Atomic‐Scale Insights into Surface Lattice Oxygen Activation at the Spinel/Perovskite interface of Co₃O₄/La_0.3Sr_0.7CoO₃

Abstract

Surface lattice oxygen in transition‐metal oxides plays a vital role in catalytic processes. Mastering activation of surface lattice oxygen and identifying the activation mechanism are crucial for the development and design of advanced catalysts. A strategy is now developed to create a spinel Co3O4 /perovskite La0.3Sr0.7CoO3 interface by in situ reconstruction of the surface Sr enrichment region in perovskite LSC to activate surface lattice oxygen. XAS and XPS confirm that the regulated chemical interface optimizes the hybridized orbital between Co 3d and O 2p and triggers more electrons in oxygen site of LSC transferred into lattice of Co3O4 , leading to more inactive O2− transformed into active O2−x. Furthermore, the activated Co3O4/LSC exhibits the best catalytic activities for CO oxidation, oxygen evolution, and oxygen reduction. This work would provide a fundamental understanding to explain the activation mechanism of surface oxygen sites.

Manipulating Surface Termination of Perovskite Manganate for Oxygen Activation

“…Moreover, the intensity of peak b increased significantly and the peak position also shifted to high binding energy, and this was attributed to higher covalence and increased MnO x surface segregations. High energy shifts for peak c suggested a transition from O 2 − species (O 1s → 3σ u ) to O 2 −1+x species (O 1s → 3σ u ), demonstrating that the surface lattice oxygen of B-LSM was successfully activated, [41] which is in agreement with the O 1s XPS results. In contrast to the O K-edge XAS, the Mn L 2 , L 3 -edge XAS in Figure 4d reveals no positional change for the absorption peak, whilst the white line intensity of B-LSM becomes weaker compared to A-LSM, suggestive of either low electron density for the Mn atom or high covalency for the MnO bond.…”

“…The perovskite surface usually contains suitable superoxide species and engineering of the surface electronic structure of perovskite catalysts to decrease this energy barrier is a significant research topic. [41] Our calculations reveal that Mn…”

“…Moreover, as shown in Figure 4a,b, and Figure S17, Supporting Information, the O 1s XPS peak of B‐LSM for the perovskite lattice termination also shifts to high energy, indicating the presence of more active lattice oxygen (O 2− x ) in B‐LSM. [ 41 ] These results clearly illustrate that B‐site termination can dramatically increase the activity of any surface oxygen species present and can promote the activation of molecular oxygen in oxidation reactions.…”

“…The O K‐edge and Mn L‐edge XAS were measured to study the spin state, covalent character of the bonding, and the electron density at the outer surface. [ 41 ] In Figure 4c,d, the O K‐edge and Mn L‐edge XAS for A‐LSM and B‐LSM are normalized from 518 to 557 eV and from 630 to 662 eV, respectively. As shown in Figure 4c, peak a and peak b at the O K‐edge are assigned as the hybridization between Mn 3d and O 2p; peak c is considered as a surface oxygen species; peak d derives from the hybridization between La 5d/ Sr 4d/ Mn 4sp and O 2p.…”

“…As shown in Figure 4c, peak a and peak b at the O K‐edge are assigned as the hybridization between Mn 3d and O 2p; peak c is considered as a surface oxygen species; peak d derives from the hybridization between La 5d/ Sr 4d/ Mn 4sp and O 2p. [ 41 ] Compared with A‐LSM, the peak a in B‐LSM shifts to a high binding energy and its peak intensity becomes weaker, which is ascribed to the enhanced covalency of the MnO bond. Moreover, the intensity of peak b increased significantly and the peak position also shifted to high binding energy, and this was attributed to higher covalence and increased MnO x surface segregations.…”