Structural Changes of Cobalt-Based Perovskites upon Water Oxidation Investigated by EXAFS

• Published in: Journal of physical chemistry. C Vol. 117; no. 17; pp. 8628 - 8635
• Main Authors: Risch, Marcel, Grimaud, Alexis, May, Kevin J, Stoerzinger, Kelsey A, Chen, Tina J, Mansour, Azzam N, Shao-Horn, Yang
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 02.05.2013
• Subjects: Condensed matter: structure, mechanical and thermal properties; Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder; Cross-disciplinary physics: materials science; rheology; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Materials science; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Local structure; Phase transformations; Crystal-phase transformations; Oxidation; X-ray absorption; Cobalt; EXAFS; Crystal structure
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp3126768

While many perovskites remain crystalline during the oxygen evolution reaction (OER) in alkaline media, some highly active perovskites become amorphous. We studied the local structure changes of perovskites LaCoO3, Ba0.5Sr0.5Co0.8Fe0.2O3‑δ, and SrCo0.8Fe0.2O3‑δ before and after OER by X-ray absorption spectroscopy. No change in either local structure or OER activity was observed for LaCoO3, while considerably enhanced OER activities and the conversion of the local structure from corner-sharing octahedra to edge-sharing octahedra were noted for Ba0.5Sr0.5Co0.8Fe0.2O3‑δ and SrCo0.8Fe0.2O3‑δ as a result of the OER. Possible processes responsible for the structural change and enhanced OER activities are discussed.