Identical Location Scanning Electron Microscopy: A Case Study of Electrochemical Degradation of PtNi Nanoparticles Using a New Nondestructive Method

The electrochemical degradation of PtNi and PtCu alloy nanoparticles is studied with a new, nondestructive variant of scanning electron microscopy (SEM). The method allows for observation of the same site (same nanoparticle) before and after electrochemical treatment, hence the name identical location SEM, IL-SEM. The method was complemented with other techniques such as energy-dispersive X-ray spectroscopy (EDS) and electrochemical thin film rotating disk electrode (TF-RDE) measurements. During initial potential cycling, the combined results show Ni or Cu dissolution and an increase in the electrochemical surface area (ESA). After accelerated degradation test (ADT), however, morphological changes (visible roughening) of the catalyst surface and a decrease in oxygen reduction reaction (ORR) specific activity are observed. In contrast to transmission electron microscopy (TEM and IL-TEM), the major advantage of SEM and IL-SEM is the ability to study surface phenomena rather than the bulk characteristic of a nano-object.