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 complex, three-dimensional morphologies, the activity/stability balance begins to shift where an additional mechanism of performance degradation driven by the tendency to reduce the overall surface free energy of the system, results in material instability. It is critical that a more detailed fundamental understanding of the mechanisms of morphological and compositional instability and degradation in these topologically complex electrocatalytic materials be developed in order to propose strategies to improve their operational lifetime.

Here we will present an analysis of the mechanisms of material degradation for electrocatalysts with complex, three-dimensional nanoscale morphology with emphasis on operational conditions relevant for the oxygen reduction reaction (ORR). With a more fundamental understanding of the sources of structural evolution and performance metric degradation, we highlight the influence of the metal/electrolyte interface in governing both stability and activity. We will also present results of several mitigation strategies for the inherent instability of the three-dimensional morphology and their impact on electrocatalyst activity and selectivity.