and 800 °C were characterized by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR), SBET measurements and X-ray photoelectron spectroscopy (XPS). The results showed the formation of a single phase with perovskite structure from ca. 550 °C. Tests on the two catalytic oxidation reactions of C3H6 and CO over the system calcined between mentioned temperatures were examined on the basis of characterization results and showed that optimum catalytic properties for such reactions were achieved for the perovskite calcined at 600 °C. In turn, correlations between redox and catalytic properties were established on the basis of thermogravimetric temperature programmed reduction (TPR) analysis.

Synthesis and catalytic activity of sol-gel derived La–Ce–Ni perovskite mixed oxide on steam reforming of toluene

Hybrid metal ion and polyvinyl alcohol (PVA) was prepared to obtain La1−xCexNiO3 (x = 0, 0.2, and 0.4) perovskite-type catalyst powder by sol-gel method. Metal ion to PVA monomer molar ratio was assigned at 1:1. The metal ion formed into complex precursors with alkoxide to improve the elemental dispersion and prevent agglomeration of obtained catalyst which is strongly related to activity and stability on syngas generation. As-prepared catalysts were calcined at 800 °C and characterized. X-ray diffraction pattern confirmed high crystalline of LaNiO3 perovskite structure and additional CeO2 phase was founded when La was partial substituted by Ce. The crystal size and particle size of La1−xCexNiO3 tended to decrease with higher Ce content. SEM and EDS results confirmed good elemental dispersion with homogeneous structure and low agglomeration. Particle size and surface area were in the range of 13.85–16.70 μm and 2.40–5.87 m2/g, respectively. Temperature programmed reduction (TPR) of prepared catalyst show highest H2 consumption at 390 °C and 700 °C which were attributed to the partial reduction of Ni3+ to Ni2+ and Ni2+ to Ni0, respectively. Activity of catalyst on steam reforming of tar was investigated using toluene as model compound in a fixed bed quartz reactor at 500–800 °C with steam/carbon molar ratio of 2:1. Carbon and hydrogen conversion were interpreted in term of CO2, CO, H2, and CxHy as CH4. The effect of operating temperature appeared to improve favorable fuel gas species formation in terms of selectivity and quantity. Addition of La0.6Ce0.4NiO3 catalyst promoted conversion of toluene to CO and H2 at the highest yield of 57.26% and 76.62% at 800 °C, respectively. Moreover, catalysts showed favorable stability because no deactivation was observed during the 180 min of test. LHV of syngas obtained can be used for power production without need for auxiliary fuel.

Use of Perovskite-Type Lanthanum Nickelate Synthesized by the Polymeric Precursor Method in the Steam Reforming Reaction of Methane

In the current work, LaNiO3 perovskite was synthesized using the polymeric precursor method. The materials were thermally treated at 300°C for 2 hours, subsequently supported on alumina or zirconia and finally calcined at 800°C for 4 hours. The resulting samples were characterized by X-ray diffraction, thermogravimetry, BET surface area and thermo-programmed reduction. Steam reforming reactions were carried out at 750°C and 6 bar during 4 hours using a pilot reactor under a H2O:CH4 ratio of 2.5. The mass of catalysts was about 5.7 g. X-ray diffraction patterns confirmed the formation of the perovskite structure in all samples prepared. The results also showed that lanthanum nickelate was more efficient when supported on alumina than zirconia. Finally, it was observed that the methane conversion was approximately 94% and the selectivity to hydrogen was about 70%. In all cases low selectivity to CO and CO2 was verified.