SrTiO3 Nanoparticles Research Articles

Theoretical and experimental photocatalytic implications of Co ions upon the SrTiO3 lattice

SrTiO3 (STO) nanoparticles have been synthetized by the microwave-assisted hydrothermal (MAH) with the introduction of Co dopants in quotas of 0.5%, 1.0%,1.5% and 2.0% and the analytes were characterized by scanning electron microscopy (SEM), X-ray powder diffraction, Raman spectroscopy and UV/VIS techniques. The theoretical calculations have demonstrated that by the addition of Co ions the top of the valence band has been shifted to values above the potential energy for the formation of the OH– radical, a fact that indicates the defects as a hindrance to the conduction of the dye photo degradation steps. Although the band gap reduction being related to the amount of Co ions in the matrix the effect of recombination seemed to be augmented for the escalation of dopant material within the unit cell. The photocatalytic benchmark has demonstrated that the Co doping were directly related to the reduction on the reaction rate constant (k).

(Invited) Ferroelectric Effect in SrTiO3 Promotes Photoelectrochemical Water Oxidation

Ferroelectric materials, such as BaTiO3 or BiFeO3, retain an electric polarization after exposure to an external electric field. In semiconductor photoelectrodes, such a ferroelectric effect (FE) could be potentially used to enhance the carrier separation and photoelectrochemical activity under photoexcitation. However, to date, examples of FE-enhanced photoelectrochemistry are rare. Here, we report the discovery of a FE effect in oxygen vacancy rich SrTiO3 nanoparticles and single crystals, and their application for improved photoelectrochemical water oxidation. Single crystals terminated by [111] facets were subjected to hydrogen annealing at 1000 C to induce oxygen vacancies, as confirmed with optical absorption and X-ray photoelectron spectroscopy. In 0.5 M aqueous Na2SO4 solution 1.0 cm2 large crystals produce a 2.1 mA photocurrent at 0.6 V RHE and under 55 mW cm-2 UV illumination. Prior exposure to 10 kV cm-1 electric field increases the photocurrent to 4.5 mA or decreases it to 0.05 mA, depending on the orientation of the polarization. The effect of the electric polarization on the carrier separation direction is confirmed with surface photovoltage spectra. At room temperature, the FE in SrTiO3 is relatively short lived; samples stored in argon retain 85% of the FE effect after 24h, but samples stored in air loose 100% of the FE, likely due to oxygen uptake and disappearance of the vacancies. To obtain a microscopic interpretation of the observed FE effect we investigated ferroelectricity in oxygen-deficient SrTiO3 by density functional theory with effective many-body corrections. These calculations applied to SrTiO3 bulk and surfaces provide a rationale to interpret the experimental results. The finding of an FE in oxygen vacancy rich SrTiO3 is significant because it may be applicable to other metal oxides in the cubic perovskite structure type. Figure 1

SrTiO3/Ti3C2Tx Schottky heterojunction as a promising high-efficiency photocatalyst for H2 evolution

Exploring low-cost, high-efficiency, and stable photocatalysts is still a significant challenge. SrTiO3, one of the appealing photocatalysts, can meet most of the screening criteria except for its efficiency, which is restricted by its poor absorption of visible light and its prompt photogenerated carrier recombination. Recently, a two-dimensional transition metal carbide Ti3C2Tx (2D MXene) has been found to serve as a co-catalyst due to its excellent metallic conductivity, hydrophilic property, large specific surface area, abundance of active sites, and low reaction barrier to hydrogen production. In this work, SrTiO3 nanoparticles are rationally integrated with Ti3C2Tx nanosheets via a simple hydrothermal process. The hydrogen production rate can achieve up to 3.43 mmol g−1 h−1 in the hybridization of SrTiO3-3 wt. % Ti3C2Tx, which is almost six times that of SrTiO3 alone. This remarkable enhancement arises predominantly from the Schottky contact between SrTiO3 and Ti3C2Tx, which can effectively suppress the recombination of photogenerated carriers and accelerate their separation. In addition, such enhancement benefits from the hydrogen evolution capacity of Ti3C2Tx. This work opens an excellent prospect for constructing highly active, low-cost, and stable photocatalysts with 2D MXene and finding potential applications of 2D MXene in energy conversion fields.

