Perovskites are a family of complex oxides with the nominal formula AMO3, where A is lathanide or alkali earth and M is typically a transition metal. Perovskites displaying interesting ferroelectric, magnetic, optical, or superconducting properties have made them the subject of intense research over the past 30 years. They are of great interest as replacements for precious metals and oxides used in the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Perovskite electrocatalysts have been shown to have greater specific activities than precious metals and their oxides, but high mass activities have not yet been realized due to the complex nature of perovskite oxide surfaces and inadequate synthesis techniques which often result in unwanted phase impurities and micron-scale materials. We demonstrate the precise control over the chemical composition and structure of a series of perovskite electrocatalysts that are highly active for both the OER and ORR, key reactions for aqueous metal-air batteries (such as Zn-air) and other energy conversion systems. Each perovskite’s ability to catalyze the OER and ORR is examined using electrochemical methods. The reaction pathways are perturbed by the direct modification of the perovskite structure by selective cation replacement and via perovksite-carbon support-interactions. We examine these results in the context of structure, electronic configuration and catalytic pathways. Electroanalytical techniques such as rotating disk electrochemistry and cyclic voltammetry are used in conjunction with materials characterization enabled by dynamic light scattering, electron microscopy, nitrogen sorption, X-ray photoelectron spectroscopy and X-ray diffraction. It is demonstrated that these highly active perovskite catalysts are an emerging replacement for the precious metal catalysts.

Tuning the electrocatalytic activity of perovskite oxides for water oxidation and oxygen reduction by active site variation

253rd National Meeting (2017)

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