Phase transition of SrCo0.9Fe0.1O3 electrocatalysts and their effects on oxygen evolution reaction

Abstract Complex metal oxide has emerged as an important class of electrocatalyst for oxygen evolution reaction (OER) because of its flexibility in the crystal phase and relative ease in the control of defect structures. While different crystalline phases and solid structures may be produced from the same reactant precursors, their phase transitions and OER performances are not well understood. In this work, we present the preparation of different phases of SrCo 0.9 Fe 0.1 O 3‐δ (nominal ratio) solids using a sol–gel method and the structure–catalytic property relationship of both crystalline and amorphous structures formed at different temperatures. We observed as synthetic temperature increased, phase and composition transitions occurred from the amorphous phase to strontium carbonate and cobalt oxide, to oxygen‐deficient perovskite, and finally to perovskite. The OER activity depended highly on crystal structures. The oxygen‐deficient perovskite prepared at 750°C exhibited the highest catalytic activity, while the perovskite showed the lowest activity. X‐ray photoelectron spectroscopy analysis reveals the change of oxidation state occurred during the phase transition. This work provides a useful guideline for the design of OER electrocatalysts through controlling the crystal structures and defects in complex metal oxides, such as perovskite.