Lab-Scale Operando X-ray Diffraction Reveals Temperature-Accelerated Coalescence-Driven Growth of Pt Nanoparticles

Electrocatalysts are key materials for renewable energy technologies such as fuel cells, water and carbon dioxide electrolysis, and electrosynthesis. Each year, numerous highly active electrocatalysts are reported, but few reach industrial application, most commonly due to insufficient long-term stability. In this work, we develop a lab-scale operando X-ray diffraction (XRD) technique with the unique capability of simultaneously recording high-quality electrochemical data and XRD patterns under industrially relevant reaction conditions. Using this technique, we investigate the degradation of a high metal-loading (60 wt % Pt) Pt/C catalyst at elevated operating temperatures. At 28 °C, the pristine Pt particles with the volume-weighted mean size of 4.9 ± 0.2 nm grow nearly linearly to 5.5 ± 0.1 nm after a series of potential cycling tests. In comparison, at 70 °C, the growth process is significantly accelerated, with the final particle size reaching 7.9 ± 0.1 nm, yet the growth pattern remains linear across different testing conditions, mirroring the trend observed in the simultaneously recorded electrochemical results. Post-mortem analysis by transmission electron microscopy further reveals morphological changes, which, together with the operando XRD results, suggest that particle migration and coalescence are likely important contributors to the observed particle growth. We expect this lab-scale operando XRD technique to enable systematic and accessible investigations of electrocatalyst stability across a wide range of reactions under realistic operating conditions.