Synthesis and Magnetic Properties of Carbon Doped and Reduced SrTiO3 Nanoparticles

We report on the studies of the synthesis, structural, and magnetic properties of undoped SrTiO3 (STO), carbon-doped STO:C, and reduced STO STO:R nanoparticles. Fine (~20–30 nm) and coarse (~100 nm) nanoparticles with a single phase of cubic perovskite-type structure were sintered by thermal decomposition of SrTiO(C2O4)2. Magnetization loops of fine STO:C and STO:R nanoparticles at low temperatures and an almost linear decrease in magnetization with temperature indicate the realization of a soft, ferromagnetic state in them, with a pronounced disorder effect characteristic of doped dilute magnetic semiconductors. Oxidation and particle size increase suppress the magnetic manifestations, demonstrating the importance of surface-related defects and oxygen deficiency in the emergence of magnetism. It was found that oxygen vacancies and doping with carbon make similar contributions to the magnetization, while complementary electron paramagnetic resonance, together with magnetization measurement studies, show that the most probable state of oxygen vacancies, which determine the appearance of magnetic properties, are charged F+ oxygen vacancies and C-impurity centers, which tend to segregate on the surface of nanoparticles.

Evaluation of the influence of SrTiO3 and CoO nanofillers on the structural and electrical polymer blend characteristics for electronic devices

Using the casting method, the films of nanocomposites (NCs) are made from a (PEOPVA) mixture with varying ratios of SrTio3 and CoO nanoparticles (NPs). The results show that increasing the ratio of (SrTiO3-CoO) NPs improved the electrical and structural characteristics of (PEO-PVA-SrTio3-CoO) NCs. The scanning electron microscopy results demonstrate that morphology on surface of the (PEO-PVA-SrTiO3-CoO) NCs is homogeneous and coherent, with several groupings or pieces distributing on the top of the surface at random. According to the dielectric characteristics, dielectric constant and dielectric loss of the NCs reduce with increasing the frequency of the applied electric field and increases with increasing concentration of (SrTiO3-CoO) nanoparticles. As the concentration of (SrTiO3-CoO) and frequency are increased, conductivity increases. The results of structural and electrical characteristics show that the (PEO-PVA-SrTiO3-CoO) NCs may be used for various electronics fields.

Boosting of structural, optical, and dielectric properties of PVA/CMC polymer blend using SrTiO3 perovskite nanoparticles for advanced optoelectronic applications

Hybrids of polymer-perovskite are attractive materials integrating improved physical and chemical properties with a pliability that presents them as fully suitable for electric devices and optoelectronic applications. In the current work, polymer nanocomposite (PNCs) films based on polymer blend matrix (i.e., polyvinyl alcohol (PVA)/carboxymethyl cellulose (CMC); 70/30 wt% weight ratio) reinforced with the solid-state reaction prepared SrTiO3 nanoparticles (NPs) were prepared using the solution casting technique. The crystallinity degree and chemical composition of the resulting samples were investigated by XRD and FTIR spectroscopy to study the influence of SrTiO3 on the blend structure and complexation with the functional groups of the hybrid PVA/CMC system. The SEM images showed a raise in surface roughness with the NPs content. Optical characteristics of PVA/CMC-SrTiO3 PNCs were examined using UV–Vis. Spectrophotometer. The optical gap (Eg) of the pristine PVA/CMC blend was boosted after loading SrTiO3 NPs. The influence of this perovskite on the ac conductivity, dielectric modulus and relaxation were discussed, where the dielectric constant of PNCs was higher than that of pure PVA/CMC preserving a low dielectric loss. From the experimental results, these PNC samples are promising for optical shielding, photosensors, advanced optoelectronics, photosensors, integral thin film capacitors, and high-density storage devices.

Fabrication of Mn-Doped SrTiO3/Carbon Fiber with Oxygen Vacancy for Enhanced Photocatalytic Hydrogen Evolution.

