Evaluating Pt Nanoparticle Electrocatalyst Stability on Corrosion Free Carbon Supports Using Identical Location TEM

Probing platinum (Pt) nanoparticle (NP) stability, free from convolution with corrosion of the underlying carbon support, under the start-stop conditions of a proton exchange membrane fuel cell, is challenging. To address this problem with a focus on tracking NP morphology changes, we use identical-location transmission electron microscopy, in combination with corrosion-resistant, electron-transparent, boron-doped diamond electrodes. Automated image analysis is developed to enable faster and easier processing. Information concerning NP area, positional changes, and relationship to nearest neighbor distance is extracted on an NP-by-NP basis by tracking the same NPs, pre- and post-accelerated stress testing in perchloric acid under conditions which promote carbon corrosion for sp² carbons. Measurements are made in several locations with ca. 200 NPs analyzed per image. A significant fraction of the NPs, 40%-50%, are found to be area stable, with only a small number growing and the remaining decreasing very slightly in area (less than a single atom layer) due to transient dissolution. The average distance of travel of an NP after accelerated stress testing is ∼0.36 nm (n = 545). This data highlights both the stability of the Pt-BDD interaction and the potential for BDD use as an electrocatalyst support, under high anodic potentials.