Part 2: Quantitative Electrochemical Liquid Cell TEM Studies of Catalyst Degradation Mechanisms

Dr. Sungin Kim | Postdoc (Yang Group) Cornell University
In this study, we present advanced electrochemical liquid-cell TEM (e-LCTEM) techniques tailored for tracking Pt/C degradation under electrochemical polarization at short intervals with high spatial resolution. Our innovative approach combines microfabrication-based sample preparation with in situ control of electrolyte thickness, ensuring reliable electrochemical signal acquisition and direct observation of sequential catalyst degradation. Quantitative imaging analyses conducted at both global areas and single-particle levels unveil a distinctive degradation mechanism primarily driven by nanoparticle migrations. Smaller nanoparticles exhibit a higher susceptibility to migration, leading to coalescence or detachment. In particular, our method enables us to capture the degradation process of coalesced particles that maintain the mobility and lead to subsequent migration and detachment, despite their enlarged sizes. This migration-gated degradation mechanism provides a new perspective on the size-dependent durability of supported nanoparticles, complementing the prevailing explanation centered on the size-dependent dissolution kinetics of nanoparticles. In addition, we will introduce the latest development of operando heating/cooling electrochemical liquid-cell STEM (EC-STEM) at Cornell.