Synthesis-Dependent Surface Acidity and Structure of SrTiO₃Nanoparticles

Abstract

Chemisorption of pyridine and atmospheric CO 2 followed by means of visible Raman and DRIFT spectroscopy were employed to investigate the surface acidity and structure of as-prepared SrTiO 3 (STO) samples synthesized using three different approaches, solid-state reaction, molten salt, and sol-precipitation-hydrothermal treatment. Samples prepared via solid-state reaction consisted of irregularly shaped polycrystalline grains with a BET surface area of ∼2 m 2 /g, whereas those obtained via molten salt synthesis and sol-precipitation-hydrothermal treatment were single-crystalline nanocubes with the {100} faces primarily exposed and BET surface areas of ∼10 and 20 m 2 /g, respectively. Pyridine and atmospheric CO 2 chemisorption demonstrated that the differences in surface acidity between samples synthesized using different approaches are rather slight with a mixture of SrO-based and TiO-based terminations observed in all cases. In contrast, the typology of surface carbonate species arising from the reactive adsorption of atmospheric CO 2 varied significantly between samples, indicating the atomic structure of STO surfaces depends strongly on the synthetic method employed. The presence of coordinatively unsaturated Ti 4+ acid centers and highly nucleophilic O 2anions is particularly relevant in the perspective of employing morphology-controlled perovskite nanoparticles as supports in catalytic applications such as the oxidation of hydrocarbons.

Enhancement of thermoelectric power factor of hydrothermally synthesised SrTiO3 nanostructures

“…These modes arise due to the breaking of crystal symmetry. Such modes are assigned for the following O-Sr-O bending (244 cm −1 ), Ti-O-Ti bending mode (542 cm −1 ) and Ti-O stretching modes (736 cm −1 ) [22]. The presence of first order Raman lines in SrTiO 3 indicates the presences of different crystal symmetry.…”

Smart material concept: reversible microstructural self-regeneration for catalytic applications

“…However, a possible explanation could be given by a predominantly A-site terminated surface or a surface close to stoichiometry variation, such as titanium enrichment or nickel depletion due to nickel volatilization during sintering. [23][24][25] It has to be mentioned that only larger nanoparticle clusters could be easily identied and visualized due to the angular resolution of the SEM. Indeed, a more specic and careful SEM analysis revealed the existence of much smaller clusters at the exsolutionpreferred terrace steps, which is also attributed to very small nickel particles (Fig.…”

NaCl–H2O-assisted preparation of SrTiO3 nanoparticles by solid state reaction at low temperature

“…[5][6][7][8][9][10][11] Recently, a variety of SrTiO 3 nanoparticles with specific morphologies (e.g., nanocuboids, nanospheres, nanoparticles, nanosheets, nanowires, nanotubes, and microscale superstructures) have been prepared via high-temperature solidstate reaction, microemulsion, molten salt methods, hydrothermal or solvothermal methods, sol-gel methods, etc. [12][13][14][15][16][17][18][19] However, these methods suffer several problems associated with the environmental load and economical performance. Hydrothermal/solvothermal growth, sol-gel process, and precipitation have several disadvantages such as expensiveness of equipments and reagents, toxicity of the solvents, and complexity of the processes.…”