Co-doped Strontium Titanate Research Articles

High-Efficiency Photocathodic Protection of 304 Stainless Steel by F/N Co-Doped Strontium Titanate Photoanode Materials

High-Efficiency Photocathodic Protection of 304 Stainless Steel by F/N Co-Doped Strontium Titanate Photoanode Materials

Harnessing the electrocatalytic potential of in-situ exsolution of Ni nanoparticles on lanthanum and calcium co-doped strontium titanate for CO2 reduction in solid oxide electrolysis cells

The exsolution phenomenon of metal nanoparticles from a perovskite oxide involves the creation of oxygen vacancies, contributing to improved catalytic activity for CO2 reduction. In this context, a B-site Ni-doped and A-site La, Ca co-doped strontium titanate, denoted as La0.20Sr0.25Ca0.45Ni0.05Ti0.95O3-δ (Ni-LSCT), is synthesized with the aim of serving as a highly efficient cathode in conjunction with LSM as the anode and YSZ as the electrolyte for CO2 reduction via solid oxide electrolysis process. The incorporation of 5 mol% Ni doping at the B-site of the perovskite is successfully achieved, leading to the subsequent release of highly dispersed nanoparticles upon exposure to a reducing environment. YSZ-electrolyte-supported SOECs featuring the Ni-LSCT cathode demonstrate a notable current density of 0.93 A/cm2 at an applied voltage of 2.5 V at 800 °C in pure CO2. Moreover, at the same temperature, the reduction current density measures 1.21 A/cm2 when the Ni-LSCT serves as the cathode in a 70/30 molar ratio (CO2/H2) environment and 1.73 A/cm2 with a 50/50 molar ratio of the feed gas, both at an applied voltage of 2.5 V. This suggests an enhanced CO2 reduction performance in a reducing atmosphere. The introduction of Ni doping into LSCT enhances the electrochemical activity of the cathode by augmenting oxygen vacancies, while the presence of Ni nanoparticles on the cathode surface intensifies the active sites. Collectively, this innovative electrocatalyst configuration presents promising prospects for CO2 electrolysis within the SOEC framework.

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.

Colossal permittivity and low dielectric loss of Ta5+ and Al3+ co-doped strontium titanate ceramics sintered in N2 atmosphere

In this work, the ceramics of Sr(Ta1/2Al1/2)xTi1-xO3 (x = 0 %, 0.5 %, 1 %, 2 %, 3 %, 4 %, and 5 %) were produced through the solid-state reaction and sintered under N2 atmosphere. The frequency coefficient of permittivity and dielectric loss for the sample with x = 4 % is blow |24%| and |26%|, respectively, within the frequency of 1 kHz to 1 MHz. This demonstrates favorable frequency stability in the dielectric properties. The sample with x = 4 % exhibits remarkable permittivity (εr ∼ 125,000 @ 1 kHz, εr ∼ 95,000 @ 1 MHz) and low dielectric loss (tanδ ∼ 0.054 @ 1 kHz, tanδ ∼ 0.044 @ 1 MHz) were achieved at room temperature. Through the analysis of HAADF-STEM, XPS, it is concluded that and dielectric relaxation, the colossal permittivity effect is primarily attributed to defect clusters associated with oxygen vacancies such as Ti3+−VO••− Ti3+. The clusters of defect dipoles exert a pinning effect on freedom electrons, constraining their long-range transition and improving the dielectric properties. This study lays the foundation for advancing the electronic components, making a significant milestone in technological advancements.

An efficient particulate photocatalyst for overall water splitting based on scandium and magnesium co-doped strontium titanate

A high photocatalytic performance for overall water splitting was demonstrated over a photocatalyst based on a magnesium and scandium co-doped strontium titanate particle composed of a cubic shape having a nanosized step structure on the edge of the particle.

Properties of cobalt-doped SrTiO3 derived from two methods: the modified Pechini method and the citrate combustion method

