Oxidation and Surface Segregation Behavior of a Pt–Pd–Rh Alloy Catalyst

Abstract

Platinum gauze catalysts are used extensively in the production of nitric acid from ammonia, where they are subject to harsh operating conditions combining elevated temperatures and oxidizing environments. These cause significant loss of metal species as volatile oxides. How different metallic species behave in these environments at a fundamental, atomic-scale level is not well understood. In this work, we study the early stages of oxidation of a Pt–Rh–Pd gauze at temperatures of 873–1273 K. Using a combination of advanced experimental methods, we explore how the oxidation behavior can strongly influence the surface and near-surface gauze microstructure. We show that Rh and Pd can segregate on different areas of the same surface and discuss how such atomic migration can be linked to mechanisms of metal loss from such alloys.