Abstract
Heterostructured oxides have shown unusual electrochemical properties including enhanced catalytic activity,
ion transport, and stability. In particular, it has been shown recently that the activity of oxygen electrocatalysis
on the Ruddlesden–Popper/perovskite
(La1-ySry)2CoO4±δ/La1–xSrxCoO3−δ
heterostructure is remarkably enhanced relative
to the Ruddlesden–Popper and perovskite constituents. Here we report the first atomic-scale structure and composition of
(La1–ySry)2CoO4±δ/La1–xSrxCoO3−δ grown on
SrTiO3. We observe anomalous strontium segregation from the perovskite to the interface and the Ruddlesden–Popper
phase using direct X-ray methods as well as with ab initio calculations. Such Sr segregation occurred during the film growth,
and no significant changes were found upon subsequent annealing in O2. Our findings provide insights into the design of highly
active catalysts for oxygen electrocatalysis.
# Graphical Abstract
