Limitations of identical location SEM as a method of degradation studies on surfactant capped nanoparticle electrocatalysts.

• Pre-electrolysis imaging in IL-SEM can locally inactivate the catalyst surface. • Passivation occurs due to the under-beam formation of a carbonaceous crust. • The carbonaceous crust is formed by the irradiation of capping agent remnants. • Different degradation patterns are observed on pre-scanned and pristine areas. Identical location scanning electron microscopy (IL–SEM) has become an important tool for electrocatalysis research in the past few years. The method allows for the observation of the same site of an electrode, often down to the same nanoparticle, before and after electrochemical treatment. It is presumed that by IL–SEM, alterations in the surface morphology (the growth, shrinkage, or the disappearance of nanosized features) can be detected, and the thus visualized degradation can be linked to changes of the catalytic performance, observed during prolonged electrolyses. In the rare cases where no degradation is seen, IL–SEM may provide comfort that the studied catalyst is ready for up-scaling and can be moved towards industrial applications. However, although it is usually considered a non-invasive technique, the interpretation of IL–SEM measurements may get more complicated. When, for example, IL–SEM is used to study the degradation of surfactant-capped Ag nanocubes employed as electrocatalysts of CO 2 electroreduction, nanoparticles subjected to the electron beam during pre-electrolysis imaging may lose some of their catalytic activity due to the under-beam formation of a passive organic contamination layer. Although the entirety of the catalyst obviously degrades, the spot mapped by IL–SEM reflects no or little changes during electrolysis. The aim of this paper is to shed light on an important limitation of IL–SEM: extreme care is necessary when applying this method for catalyst degradation studies, especially in case of nanoparticles with surface-adsorbed capping agents. [ABSTRACT FROM AUTHOR]