With carbon fiber, it is difficult to load semiconductor photocatalysts and easy to shed off thanks to its smooth surface and few active groups, which has always been a problem in the synthesis of photocatalysts. In the study, SrTiO3 nanoparticles were loaded onto the Tencel fibers using the solvothermal method, and then the Tencel fibers were carbonized at a high temperature under the condition of inert gas to form carbon fibers, thus SrTiO3@CF photocatalytic composite materials with solid core shell structure were prepared. Meanwhile, Mn ions were added into the SrTiO3 precursor reagent in the solvothermal experiment to prepare Mn-doped Mn-SrTiO3@CF photocatalytic composite material. XPS and EPR tests showed that the prepared Mn-SrTiO3@CF photocatalytic composite was rich in oxygen vacancies. The existence of these oxygen vacancies formed oxygen defect states (VOs) below the conduction band, which constituted the capture center of photogenerated electrons and significantly improved the photocatalytic activity. The photocatalytic hydrogen experimental results showed that the photocatalytic hydrogen production capacity of Mn-SrTiO3@CF composite material with 5% Mn-doped was six times that of the SrTiO3@CF material, and the doping of Mn ions not only promoted the red shift of the light absorption boundary and the extension to visible light, but also improved the separation and migration efficiency of photocarriers. In the paper, the preparation method solves the difficulty of loading photocatalysts on CF and provides a new design method for the recycling of catalysts, and we improve the hydrogen production performance of photocatalysts by Mn-doped modification and the introduction of oxygen vacancies, which provides a theoretical method for the practical application of hydrogen energy.

Efficient photocatalytic hydrogen production under visible-light irradiation on SrTiO3 without noble metal: dye-sensitization and earth-abundant cocatalyst modification

Efficient visible-light-driven H2 production without noble metal is one of the major challenges in photocatalysis. Herein, SrTiO3 nanoparticles synthesized from a facile hydrothermal process are adopted as supporting material for a fluorescein-sensitized photocatalytic system, and considerable H2 production is obtained without cocatalyst due to the relatively large surface area for sufficient adsorption of dye molecules. Upon further modification with earth-abundant Ni cocatalyst, the activity of H2 production from the as-established noble-metal-free fluorescein-sensitized photocatalytic system could be drastically enhanced, achieving an apparent quantum yield of ∼4.1% at 500 nm. The excellent photocatalytic performance is attributed to the synergistic contribution of the efficient electron excitation and injection, the significantly promoted charge transfer, and the abundant reactive sites provided by Ni cocatalyst.

Understanding targeted modulation mechanism in SrTiO3 using K+ for solar water splitting

Co-applying facet and defect engineering on SrTiO3 is critical to enhance the photocatalytic activity, and the Sr2+ vacancies contribute to the greater modulation capacity in A-site for designing defect engineering. Here, we use advanced characterizations combined with density functional theory to elucidate the origin of K-modulated facet and defect in SrTiO3 nanoparticles, thereby affecting the photocatalytic activities in overall water splitting. We found that the differences in binding strength between K2CO3 and different facets led to the exposure of non-equivalent facets. Based on the facet engineering, we demonstrated that the K-doping process consisted of filling and substitution process, and the lowest defect concentration existed at their intersection and with a maximum bending degree of surface energy band between {100} and {110} facets. The optimized 3%K-doped SrTiO3 composites have an intrinsic activity comparable to state-of-the-art catalysts. This work provides a significant theoretical guidance for rationally designing the high-performance SrTiO3-based photocatalysts.

Investigation on SrTiO3 nanoparticles as a photocatalyst for enhanced photocatalytic activity and photovoltaic applications

