Revealing compositional evolution of PdAu electrocatalyst by atom probe tomography

TL;DR

This study uses atom probe tomography to reveal atomic-scale chemical changes in PdAu electrocatalysts after degradation, showing leaching of Pd and B and formation of Au-rich surface regions, which impact catalyst performance.

Contribution

It introduces atom probe tomography as a novel method to analyze microstructural and chemical evolution in PdAu catalysts after degradation testing.

Findings

Pd and B are leached from nanoparticles

Au-rich regions form at the catalyst surface

No morphological changes observed after 1000 MOR cycles

Abstract

Pd-based electro-catalysts are a key component to improve the methanol oxidation reaction (MOR) kinetics from alcohol fuel cells. However, the performance of such catalysts is degraded over time. To understand the microstructural/atomic scale chemical changes responsible for such effect, scanning (transmission) electron microscopies and atom probe tomography (APT) were performed after accelerated degradation tests (ADT). No morphological changes are observed after 1000 MOR cycles. Contrastingly, (1) Pd and B are leached from PdAu nanoparticles and (2) Au-rich regions are formed at the surface of the catalyst. These insights highlight the importance of understanding the chemical modification undergoing upon MOR to design superior catalysts.