Perovskite Strontium Titanate Research Articles

Highly efficient La/Ni co-doped strontium titanate catalyst for co-production of propylene and hydrogen from propane in protonic ceramic electrochemical cells

A highly efficient La/Ni co-doped strontium titanate (LSNT) perovskite catalyst is developed and integrated in a protonic ceramic electrochemical cell for co-production of propylene and high-purity hydrogen from commercial propane feedstock. Propane conversion and hydrogen production rate can be effectively enhanced under an applied current due to the electrochemical promotion effect and/or shifted reaction equilibrium induced by rapid separation of hydrogen product. Water vapor in the feed gas could significantly improve the catalyst stability by suppressing the coke formation. The propane conversion could reach up to 53% at 600 °C under a current density of 90 mA cm−2. The LSNT catalyst also shows excellent tolerance for the sulfur contaminant in commercial propane gas. The excellent performance of the LSNT catalyst is attributed to the highly active and selective Ni species at the interface with the perovskite substrate, which are formed in situ via reduction-induced exsolution under reaction conditions.

Electrochemical syngas production over Au/SrTiO3 and Fischer–Tropsch synthesis chemistry for long-chain hydrocarbons

Syngas (a mixture of CO and H2) has been utilized in industrial settings for the production of liquid fuels through Fischer–Tropsch (F-T) synthesis. The conventional methods of producing syngas involve energy-intensive processes utilizing coal, natural gas, or biomass. However, in order to promote more environmentally friendly practices, electrochemistry has emerged as an alternative approach. In this study, we demonstrate that syngas can be efficiently produced through electrochemical (EC) CO2 conversion using Au-loaded perovskite strontium titanate (SrTiO3) as a catalyst. By manipulating various parameters such as overlayer Au thickness, applied potential, electrolyte type, and concentration, we can easily control the ratio of CO to H2. Moreover, our findings reveal that electrochemistry can directly initiate the minor channel of the F-T synthesis process. We also observe the occurrence of the EC F-T process in CO-saturated electrolyte, where CO molecules directly adsorb and interact with surface H to generate hydrocarbons. The analysis of the Anderson-Schulz-Flory equation demonstrates a strong linear relationship, confirming that the EC F-T synthesis follows the conventional F-T synthesis mechanism. This novel demonstration not only offers valuable insights into the development of EC syngas production but also enhances our understanding of the mechanism behind the formation of C2+ hydrocarbon products.

Catalytic Activity of Methane Oxidation on Nickel-doped Lanthanum Strontium Titanate Perovskite from Three Synthesis Methods

BackgroundThree perovskites of nickel-doped lanthanum strontium titanate (LSTN) were made and compared for their activity toward methane oxidation. MethodThe perovskite was synthesized separately via solid-state reaction, citrate complexation, and microwave-assisted methods. Significant FindingsThe perovskite from solid state reaction gave the highest activity of syngas production in repetitive redox cycles without any deterioration, demonstrating a great potential for use in chemical looping technology. Nevertheless, the material required activation in methane, as evidenced in studies of temperature-programmed surface reaction. On the contrary, the perovskite from the complexation method behaved completely different while the microwave-synthesized one gives the poorest activity. The variation of the activity was correlated with the distinct structure from different synthesis routes, which influences where a metal phase resides and how the metal anchors onto host oxides. The information obtained here would be of great benefit in making good material with desirable properties for catalysis and potential applications.

Amplified Dielectric Properties of PVDF-HFP/SrTiO3 Nanocomposites for a Flexible Film Capacitor.

