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

Abstract

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 Fm3 @#x0305;m 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.