Exsolution manipulated local surface cobalt/iron alloying and dealloying conversion in La0·95Fe0·8Co0·2O3 perovskite for oxygen evolution reaction

Abstract

The preparation of metal/perovskite oxide composite by exsolution is an effective way to synthesize highly efficient electrocatalysts. For transition metal doped Fe-based perovskite oxides, the exsolved metal nanoparticles are usually Fe-based alloys. Herein, we in-situ exsolved single Co metal from A-site defective La0·95Fe0·8Co0·2O3 (LFCO) via a thermal reduction method above 600 °C. At lower temperature (500 °C), the species exsolved from LFCO is CoFe alloy, while the temperature rises above 600 °C, the composition of metal nanoparticles changes to single Co metal by cation exchange between Fe in metal nanoparticles and Co in perovskite oxide, forming Co/LFCO composite. This phenomenon could be owing to the higher co-segregation energy of Co than Fe cations, and LaFeO3 is thermodynamically more stable at high temperatures. As a result, Co/LFCO shows largely improved conductivity than CoFe/LFCO counterpart, and thereof enhanced activity for oxygen evolution reaction (OER). Our work has positive implication for designing a wide range of efficient electrocatalysts by in-situ tuning the composition of surface nanoparticles.