A simple solution casting technique was used to fabricate perovskite strontium titanate (SrTiO3)-loaded poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) nanocomposite films for efficient energy storage applications. Various microscopic and spectroscopic methods were used to study the characteristics of the polymer nanocomposite films, like Fourier transform infrared spectroscopy (FTIR), X-ray diffraction technique (XRD), field emission scanning electron microscopy (FESEM), ultraviolet-visible spectroscopy, thermogravimetric analysis, and mechanical tensile test (stress vs strain). The FTIR, XRD, and FESEM analyses confirmed the incorporation and proper dispersion of SrTiO3 nanoparticles in the PVDF-HFP polymer matrix. An improvement in the optical, thermal, and mechanical behavior of the nanocomposite film was observed compared to the pure polymer. The values of dielectric constant, loss tangent, and AC conductivity of pure PVDF-HFP polymer and PVDF-HFP/SrTiO3 nanocomposites (2, 6, and 10 wt % SrTiO3 loadings) were analyzed in a temperature and frequency span of 30-150 °C and 1-100 kHz, respectively. To better understand the electrical properties of the materials, Nyquist plots were generated, and their related circuit designs were fitted. The 2 wt % SrTiO3 loaded nanocomposite exhibited the highest dielectric enhancement and AC conductivity compared to higher filler-loaded nanocomposites. This exceptional dielectric enhancement at very small filler loading is beneficial for commercialization and economically viable for real-time applications.

Evaluation of hyperfine interactions in strontium titanate perovskite for low doses of electron beam radiation

Evaluation of hyperfine interactions in strontium titanate perovskite for low doses of electron beam radiation

Gas sensing properties of graphene oxide loaded with SrTiO3 nanoparticles

This paper reports a straightforward and inexpensive method for the fabrication of gas sensing devices based on graphene oxide (GO) synthesized by a modified Hummer’s method and decorated with strontium titanate perovskite (SrTiO3). The active layers developed were employed for the detection of hazardous gases such as NO2, CO2, and NH3. The physical and chemical properties were also analyzed using various experimental techniques including field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and Raman spectroscopy. Repeated response and recovery cycles were applied in the detection of nitrogen dioxide (NO2), carbon dioxide (CO2), and ammonia (NH3). Accordingly, the gas sensing study reveals that decorated GO exhibits a high response towards NO2 at an operating temperature of 100 °C with good sensitivity (up to 4-fold higher than that of pristine GO) and highly improved selectivity. Additionally, the effect of ambient humidity was tested for NO2, demonstrating that GO/SrTiO3 sensors show a good immunity to humidity cross-sensitivity. Lastly, a gas sensing mechanism was schematically proposed and discussed. These findings prove that the functionalization of GO with SrTiO3 can overcome the limitations of GO-based sensors by enhancing their adsorption capability of gas molecules and their sensitivity towards target gases.

Strontium titanate perovskite embedded reduced graphene oxide photoanode for dye-sensitized solar cell

Simple chemical reduction process is followed to form strontium titanate perovskite nanoparticles (SrTiO3 NPs) embedded reduced graphene oxide nanocomposite (RGO-SrTiO3 NC). The optical band gap of the RGO-SrTiO3 NC is found as 3.24 eV. The XRD analysis reveals that the crystallite size of the RGO-SrTiO3 NC is considerably low (31.69 nm) when compared to the SrTiO3 NPs (56.93 nm). The Raman investigation establishes RGO existence in RGO-SrTiO3 NC. The C1s peak (285.02 eV) observed in the XPS spectrum of the RGO-SrTiO3 NC unveils modification of SrTiO3 by the RGO. The SEM examination indicate that the SrTiO3 NPs are embedded firmly on the RGO flakes by means of strong binding forces between RGO and SrTiO3 NPs. The SAED pattern of the RGO-SrTiO3NC is in agreement with its corresponding XRD pattern, confirming strong association between SrTiO3 NPs and RGO. The EDAX and elemental analysis of the RGO-SrTiO3 NC unveil existence of elemental peaks corresponding to Sr, Ti, C and O. The RGO-SrTiO3 NC exhibits significantly low PL intensity, indicating reduced charge recombination. The DSSC fabricated using the photoanode of RGO-SrTiO3 NC delivers an enhanced efficiency of 5.42% when compared to SrTiO3 NPs (2.59%) due to the presence of highly conducting RGO.

