Electrochemical Quantifying, Counting, and Sizing Supported Pt Nanoparticles in Real Time.

Knowledge about controlling the activity and catalyst degradation mechanisms of platinum-based catalysts has been limited by technical impediments. Here we show a facile in situ electrochemical procedure for the simultaneous assessment of the mean size and number of Pt nanoparticles (Ptnano) from an evaluation of the electrochemically surface area (ECSA) and the breakthrough in electrochemical quantification of the Pt content. The electrochemical procedure enables in situ characterization of the factors related to the catalytic activity and monitoring of the changes in Pt content during an accelerated durability test. Surprisingly, the ECSA loss was observed only from the growth of Ptnano mean size even without any Pt loss over the potential range, 0.6-1.0 V vs RHE, at room temperature. These results strongly support the long-standing debate that if the coarsening of Ptnano from crystal migration and coalescence can occur in low temperature fuel cells.