Operando 3D Visualization of Migration and Degradation of a Platinum Cathode Catalyst in a Polymer Electrolyte Fuel Cell

The three‐dimensional (3D) distribution and oxidation state of a Pt cathode catalyst in a practical membrane electrode assembly (MEA) were visualized in a practical polymer electrolyte fuel cell (PEFC) under fuel‐cell operating conditions. Operando 3D computed‐tomography imaging with X‐ray absorption near edge structure (XANES) spectroscopy (CT‐XANES) clearly revealed the heterogeneous migration and degradation of Pt cathode catalyst in an MEA during accelerated degradation test (ADT) of PEFC. The degradative Pt migration proceeded over the entire cathode catalyst layer and spread to MEA depth direction into the Nafion membrane. 3D visualization of catalyst degradation: The 3D distribution and oxidation state of a Pt cathode catalyst in a practical membrane electrode assembly (MEA) were visualized under polymer electrolyte fuel cell operating conditions. Operando 3D CT‐XANES techniques clearly revealed the heterogeneous migration and degradation of the Pt cathode catalyst during accelerated degradation test cycles.