Tunable Internal and Surface Structures of the Bifunctional Oxygen Perovskite Catalysts

• Published in: Advanced energy materials Vol. 5; no. 24; pp. np - n/a
• Main Authors: Jung, Jae-Il, Park, Seungkyu, Kim, Min-Gyu, Cho, Jaephil
• Format: Journal Article
• Language: English
• Published: Weinheim Blackwell Publishing Ltd 01.12.2015; Wiley Subscription Services, Inc
• Subjects: Argon; bifunctional oxygen perovskite electrocatalysts; Catalysis; Catalysts; Defects; Heat treatment; internal and surface structures; Oxides; oxygen evolution reactions; oxygen reduction reactions; Perovskites; Surface structure
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.201501560

Perovskite oxide ceramics attracts significant attention as a strong candidate of bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalyst for the metal‐air batteries. Numerous approaches to the viability of bifunctional perovskite electrocatalyst represent that the electro­chemical performance is highly correlated with defect chemistry, surface structure, and overall polycrystalline perovskite structure. By making use of the intrinsic flexibility of internal structure and high nonstoichiometry in perovskite oxide, the heat treatment effect of the complex Ba0.5Sr0.5CoxFe1‐xO3‐δ (x = 0.2 and 0.8) perovskites in argon atmosphere at 950 °C (Ar‐BSCF5582 and Ar‐BSCF5528) on the surface structure/defect chemistry and electrocatalytic performance is intensively investigated. Upon heat‐treatment in argon atmosphere, the amorphous thickness layer increases from ≈20 to 180–200 nm in BSCF5582, while there is little change in BSCF5528 with ≈20 nm. The electrocatalytic performance of BSCF5582 catalyst both in ORR and OER deteriorates seriously, while Ar‐BSCF5528 demonstrates a significant increase of electro­chemical performance in ORR. This study demonstrates that the electrochemical performances of a perovskite catalyst can be significantly determined by the simultaneous modification of both surface structure and internal defect chemistry, which are explained with transmission electron microscopy and atomic‐selective X‐ray absorption fine structure analyses, respectively. Perovskite oxide ceramics are an attractive candidate bifunctional electrocatalyst for rechargeable metal‐air batteries. The dynamic defect chemistry and internal/structure changes when perovskite oxide ceramics are subject to the heat‐treatment in argon atmosphere are introduced, and their subsequent effect on the electrochemical performances of the bifunctional perovskite catalyst are substantially described.