Two wet-synthesis methods: citrate-combustion and modified (with PVA addition) Pechini synthesis were used to obtain Co-doped strontium titanate with assumed chemical compositions of SrTi1−xCoxO3 (where x = 0.02; 0.06; 0.10). All samples were calcined at 900 °C and sintered at 1200 °C, with PVA series being also calcined at 700 and 800 °C, since TG measurements indicated for this method materials lower minimal calcination temperature than for the citrate-combustion series materials. In general, the modified Pechini approach lowers calcination temperature of materials (up to 200 °C) and produces more structurally homogeneous materials than in the case of the citrate-combustion methods. However, the HT XRD measurements reveal the presence of extra cobalt oxide phases in pva_STO_xCo materials that were not visible using conventional XRD measurements. The presence of cobalt oxide has been confirmed for both series of materials based on TPR tests. Moreover, these measurements indicate the incorporation of some amount of cobalt into the perovskite structure. The fact of substituting titanium with cobalt in SrTiO3 structure seems to be confirmed by the results of XAS studies. Additionally, XAS results allowed us to state that Co2+/Co3+ ratio fell as cobalt loading increased in the materials. The examination of SrTiO3 lattice parameter changes for sintered samples is consistent with the findings of the XAS tests and indicates that cobalt adopts +2 oxidation state in the case of the material with the lowest Co content, and the share of Co3+ increases with the growth of the Co amount introduced into the system.

Reversibility limitations of metal exsolution reactions in niobium and nickel co-doped strontium titanate

Reversible metal exsolution and re-dissolution of metal cations in perovskite host lattices hold the potential for the development of regenerable metal-oxide catalysts. However, the reversibility of metal exsolution reactions is often limited.

Exsolution in La and Ni co-doped strontium titanate: a suitable anode for running SOFCs on ammonia as alternative fuel

Ammonia exhibits interesting features as fuel to feed Solid Oxide Fuel Cell. Herein, Ni and La co-doped strontium titanate was synthetized using wet chemistry route. Ni nanoparticles emerged via exsolution in reducing environment to decorate the surface. X-Ray Diffraction measurements exhibits perovskite structure was also preserved after the exsolution, as expected. H2 – Temperature Programmed Reduction highlights the great resistance of titanates in anode operation condition. Ammonia conversion in nitrogen and hydrogen were investigated by catalytic tests. It begins to decompose at 560°C and the full yield was achieved at 720°C. Electrochemical measurements were recorded at 800°C using 10% of ammonia in Ar. They were analysed though the model of equivalent circuit and two processes were attributed. Results certify Ni exsolution strongly enhances the hydrogen oxidation and the total polarisation resistance in ammonia approaches to the one in hydrogen.

Physical and Electrochemical Characterization of La0.25Sr0.25Ca0.40Ti0.95Ni0.05-xSnxO3–δ (x=0...0.05) Reversible Solid Oxide Cell Fuel Electrode

Redox stability and sulfur- or carbon tolerance of solid oxide fuel cell electrodes are deeply defined by the chemical composition of the materials 1-3. Therefore, much effort is invested in finding more chemically stable and electrochemically active materials. Generally, mixed ionic electronic conductor (MIEC) fuel electrodes offer better stability at the expense of lower electrocatalytic activity towards H2 and CO oxidation, whereas, exsolution of catalytically active nanoparticles may help increase the latter 4. Recently, excellent electrocatalytic performance has been demonstrated for lanthanum and calcium doped strontium titanate based MIEC materials in fuel cell and electrolysis modes 5,6.In this study, chemical stability and electrochemical performance of tin and nickel co-doped strontium titanate MIEC electrode materials (La0.25Sr0.25CaxTi0.9Ni0.50-ySnyO3–δ) were studied. Preliminary characterization included chemical stability studies followed by electrochemical characterization of most stable materials.All studied fuel electrode materials were synthesized using standard nitrate combustion method. All the single cells were prepared using commercially available 250 μm thick Zr0.89Sc0.10Ce0.01O2- d (10Sc1CeSZ, Kerafol) electrolyte support and La0.6Sr0.4CoO3- δ (LSC) oxygen electrode. Fuel and oxygen electrodes were sintered for 5 hours at 950°C and 900°C, respectively. Scanning electron microscopy, X-ray diffraction, FIB-TOF-SIMS and ICP-MS methods were used to characterize materials. Electrochemical characterization was carried out at temperature range from 700 to 850 °C in various H2O, CO2, H2 and Ar inlet concentrations.The chemical stability was greatly influenced by the A-site deficiency and B-site composition of the material as confirmed by comparing the FIB-TOF-SIMS data of as-synthesized and 100 hours reduced fuel electrode materials. Furthermore, as expected, a variation in Ni and Sn content resulted in large variations in studied single cell’s performances. Finally, the stability to the sulphur impurities in fuel electrode gas was investigated for some studied materials.

