Although known in surface science field, surface reconstruction of perovskites has not been reaped for catalysis applications. In the past 5 decades, researchers have unsuccessfully attempted to relate catalytic properties of bulk mixed oxides to bulk properties of the crystal structure, such as the short metal-oxygen bond. This is due to the fact that the catalytic “stage”, i.e., the surface of a complex oxide can be different from the bulk in both composition and structure. In this work, we show for the first time how the surface reconstruction of perovskites, using SrTiO3 as an example, can be controlled to tune the catalytic selectivity in a wide range. The surface termination of the perovskite structure SrTiO3 (STO) was tuned via thermal pretreatment and chemical edging. The obtained surface terminations were found to impact the catalytic acid/base properties using the conversion of 2-propanol as a probe reaction. The surface of pretreated STO was characterized via multiple surface sensitive techniques, such as, low energy ion scattering (LEIS), methanol adsorption followed by FTIR, high angle annual dark field scanning transmission electron microscopy (HAADF-STEM) and microcalorimetry. Heat treatment above 500 °C under oxygen revealed Sr-enrichment of the surface and chemical edging with HNO3 revealed single and double-layer Ti-enrichment of the surface. A cooperative effect between acid and base sites is shown by a non-linear correlation between the rate of dehydrogenation/dehydration and the concentration of surface Sr/Ti. A wide range of selectivities toward propene or acetone was accessed after proper conditioning of STO; which is otherwise inaccessible using single metal oxides, SrO and TiO2. DFT calculations on Sr and Ti-terminated surfaces of STO explained the observed high selectivity toward propene for Ti-terminated surfaces and low selectivity for Sr-terminated surfaces. Similar catalytic tunability is also observed on BaZrO3 highlighting the generality of the findings from this work.

Selectivity control of acid-base reaction via surface reconstruction of perovskite catalysts

254th National Meeting (2017)

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