Heterogeneous electrocatalysts for the oxygen evolution reaction (OER) are complicated materials with dynamic structures. They often exhibit potential-induced phase transitions, potential-dependent electronic properties, variable oxidation and protonation states, and disordered local/surface phases. These properties make understanding the OER, and ultimately designing higher-efficiency catalysts, challenging. I will discuss techniques that we have adopted or developed to address the above challenges. Simple laboratory techniques include the assessment and minimization of electrolyte impurities, the use of a quartz crystal microbalance to monitor film loading and dissolution, and the use of in situ conductivity measurements to understand the flow of electrons from the catalyst active sites to the conductive support electrode. Measurements of intrinsic activity show that the most-active phases for OER under alkaline conditions are Fe-containing mixed-metal oxyhydroxides, as well as reveal a new OER activity trend for the first-row transition metals. Operando electrochemical atomic force microscopy shows that these oxyhydroxide structures are highly dynamic under OER conditions. Operando x-ray absorption measurements support the hypothesis of Fe-based OER active sites. Ongoing work and remaining challenges will be discussed in conclusion.

Oxygen evolution reaction electrocatalysis on mixed-metal oxyhydroxides

2019 Fall National Meeting

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