Highly Efficient B-Site Exsolution Assisted by Co Doping in Lanthanum Ferrite toward High-Performance Electrocatalysts for Oxygen Evolution and Oxygen Reduction

Alloy/perovskite composites prepared by exsolution of Fe-based perovskite have attracted wide attention due to their embedded and well anchored structure, which have broad applications in heterogeneous catalysis and energy conversion. Herein, we use Co-doped lanthanum ferrite as a model to study the effect of doping on the B-site exsolution of Fe-based perovskite. CoFe alloy can be exsolved from La0.9Fe0.9Co0.1O3 (LFCO) after heat treatment at 500 degrees C in a reduced atmosphere, whereas Fe will not be exsolved from La0.9FeO3 (LFO). Density functional theory calculations revealed that the stability of LFCO decreased after Co is doped into the lanthanum ferrite perovskite lattice and the formation energy of the Co-Fe bond on the surface of LFCO is lower than that of Fe-Fe in LFO, which promises an easier exsolution of CoFe alloy than the pristine Fe cluster. In addition, owing to the strong interaction and charge transfer between the exsolved CoFe alloy and parent perovskite, as well as the longer Fe-O bond after exsolution, the exsolved composite can act as an excellent bifunctional electrocatalyst for oxygen evolution and oxygen reduction reactions. Our work not only reveals the mechanism of the alloy exsolution in Fe-based perovskites but also provides a potential route to prepare the highly efficient electrocatalysts.