Suppression of intrinsic thermal conductivity in Sr1-x Gd x TiO3 ceramics via phonon-point defect scattering for enhanced thermoelectric application.

A substantial reduction in the thermal conductivity for strontium titanate (ABO3) perovskite structure was realized for the A-site substitution of gadolinium (rare earth element) in SrTiO3 ceramics. The effect of Gd3+ substitution on the structure, composition, and thermoelectric properties of SrTiO3 was investigated. The substitution of Gd3+ in the SrTiO3 matrix resulted in the minimalization of thermal conductivity. The thermal conductivity followed a similar trend as that of thermal diffusivity, but specific heat capacity exhibited a non-monotonic trend. The thermal conductivity is reduced to 1.05 W m-1 K-1 for the minimal substitutional composition (Sr0.99Gd0.01TiO3) which is 30% less than that of SrTiO3 at 303 K. The variation in the ionic radii and atomic mass of the heavier rare earth Gd3+ substituted over Sr2+ resulted in the reduction of thermal conductivity of SGTO ceramics caused by the corresponding boundary scattering at low temperatures and temperature-independent phonon-impurity scattering at high temperatures.

Defect-induced magnetism in homoepitaxial SrTiO3

Along with recent advancements in thin-film technologies, the engineering of complex transition metal oxide heterostructures offers the possibility of creating novel and tunable multifunctionalities. A representative complex oxide is the perovskite strontium titanate (STO), whose bulk form is nominally a centrosymmetric paraelectric band insulator. By tuning the electron doping, chemical stoichiometry, strain, and charge defects of STO, it is possible to control the electrical, magnetic, and thermal properties of such structures. Here, we demonstrate tunable magnetism in atomically engineered STO thin films grown on STO (001) substrates by controlling the atomic charge defects of titanium (VTi) and oxygen (VO) vacancies. Our results show that the magnetism can be tuned by altering the growth conditions. We provide deep insights into its association to the following defect types: (i) VTi, resulting in a charge rearrangement and local spin polarization, (ii) VO, leading to weak magnetization, and (iii) VTi–VO pairs, which lead to the appearance of a sizable magnetic signal. Our results suggest that controlling charged defects is critical for inducing a net magnetization in STO films. This work provides a crucial step for designing magnetic STO films via defect engineering for magnetic and spin-based electronic applications.

Evaluating the impact of substrate deposition on optical properties of perovskite barium strontium titanate (Ba0.5Sr0.5TiO3) thin films prepared by pulsed laser deposition technique

Evaluating the impact of substrate deposition on optical properties of perovskite barium strontium titanate (Ba0.5Sr0.5TiO3) thin films prepared by pulsed laser deposition technique

Structural, electronic, and optical properties of rare-earth-doped SrTiO3 perovskite: A first-principles study

The doping effect of the addition of rare earth elements (Pr, Nd, and Sm) on the mechanical and dielectric properties of the strontium titanate perovskite SrTiO3 was investigated using density functional theory (DFT). The introduction of rare earth elements modifies the structural properties and the charge distribution. Distortion of the Ti–O6 octahedron results in a decreasing trend in the mechanical and electronic properties with increasing nuclear charge numbers of Pr (59), Nd (60), and Sm (62). Rare earth element substitutions move the Fermi-level into the conduction band and change the absorption spectrum by adding peaks at 0.1–0.4 eV.

The study of nickel impurity segregation on LSNT perovskite open surfaces by means of ab initio molecular dynamics

In this paper, the segregation of the Ni impurity on open surfaces of the doped strontium titanate perovskite is investigated by means of ab initio molecular dynamics method based on the density functional theory and applied to a model periodic cell with stoichiometry La0.5Sr0.5TiO3 (LST).The performed studies are based on recent experimental observations on the segregation of Ni impurity atoms and their tendency to form clusters at the boundaries of defect structure of La0.2Sr0.7Ni0.1Ti0.9O3-δ (LSNT) perovskite. The results of the first-principles calculations of segregation energy showed that Ni does actively segregate toward the open surfaces. It was found that during segregation, nickel atoms leave the crystal volume to the perovskite surface and rise above its upper layer. Thus, the obtained results confirm the experimental data on the segregation and formation of nickel clusters on open LSNT surfaces.