• For the first time Luminescence spectroscopy is employed to correlate the Phtocatalytic. study with Uv–Vis Spectroscopy. • SrTiO 3 annealed at 1000 °C shows high crystalline nature, low band gap and spherical. Morphology thermally stable. • Even after the three cycles of reuse , the catalyst retains its perovskite structure. • The photocatalytic efficiency is 36% and Power Conversion Efficiency is 1.12% is. achieved for the SrTiO 3 annealed at 1000 °C. The present work explores the effect of annealing temperature on the photocatalytic activity and power conservation efficiency (PCE) of the strontium titanate (SrTiO 3 ) nanoparticles. Various analytical tools are used to examine the crystalline structure, shape, size, bandgap, and emission characteristics of the synthesized SrTiO 3 . XRD results show that the crystallite size increased with increasing annealing temperature, which impacts the decrease of dislocation density and lattice strain. The fine agglomerated nanosphere morphologies and the elements presented in the sample are explored by SEM and EDX analysis along with mapping. TEM results also reveals spherical morphology with the inter-planer distance of 0.27 nm. Chemical valance states are confirmed with the XPS analysis. BET analysis reveals that STO6 possess Specific Surface Area of 20.971 m 2 g −1 .TGA confirms that the prepared material is stable up to 1000 °C. The methylene blue degradation result reveals that when increasing the annealing temperature, the photocatalytic degradation efficiency has increased. Among them, the STO6 sample is achieved the highest degradation efficiency of 36% at 120 min of irradiation which is 63% higher than the STO1 sample. The reusability of STO6 has been tested for three cycles and its structural stability also studied using XRD. Besides, the samples are served as a photoanode for dye-sensitized solar cells (DSSCs) and the results show that the STO6 cell delivered the highest short circuit current (J SC ) of 3.36 mA cm −2 , the open-circuit voltage (V OC ) of 0.63 V, and an efficiency (η) of 1.12%. According to the findings, the SrTiO 3 annealing temperature is also a crucial influence in determining photocatalytic activity and DSSC performance.

Semicrystalline SrTiO3 -Decorated Anatase TiO2 Nanopie as Heterostructure for Efficient Photocatalytic Hydrogen Evolution.

The coupling of TiO2 and SrTiO3 through elaborate bandgap engineering can provide synergies for highly efficient photocatalysts. To further improve the separation between photogenerated electrons and holes, a nano-heterostructured combination of semicrystalline SrTiO3 (S-SrTiO3 ) and anatase TiO2 nanoparticles is designed, and an optimized interface is achieved between uniformly grown S-SrTiO3 and metal organic framework (MOF)-derived anatase TiO2 through a controlled hydrothermal process. Besides tuning of the bandgap and broadening of the absorption spectral range, S-SrTiO3 particles alleviate charge carrier recombination benefiting from the coupling of the semicrystalline SrTiO3 around the interface. Additionally, highly dispersed S-SrTiO3 on TiO2 provides a good spatial distribution of active sites and the abundant carbon remained from MOF may reduce charge transport resistance. Moreover, the rapid transfer within the nano-heterostructure promotes the separation of the photogenerated charge carriers. With the above predominant architecture, when used as a photocatalyst, the as-synthesized S-SrTiO3 /TiO2 heterostructure exhibits exceptionally high photocatalytic performance of 13 005µmol h-1 g-1 for H2 production, exceeding most oxide-based photocatalysts reported. This study might provide mechanistic insights into a new perspective for the design and preparation of photocatalysts with novel structure and enhanced catalysis activity.

Energy storage performance of sandwich structure composites with strawberry-like Ag@SrTiO3 nanofillers

Recent years witness a rapid surge in the research efforts on dielectric capacitors due to their high power density and fast charge/discharge speed. However, the relatively low energy density demands more efforts to meet the lightweight and compact requirement for practical applications. Here, we report sandwich-structured nanocomposite films with strawberry-like Ag@SrTiO3 nanofillers. The introduction of Ag nanoparticles (NPs) on SrTiO3 NPs could significantly improve dielectric properties, breakdown strength, energy storage density, and efficiency. As a result, a dramatically enhanced discharged energy density (24.6 J/cm3) and efficiency (86.3%) are reached in sandwich-structured nanocomposite films containing 1.5 wt% Ag@SrTiO3 nanofillers by the solution casting method. The enhancement of dielectric constant and breakdown strength of nanocomposite films is attributed to the Coulomb-blockade effect of Ag NPs, which inhibits the transformation of electrons. Our finite element simulation explicitly demonstrates that the Coulomb-blockade effect of Ag NPs can effectively improve energy storage performance, which therefore supports the experimental results.

