Cation Segregation of A‑Site Deficiency Perovskite La_0.85FeO_3−δ Nanoparticles toward High-Performance Cathode Catalysts for Rechargeable Li‑O₂ Battery

Cation segregation of perovskite oxide is crucial to develop high-performance catalysts. Herein, we achieved the exsolution of α-Fe₂O₃ from parent La_0.85FeO_3−δ by a simple heat treatment. Compared to α-Fe₂O₃ and La_0.85FeO_3−δ, α-Fe₂O₃-LaFeO_3–<i>x</i> achieved a significant improvement of lithium-oxygen battery performance in terms of discharge specific capacity and cycling stability. The promotion can be attributed to the interaction between α-Fe₂O₃ and LaFeO_3–<i>x</i>. During the cycling test, α-Fe₂O₃-LaFeO_3–<i>x</i> can be stably cycled for 108 cycles at a limited discharge capacity of 500 mAh g^–1 at a current density of 100 mA g^–1, which is remarkably longer than those of La_0.85FeO_3−δ (51 cycles), α-Fe₂O₃ (21 cycles), and mechanical mixing of LaFeO₃ and α-Fe₂O₃ (26 cycles). In general, these results suggest a promising method to develop efficient lithium-oxygen battery catalysts via segregation

Activation of Surface Oxygen Sites in a Cobalt-Based Perovskite Model Catalyst for CO Oxidation

Anionic redox chemistry is becoming increasingly important in explaining the intristic catalytic behavior in transition-metal oxides and improving catalytic activity. However, it is a great challenge to activate lattice oxygen in noble-metal-free perovskites for obtaining active peroxide species. Here, we take La_0.4Sr_0.6CoO_3‑δ as a model catalyst and develop an anionic redox activity regulation method to activate lattice oxygen by tuning charge transfer between Co⁴⁺ and O^2–. Advanced XAS and XPS demonstrate that our method can effectively decrease electron density of surface oxygen sites (O^2–) to form more reactive oxygen species (O^2‑<i>x</i>), which reduces the activation energy barriers of molecular O₂ and leads to a very high CO catalytic activity. The revealing of the activation mechanism for surface oxygen sites in perovskites in this work opens up a new avenue to design efficient solid catalysts. Furthermore, we also establish a correlation between anionic redox chemistry and CO catalytic activity