Enhanced Photocatalytic Activity of Hydrothermally Synthesized Perovskite Strontium Titanate Nanocubes

Enhanced Photocatalytic Activity of Hydrothermally Synthesized Perovskite Strontium Titanate Nanocubes

Analysis of the Temperature Dependent Electrical Parameters of the Heterojunction Obtained with AU Nanoparticles Decorated Perovskite Strontium Titanate Nanocubes Analysis of the Temperature Dependent Electrical Parameters of the Heterojunction Obtained with AU Nanoparticles Decorated Perovskite Strontium Titanate Nanocubes

Analysis of the Temperature Dependent Electrical Parameters of the Heterojunction Obtained with AU Nanoparticles Decorated Perovskite Strontium Titanate Nanocubes Analysis of the Temperature Dependent Electrical Parameters of the Heterojunction Obtained with AU Nanoparticles Decorated Perovskite Strontium Titanate Nanocubes

Enhanced dye-sensitized solar cell performance using strontium titanate perovskite integrated photoanodes modified with plasmonic silver nanoparticles

Plasmonic silver nanoparticles loaded strontium titanate nanocomposites (Ag-SrTiO3 NC) with diverse weight percentages (0.5, 1.5, 2.5 and 5 wt%) of Ag nanoparticles (Ag NPs) are synthesized by a facile chemical reduction method. The prepared nanocomposites are characterized using diffuse reflectance spectroscopy, X-ray diffractometry, photoluminescence spectroscopy, scanning electronic microscopy and transmission electron microscopy. The photovoltaic performance of dye-sensitized solar cells (DSSCs) integrated with Ag-SrTiO3 NC photoanodes has been assessed under simulated sun light intensity of 100 mW cm−2. The Ag-SrTiO3 NC photoanode loaded with 2.5 wt% Ag NPs exhibited higher power conversion efficiency of 4.39% with short-circuit photocurrent density of 11.54 mA cm−2, open circuit voltage of 0.77 V and fill factor of 0.49 in DSSC. This enhanced photovoltaic performance can be credited to high dye loading, improvement in visible light harvesting - and fast photo-induced electron transfer caused by the plasmonic Ag NPs.

On the performance of polymer-inorganic perovskite oxide composite light-emitting diodes: The effect of perovskite SrTiO3 additives

This study reports the performances of a single structured light-emitting diode (LED) devices based on polymer material poly(9,9-di- n-hexylfluorenyl-2,7-diyl) (PHF) mixed with various concentrations of perovskite oxide strontium titanate (SrTiO3) particles deposited as a composite PHF: SrTiO3 emitting layer. The performances of the single structured organic LED indium tin oxide (ITO)/PHF/aluminum (Al) device and the composite LED ITO/PHF: SrTiO3/Al devices were compared in terms of turn-on voltage and luminance intensity. By incorporating perovskite SrTiO3 particles into PHF emitting layer, the turn-on voltage of the device is significantly reduced from 11.25 V to 1.80 V and the luminance intensity increased from 57.7 cd/m2 to 609 cd/m2. The improvement of turn-on voltage and the electroluminescence spectrum of the composite devices were found to be dependent on the weight ratios of SrTiO3 content in the PHF emitting layer.

