(419c) Electrochemical Coarsening in Morphologically Complex Electrocatalysts

The boundaries of functional materials development are continually being pushed where length scales down to the order of nanometers have introduced multi-functionality into the next generation of materials. The complex morphologies and compositional gradients that define these nanomaterials open pathways to new modes of instability, requiring strategies to address these instabilities and prolong the operational lifetime of these materials in real-world devices. For electrocatalytic materials possessing complex compositional profiles, three-dimensional morphologies, or unique atomic scale surface architectures, or some combination of all three, the activity/stability balance begins to shift where active materials are not stable and stable materials are not active. It is critical that a more detailed fundamental understanding of the mechanisms of morphological and compositional instability and degradation in these complex electrocatalytic materials be developed in order to propose strategies to improve their operational lifetime.

Here we will present an analysis of an additional mechanism of material degradation that comes into play for electrocatalysts with complex, three-dimensional nanoscale morphology, namely electrochemical coarsening. We will focus on the evolution of Pt alloy, open framework nanocatalysts at oxygen reduction reaction (ORR) relevant operational conditions. With a more fundamental understanding of the sources of structural evolution and performance metric degradation, we will show our development of mitigation strategies that limit the degree of electrochemical coarsening with minimal impact on electrocatalyst activity, optimizing the balance between activity and stability.