We present the results of electrochemical analysis and in-situ Raman spectroscopy of iron perovskites during oxygen reactions in alkaline solutions. We show that iron perovskites, Sr2-xCaxFe2O6-δ, with tuned oxygen vacancy content and ordering are a promising class of materials as catalysts for oxygen evolution reaction (OER), a key component of water electrolysis. We use solid state synthesis to control the structural ordering and the content of oxygen vacancy. We show that electrochemical activity correlates with δ, and compounds with δ→1 tend to show higher activity. However, the effect of oxygen deficiency and vacancy ordering in the perovskite-based oxide electrocatalysis and especially mechanism behind oxygen intercalation and surface amorphization during OER remain poorly understood. We use steady state electrochemical analysis to show that a subset of these compounds undergo oxygen intercalation before the onset of OER. Interestingly, the amount and energetics of intercalation is a function of A and B site composition. Some of the compounds doped at the B-site (with Mn and Co) show structural evolution and intercalation during OER. Raman analysis also shows interesting synergistic effects, where second order scattering is observed in some of the highly disordered structures. We will use these analyses to provide further insight into the interplay of structural evolution and catalysis in this class of compounds.

Structural evolutions in iron perovskites during oxygen evolution electrocatalysis

2019 Fall National Meeting

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