Epitaxial Domain of Pd Oxide with a Superperiodic Structure Formed on Sr3Ti2O7: A Promising Environmental Catalyst for Exhaust Gas Purification

The epitaxial growth of heterogeneous catalysts requires the use of highly crystalline metal oxide-based ceramics as catalyst supports. However, the catalytic applications of these ceramics are limited owing to their inherently low surface area. This study demonstrates that loading a very small amount of Pd species onto Sr3Ti2O7, a ceramic material synthesized via calcination of a precursor at 1273 K, leads to the formation of epitaxially bonded Pd oxide on the ab surface of Sr3Ti2O7. The Pd oxide particles with sizes ranging from 2 to 5 nm exhibit a superperiodic structure based on Fm (3) over barm space group, in which ordered and disordered Pd atoms are cyclically repeated along the a-axis of Sr3Ti2O7. Density functional theory calculations revealed that the charge transfer from Sr3Ti2O7 to Pd oxide facilitated the formation of an epitaxial junction and induced structural fluctuations within the Pd oxide. In addition, the Pd/Sr3Ti2O7 catalyst with a unique heterojunction exhibited excellent catalytic activity for the purification of automotive exhaust gases, despite its low surface area of only 2 m2 g-1. This study demonstrates that the catalytic potential of metal oxide-based ceramics can be realized through the precise engineering of the heterojunction interface.