Diffusion kinetics mechanism of oxygen ion in dense diffusion barrier limiting current oxygen sensors

Limiting current oxygen sensors based on strontium titanate composites have been prepared and their physical properties were investigated in details. B-site deficient yttrium and iron co-doped strontium titanate was prepared to scrutinize the contribution of electronic and ionic features on the electrical conductivity and investigate oxygen ions diffusion in the barrier layer. The mixed conductivity and sensing properties of the aforementioned materials were attentively studied in order to identify the impact of B-site deficiency on the SrTiO3-based dense diffusion barrier and therefore performance of the fabricated limiting current oxygen sensors. The obtained results demonstrated that the total conductivity conspicuously increased and the ionic conductivity decreased upon an augmentation in the content of B-site deficiency. The increase of B-site deficiency can accelerate the occurrence of limiting current of the sensors at lower voltages and then elevate the service life of the sensor and promote an independence relationship between limiting current and temperature. Y-doping affects interatomic force in the crystal structure of Y0·08Sr0·92(Ti0·6Fe0.4)0.97O3-δ and therefore, reduces the diffusion rate of oxygen vacancy which is favorable for development of limiting current oxygen sensor.

Highly improved thermoelectric performance of Nb-doped SrTiO3 due to significant suppression of phonon thermal conduction by synergetic effects of pores and metallic nanoparticles

A remarkable thermoelectric performance in oxide materials was achieved by Nb and Ni co-doped strontium titanate (STNNO) containing pores and Ni nanoparticles. A combined structure of macroporus matrix and the Ni nanoparticles was realized by an exsolution reaction of metallic Ni from the porous STNNO matrix. The porous nanocomposite structure led to a substantial decrease in the thermal conductivity down to 1.4 W m−1 K−1 at 800 °C, and a moderate improvement of the electrical properties. As a result, the porous nanocomposite structure containing the metallic Ni nanoparticles significantly decreased the phonon thermal conductivity to 0.91 W m−1 K−1 at 800 °C, resulting in a remarkable ZT of 0.60 at 800 °C for STNNO reduced in 20% H2/N2.

Development of Epitaxial Thin Film Model Electrodes for the Systematic Investigation of Metal Exsolution from MIEC Perovskite Oxides

Metal exsolution of catalytically active B-site dopants of mixed ion and electron conducting (MIEC) perovskites under reducing conditions can be utilized for the preparation of high-performance electrode materials. To study the underlying mechanisms of the exsolution process with respect to specific material aspects - for example structural properties of the host lattice - advanced model systems with well-defined properties are required. Pulsed laser deposition (PLD), enables the fabrication of such model electrode systems by epitaxial growth of complex oxides with highly defined and tunable structural properties. In this study, we present the development of epitaxial model electrodes of Nb and Ni co-doped strontium titanate (SrTi0.9Nb0.05Ni0.05O3-δ, STNNi) by PLD. We discuss epitaxial growth and material properties providing well-defined thin film model electrodes suitable for the investigation of nanoparticle exsolution.

Giant dielectric response in (Nb + Zn) co-doped strontium titanate ceramics tailored by atmosphere

Effects of sintering and annealing atmosphere on the defect structures and the dielectric behaviors of (Nb + Zn) co-doped SrTiO3 ceramics are systematically investigated. Giant permittivity (~50,100), low dielectric loss (~0.04) and wide temperature (25–330 °C)/frequency (20–105 Hz) stabilities are achieved in the N2 sintering ceramics. Further investigations indicate massive defects and defect clusters are involved, contributing to the giant permittivity. The associated defects not only restrain the ionization of oxygen vacancy, but also localize the motions of oxygen vacancy and electron, resulting in the low dielectric loss and the suppressed relaxation peaks.

Characterization methods of nickel nano-particles obtained by the ex-solution process on the surface of Pr, Ni-doped SrTiO3 perovskite ceramics

In this paper, a novel electrode material based on Pr, Ni co-doped strontium titanate (Sr0.7Pr0.3)xTi1−yNiyO3 with constant amount of 30% praseodymium dopant, different amount of nickel (y = 0.06 and y = 0.10) and additional nonstoichiometry in Sr-site (x = 1; x = 0.9 and x = 0.8) was investigated as fuel electrode for SOEC devices. A porous ceramics were prepared by solid-state reaction method. X-ray diffraction measurements revealed single phase materials with perovskite structure. Ex-solution method makes the grain surface covered by nickel nanoparticles. The influence of nickel amount, non-stoichiometry, synthesis and reduction conditions on formation of nanoparticles was investigated. Size, distribution and ability to agglomeration of Ni nanoparticles were analyzed by the scanning electron microscopy. The quantity of ex-soluted Ni particles was calculated from magnetization measurement. The total electrical conductivity of samples was measured by DC 4-wire method in the range of 100–800 °C at different atmospheres. Electrical measurements showed total electrical conductivity higher than 10 S cm−1 in a wide temperature range. All obtained results confirmed that analyzed donor and acceptor co-doped SrTiO3 materials with Ni nanoparticles after ex-solution process should be a good candidate to improve a catalysis process on fuel electrode surface.