Ultra-high extinction-ratio light modulation by electrically tunable metasurface using dual epsilon-near-zero resonances

The lossy nature of indium tin oxide (ITO) at epsilon-near-zero (ENZ) wavelength is used to design an electrically tunable metasurface absorber. The metasurface unit cell is constructed of a circular resonator comprising two ITO discs and a high dielectric constant perovskite barium strontium titanate (BST) film. The ENZ wavelength in the accumulation and depletion layers of ITO discs is controlled by applying a single bias voltage. The coupling of magnetic dipole resonance with the ENZ wavelength inside the accumulation layer of ITO film causes total absorption of reflected light. The reflection amplitude can achieve ~84 dB or ~99.99% modulation depth in the operation wavelength of 820 nm at a bias voltage of −2.5 V. Moreover, the metasurface is insensitive to the polarization of the incident light due to the circular design of resonators and the symmetrical design of bias connections.

Perovskite with in situ exsolved cobalt nanometal heterostructures for high rate and stable lithium-sulfur batteries

In order to solve the fundamental problem of polysulfide shuttle and slow reaction kinetics in lithium-sulfur batteries, we designed a novel adsorption-catalysis bifunctional heterostructure of strontium titanate perovskite and cobalt nanometal (STO@Co) prepared by in situ exsolution. Heterostructure can effectively adsorb polysulfides, which takes advantage of the ferroelectric effect of perovskite. After the in situ exsolution of Co nanometals, the exsolution of conductive metals enhance the conductivity of the heterostructure, while the in situ exsolved Co nanometal has excellent electrocatalytic activity and stability. Because of the superior interface compatibility between the in situ exsolved Co nanometal and perovskite, promote the synergy of adsorption-catalysis performance. The STO@Co electrode delivers higher specific capacity, better long-cycle stability, and rate capability compared to metal-impregnated perovskite heterostructure (STO/Co). This study proposes a new method of in situ exsolution for the preparation of heterostructures, which guides designing efficient battery materials.

One-step heating hydrothermal of iridium-doped cubic perovskite strontium titanate towards hydrogen evolution

A series of Iridium (Ir)-doped strontium titanate (SrTiO3) was successfully prepared for the first time by a one-step heating hydrothermal method for water splitting applications. An amount of Ir was incorporated into SrTiO3 structure at 210 °C and pH = 13 without any surfactant or stabilization addition. Compared to the pure SrTiO3 nanomaterials, the as-obtained Ir-doped SrTiO3 photocatalysts shows the significantly improved hydrogen evolution under ultraviolet irradiation and the highest activity with a hydrogen evolution rate of 1376 μmol.g−1.h−1 of the Ir-doped SrTiO3 photocatalyst with very low amount of doping Ir (1.0 wt%). The X-ray photoelectron spectroscopy (XPS) analysis confirms the existence of Ir4+ in accompany with Ir3+ on the surface, which could be assigned for the excellent performance of prepared materials. The successful synthesis of Ir-doped SrTiO3 not only introduces a new route to prepare a promoting material for hydrogenation evolution from water splitting under ultraviolet (UV) irradiation using methanol as a sacrificed agent, but also creates a preliminary step for high-performance Ir-doped SrTiO3.

Graphene/Strontium Titanate: Approaching Single Crystal–Like Charge Transport in Polycrystalline Oxide Perovskite Nanocomposites through Grain Boundary Engineering

AbstractGrain boundaries critically limit the electronic performance of oxide perovskites. These interfaces lower the carrier mobilities of polycrystalline materials by several orders of magnitude compared to single crystals. Despite extensive effort, improving the mobility of polycrystalline materials (to meet the performance of single crystals) is still a severe challenge. In this work, the grain boundary effect is eliminated in perovskite strontium titanate (STO) by incorporating graphene into the polycrystalline microstructure. An effective mass model provides strong evidence that polycrystalline graphene/strontium titanate (G/STO) nanocomposites approach single crystal‐like charge transport. This phenomenological model reduces the complexity of analyzing charge transport properties so that a quantitative comparison can be made between the nanocomposites and STO single crystals. In other related works, graphene composites also optimize the thermal transport properties of thermoelectric materials. Therefore, decorating grain boundaries with graphene appears to be a robust strategy to achieve “phonon glass–electron crystal” behavior in oxide perovskites.