Irreversible Structural Dynamics in Bimetallic Pt-Ni Alloy Catalyst Under Alternating Redox Environments

Abstract

The better understanding on the structural dynamics of a bimetallic catalyst during its interaction with reactive environments is a prerequisite for the development of an efficient catalyst for proton exchange membrane fuel cells (PEMFCs). The main focus should be given to the outermost layers of catalytically active material which are directly involved in catalysis.Herein, we applied the synchrotron radiation photoelectron spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS) techniques to investigate surface chemistry aspects in a PtNi alloy catalyst under alternating oxidation (O2) and reduction (H2) atmospheres at different temperatures that simulate its behavior as a cathode catalyst in PEMFCs. The experimental results are substantiated by theoretical calculations on model PtNi nanoalloys.We showed that PtNi alloy does not maintain its chemical integrity and undergoes surface reconstruction during the switching between oxidizing and reducing conditions in terms of relative surface nickel enrichment. Along with compositional changes catalyst coarsening was observed by atomic force microscopy (AFM).The revealed behavior of the PtNi alloy provides valuable fundamental insights that help to gain advanced understanding of PtNi alloy catalytic activity in real conditions. Figure 1