Fig. 1: Perovskite structure and characterization of fresh samples.

a Unit cell of perovskite oxide (ABO3) with an ideal cubic structure (left) and corresponding coordination state of bulk (middle) and surface (right) lattice oxygen (perovskite surface terminated with Fe cations). EDS maps of b La1.03FeO3, c LaFeO3, and d La0.97FeO3, and corresponding HRTEM images of e La1.03FeO3, f LaFeO3, and g La0.97FeO3. h H2-TPR profiles of LaxFeO3 (x = 1.03, 1, and 0.97) oxides.