Synthesis-Dependent Surface Acidity and Structure of SrTiO3 Nanoparticles

Chemisorption of pyridine and atmospheric CO2 followed by means of visible Raman and DRIFT spectroscopy were employed to investigate the surface acidity and structure of as-prepared SrTiO3 (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 similar to 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 similar to 10 and 20 m(2)/g, respectively. Pyridine and atmospheric CO2 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 CO2 varied significantly between samples, indicating the atomic structure of STO surfaces depends strongly on the synthetic method employed. The presence of coordinatively unsaturated Ti4+ acid centers and highly nucleophilic O2- anions is particularly relevant in the perspective of employing morphology-controlled perovslcite nanoparticles as supports in catalytic applications such as the oxidation of hydrocarbons.