Size and composition dynamics of nanoparticle electrocatalysts

The durability of the electrocatalysts in polymer electrolyte membrane fuel cells (PEMFCs) is one of the factors limiting use of this technology. To improve durability, the macroscopic durability (e.g., loss of catalyst surface area) must be understood in microscopic terms: we need to better understand the nanoparticle electrocatalyst structural dynamics at an atomic scale and in real time during electrochemical stressing. In this talk, I describe in-situ X-ray scattering experiments on Pt and CuPt alloy nanoparticle electrocatalysts under conditions that mimic the degradation environment in operating fuel cells (electrode potential cycles and holds). This enables us to monitor, in real time, the atomic scale structure of the electrocatalysts such as particle size, lattice constant and extent of crystallinity.