Although perovskites have been widely used in catalysis, tuning of their surface termination to control reaction selectivity in acid-base catalysis and promote methane activation has not been well established. Recent studies have shown that the surface of perovskite materials can be greatly different from the bulk in both composition and structure under different conditions, due to surface reconstruction. The present work shows how the surface termination of perovskites, using SrTiO3 (STO) as an example, can be controlled taking advantage of surface reconstruction after thermal treatment, chemical etching, incipient wetness impregnation and hydrothermal synthesis. The achieved surface terminations were characterized via multiple surface sensitive techniques. Controlling the termination of this perovskite catalyst allowed to tune the catalytic selectivity of acid/base reactions in a wide range, using the conversion of 2-propanol as a probe reaction. 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. In addition, enrichment of surface-Sr promoted higher rates for methane combustion, due to an increase in the density of the main active site for CH4 activation: stepped Sr site (as supported by high resolution microscopy, isotopic labeling kinetic experiments and DFT calculations). Similar catalytic tunability is also observed on BaZrO3, thus highlighting the generality of our findings.

Effect of the surface termination of perovskite catalysts on acid-base catalysis and methane activation

256th National Meeting (2018)

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