Nanoparticle (NP) exsolution from perovskite-based oxides
matrix
upon reduction has emerged as an ideal platform for designing highly
active catalysts for energy and environmental applications. However,
the mechanism of how the material characteristics impacts the activity
is still ambiguous. In this work, taking Pr0.4Sr0.6Co0.2Fe0.7Nb0.1O3 thin
film as the model system, we demonstrate the critical impact of the
exsolution process on the local surface electronic structure. Combining
advanced microscopic and spectroscopic techniques, particularly scanning
tunneling microscopy/spectroscopy and synchrotron-based near ambient
X-ray photoelectron spectroscopy, we find that the band gaps of both
the oxide matrix and exsolved NP decrease during exsolution. Such
changes are attributed to the defect state within the forbidden band
introduced by oxygen vacancies and the charge transfer across the
NP/matrix interface. Both the electronic activations of oxide matrix
and the exsolved NP phase lead to good electrocatalytic activity toward
the fuel oxidation reaction at elevated temperature.