Solar light-induced injection of hot electrons and photocarriers for synergistically enhanced photothermocatalysis over Cu-Co/SrTiO3 catalyst towards boosting CO hydrogenation into C2–C4 hydrocarbons

Solar light-driven catalysis provides a viable approach for solar-to-chemical energy conversion, but it is difficult to maximize the conversion efficiency of solar energy through individual photocatalysis or photothermocatalysis. Herein, we construct a light-induced photo- and thermal-synergistic catalysis based on an adjacent Co and Cu nanoparticles co-loading on SrTiO3 nanoparticles. Under the irradiation of concentrated solar light, the SrTiO3 support is excited by ultraviolet light to induce photocatalytic effect to generate photocarriers; meanwhile, the localized surface plasma resonance-active Cu nanoparticles mainly absorb the visible-infrared light to produce hot electrons which are either quenched to generate heat or transported to active sites; finally, the active-phase Co nanoparticles converge the electrons and heat to drive CO hydrogenation into C2–C4 hydrocarbons. This study demonstrates that a rationally-designed catalyst can effectively convert solar energy to photocarriers/hot electrons and heat, and importantly, can couple them to regulate reaction pathways towards the production of value-added chemicals.

Preparation of SrTiO3 nanocubes by CO2 laser vaporization (LAVA) and hydrothermal maturation.

SrTiO3 is of particular interest for numerous applications such as photocatalytic water splitting, as an electrode material for thermoelectrics or as piezoceramics for sensors. Here we report on an advanced CO2 laser vaporization (LAVA) method for the production of faceted, single-phase SrTiO3 nanoparticles with an average particle size of 35 nm. Starting from a coarse SrTiO3 raw powder, spherical SrTiO3 nanoparticles were obtained by a laser-induced gas-phase condensation process. The composition of the nanoparticles corresponds to that of the starting powder, as XRD and FT-IR measurements show. Further hydrothermal treatment at 275 °C for 4 hours leads to the formation of faceted nanocubes with increasing crystallite size, as demonstrated by TEM, HR-TEM and XRD measurements. During a final washing step in 0.1 M HCl, SrCO3 impurities were dissolved and thus single-phase SrTiO3 nanocubes were successfully obtained, as shown by FT-IR, XRD and TEM analyses. The presented process facilitates the production of single-phase, highly crystalline SrTiO3 nanopowders in sufficient quantities for subsequent use in a variety of applications, in particular for hydrogen production by photocatalytic water splitting.

Sequential Synthesis Methodology Yielding Well-Defined Porous 75%SrTiO3/25%NiFe2O4 Nanocomposite.

In this research, we reported on the formation of highly porous foam SrTiO3/NiFe2O4 (100−xSTO/xNFO) heterostructure by joint solid-state and sol-gel auto-combustion techniques. The colloidal assembly process is discussed based on the weight ratio x (x = 0, 25, 50, 75, and 100 wt %) of NiFe2O4 in the 100−xSTO/xNFO system. We proposed a mechanism describing the highly porous framework formation involving the self-assembly of SrTiO3 due to the gelation process of the nickel ferrite. We used a series of spectrophotometric techniques, including powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), N2 adsorption isotherms method, UV-visible diffuse reflectance spectra (UV-Vis DRS), vibrating sample magnetometer (VSM), and dielectric measurements, to investigate the structural, morphological, optical, magnetic, and dielectric properties of the synthesized samples. As revealed by FE-SEM analysis and textural characteristics, SrTiO3-NiFe2O4 nanocomposite self-assembled into a porous foam with an internally well-defined porous structure. HRTEM characterization certifies the distinctive crystalline phases obtained and reveals that SrTiO3 and NiFe2O4 nanoparticles were closely connected. The specific magnetization, coercivity, and permittivity values are higher in the 75STO/25NFO heterostructure and do not decrease proportionally to the amount of non-magnetic SrTiO3 present in the composition of samples.

Inkjet-Printed Electron Transport Layers for Perovskite Solar Cells.

