P-076

Ana Rebeka Kamšek

ana.rebeka.kamsek@ki.si

Francisco Ruiz-Zepeda, Jan Vidergar, Anja Logar, Goran Dražić, Nejc Hodnik

National Institute of Chemistry, Slovenia

Quantifying catalyst degradation with identical-location microscopy

Commonly used electrocatalysts for the oxygen reduction reaction in proton exchange membrane fuel cells consist of platinum-based nanoparticles that are dispersed over a carbon support with a high surface area. By partially substituting the platinum with a more abundant and cost-effective transition metal, we can create Pt-alloy nanoparticles with an improved performance. Despite advancements in platinum utilization, intrinsic activity, and overall costs, the primary challenge for Pt-M electrocatalysts remains their long-term durability.

The catalytic properties of electrocatalysts are determined by their structural features. In practical applications, batches of these advanced functional materials consist of a vast number of nanoparticles, each displaying a wide range of differences at the atomic scale, including variations in size, shape, composition, and crystal structure. In addition to this inherent complexity, the structure of the electrocatalyst can change during operation due to degradation mechanisms.

To accurately track structural changes, it is essential to collect data during a reaction instead of relying solely on still images of selected sample regions. Given the diversity of nanoparticle structures, understanding their local history provides more insight than top-down techniques. Identical-location scanning transmission electron microscopy (IL-STEM) addresses this by imaging the same site before and after electrochemically induced changes, allowing for reliable conclusions about structural, morphological, and compositional differences. This method is particularly valuable for studying structure-stability relationships.

Understanding individual degradation mechanisms under relevant industrial conditions is crucial for developing durable materials. This study analyzes IL-STEM images of a Pt-Co/C electrocatalyst to track degradation mechanisms. While previous studies relied on manual analysis of limited data, we employed detailed image analysis to quantify the frequency of individual degradation mechanisms and their relationship with nanoparticles of specific sizes and shapes. Our approach demonstrates that IL-STEM images provide valuable, quantifiable insights into electrocatalyst stability and its catalytic properties.