Constructing Implantable SrTiO3 :Yb,Ho Nanofibers for NIR-Triggered and Optically Monitored Chemotherapy.

Light-responsive and photoluminescent (PL) drug-delivery platforms have sparked fascinating advancements in personalized tumor chemotherapy due to their unique characteristics in biological imaging and manipulated release kinetics. Herein, implantable Yb3+ and Ho3+ co-doped strontium titanate (SrTiO3 :Yb,Ho) nanofibers were synthesized and decorated on the surface with polyacrylic acid (PAA) molecules. The preliminary in vitro assay confirmed that this implantable fibrous mesh presented sound cytocompatibility. The PAA surface decoration improved the loading capacity of an anticancer drug (doxorubicin (DOX)) and effectively prevented a daunting burst release in a neutral aqueous environment. Owing to the electrostatic bond between PAA and DOX molecules, low-pH microenvironments and NIR (λ=808 nm) irradiation both induced significantly accelerated DOX release and consequently enhanced the local cancer-cell-killing effect. Additionally, the ratio of green-to-red emission (I545 /I655 ) from the SrTiO3 :Yb,Ho-PAA fibers responded effectively to the DOX release progress and dosage due to a fluorescence resonance energy transfer (FRET) effect. This unique characteristic enabled optical monitoring of the delivery progress in a timely manner. These SrTiO3 :Yb,Ho-PAA nanofibers, with precise dual-triggering and optical monitoring of DOX release, are expected to serve as a new implantable drug delivery platform for personalized chemotherapy in the future.

A Solid Oxide Fuel Cell with Lanthanum and Calcium Co-Doped Strontium Titanate as Support

Alternative anodes are of great interest for robust solid oxide fuel cells (SOFCs). A-site deficient strontium titanate co-doped with lanthanum and calcium, La0.2Sr0.25Ca0.45TiO3 (LSCTA-), has been investigated as a potential anode for SOFCs. Flat multilayer ceramics have been produced by controlling the sintering behavior of LSCTA-, resulting in a 450 µm thick porous LSCTA- scaffold with a well adhered 40 µm dense YSZ electrolyte. Impregnation of CeO2 and Ni has resulted in power densities of 0.96 Wcm-2 at 800 oC, higher than 0.125 Wcm-2 without impregnation and 0.38 Wcm-2 for Ni alone, demonstrating encouraging performance. Work continues to improve understanding of catalyst-scaffold interactions and scaling up the concept.

Electrochemical Performance of YST Infiltrated and Fe Doped YST Infiltrated YSZ Anodes for IT-SOFC

Donor doped and donor-acceptor co-doped strontium titanate perovskite are investigated for intermediate temperature solid oxide fuel cells (IT-SOFCs) anodes. Y0.08Sr0.88TiO3-δ and Y0.08Sr0.92Ti1-xFexO3-δ (x = 0.2, 0.4) anodes were prepared by infiltration in 65% porous yttria stabilized zirconia (YSZ) scaffolds. The microstructure and electrical conductivity of Y0.08Sr0.88TiO3-δ and Y0.08Sr0.92Ti1-xFexO3-δ stronglydependsonFecontent.TheconductivityofY0.08Sr0.88TiO3-δ andY0.08Sr0.92Ti1-xFexO3-δ;decreases with increasing Fe content in humidified H2 .Y 0.08Sr0.88TiO3-δ ,Y 0.08Sr0.92Ti0.8Fe0.2O3-δ ,a nd Y0.08Sr0.92Ti0.6Fe0.4O3-δ, anodes with aP d/CeO2 catalyst show peak power density of 298, 421, and 321 mW cm −2 , respectively, in wet H2 at 1073 K.

Green and red upconversion luminescence in Er 3+-doped and Er 3+/Yb 3+-codoped SrTiO 3 ultrafine powders

Er 3+-doped and Er 3+/Yb 3+-codoped strontium titanate (SrTiO 3) ultrafine powders were prepared in a molten NaCl flux. The intense green and red emissions around 528 nm, 550 nm and 662 nm corresponding to the 2H 11/2 → 4I 15/2, 4S 3/2 → 4I 15/2 and 4F 9/2 → 4I 15/2 transitions, respectively, of Er 3+ ions were observed under excitation at 980 nm. A great enhancement of the visible upconversion emissions in Er 3+/Yb 3+-codoped sample was observed. Excited state absorption and energy transfer process are discussed as the possible mechanisms for these emissions.