Inkjet printing emerged as an alternative deposition method to spin coating in the field of perovskite solar cells (PSCs) with the potential of scalable, low-cost, and no-waste manufacturing. In this study, the materials TiO2, SrTiO3, and SnO2 were inkjet-printed as electron transport layers (ETLs), and the PSC performance based on these ETLs was optimized by adjusting the ink preparation methods and printing processes. For the mesoporous ETLs inkjet-printed from TiO2 and SrTiO3 nanoparticle inks, the selection of solvents for dispersing nanoparticles was found to be important and a cosolvent system is beneficial for the film formation. Meanwhile, to overcome the low current density and severe hysteresis in SrTiO3-based devices, mixed mesoporous SrTiO3/TiO2 ETLs were also investigated. In addition, inkjet-printed SnO2 thin films were fabricated by using a cosolvent system and the effect of the SnO2 ink concentrations on the device performance was investigated. In comparison with PSCs based on TiO2 and SrTiO3 ETLs, the SnO2-based devices offer an optimal power conversion efficiency (PCE) of 17.37% in combination with a low hysteresis. This work expands the range of suitable ETL materials for inkjet-printed PSCs and promotes the commercial applications of inkjet printing techniques in PSC manufacturing.

Preparation, characterization and photocatalytic activity of SrTiO3 and Ag2O/SrTiO3 nanomaterials

The pure SrTiO3 nanoparticles were synthesized by sol-gel method and Ag2O loaded SrTiO3 (Ag2O/SrTiO3) was prepared by precipitation method. The obtained samples were characterized with powder X-ray diffraction (XRD), transmission electron microscope (TEM) and UV-visible diffuse reflection spectrum (DRS). The effect of Ag2O loading on the photocatalytic activity of Ag2O/SrTiO3 nanoparticles for the degradation of methyl orange (MO) as amodel pollutant under visible light irradiation was studied. Compared with pure SrTiO3 nanoparticles, the Ag2O/SrTiO3 nanoparticle displayed higher photocatalytic activity for the degradation of methyl orange and the 5 % Ag2O/SrTiO3 photocatalyst exhibited the highest photocatalytic activity.

Facet‐Dependent Surface Charge and Hydration of Semiconducting Nanoparticles at Variable pH (Adv. Mater. 52/2021)

SrTiO3 Nanoparticles The surface properties of different facets of SrTiO3 nanoparticles are investigated by atomic force microscopy by Frieder Mugele and co-workers in article number 2106229. Facet-specific forces, atomic-level surface structure, defects, and charges are characterized in a liquid environment. Their measurements reveal substantial differences in isoelectric points and hydration between adjacent facets. These insights are important for the performance of anisotropic nano particles in (photoelectron-) catalysis and for their colloidal self-assembly.

Facet-Dependent Surface Charge and Hydration of Semiconducting Nanoparticles at Variable pH.

Understanding structure and function of solid-liquid interfaces is essential for the development of nanomaterials for various applications including heterogeneous catalysis in liquid phase processes and water splitting for storage of renewable electricity. The characteristic anisotropy of crystalline nanoparticles is believed to be essential for their performance but remains poorly understood and difficult to characterize. Dual scale atomic force microscopy is used to measure electrostatic and hydration forces of faceted semiconducting SrTiO3 nanoparticles in aqueous electrolyte at variable pH. The following are demonstrated: the ability to quantify strongly facet-dependent surface charges yielding isoelectric points of the dominant {100} and {110} facets that differ by as much as 2pH units; facet-dependent accumulation of oppositely charged (SiO2 ) particles; and that atomic scale defects can be resolved but are in fact rare for the samples investigated. Atomically resolved images and facet-dependent oscillatory hydration forces suggest a microscopic charge generation mechanism that explains colloidal scale electrostatic forces.

Defect-induced modification of band structure by the insertion of Ce3+ and Ce4+ in SrTiO3: A high-performance sunlight-driven photocatalyst

Ce3+ and Ce4+ ions were successfully substituted in Sr2+ sites of SrTiO3 nanoparticles (NPs) synthesized by the Pechini type sol–gel process and post annealing at 750 °C. The resulting Ce-doped NPs, with average particle sizes up to 31.2 ± 0.5 nm, exhibited the cubic perovskite structure of SrTiO3. According to the analysis of crystalline structure, valence states, electronic structure, and optical properties, the surface defects induced by the Ce3+/Ce4+ pair had an important influence in improving the process of light absorption, charge transfer and surface chemisorption. Accordingly, the NPs with nominal composition Sr0.97Ce0.03TiO3 had the best balance between light absorption enhanced by surface defects and defect-induced carrier traps, exhibiting the highest photocatalytic activity with 95.10 % of methylene blue dye removal, after 120 min of simulated sunlight irradiation.