Accelerated Stress Tests of Pt/HSAC Electrocatalysts: an Identical-Location Transmission Electron Microscopy Study on the Influence of Intermediate Characterizations

摘要

The influence of intermediate characterizations used in long-term accelerated stress tests (ASTs) to monitor the changes of the electrochemically active surface area of carbon-supported Pt nanoparticles (Pt/HSAC) was investigated. Our results indicate that, in the studied experimental protocol (potentiostatic polarization at E = 1.0 V vs. RHE during 96 h), the loss of the electrochemically active surface area is greatly exacerbated by intermediate characterizations such as cyclic voltammetry or stripping of a saturated CO_(ad) surface layer. These results can be understood in view of the breakdown of the passivation layer formed on the Pt/HSAC electrocatalyst during the polarization at is E= 1.0 V vs. RHE. By using identical location transmission electron microscopy, the structural modifications of the Pt/HSAC nanoparticles could be monitored. The migration/agglomeration of Pt nanocrystallites, the growth of Pt nanocrystallites by electrochemical OstWald ripening, and the corrosion of the high surface area carbon support are more pronounced when cyclic or CO_(ad) stripping voltammograms are implemented in the AST. A detailed analysis of the identical-location transmission electron microscopy images also indicates that adsorbed CO molecules minor the dissolution of Pt~(2+) ions into the electrolyte.