Identical Location Transmission Electron Microscopy Imaging of Site-Selective Pt Nanocatalysts: Electrochemical Activation and Surface Disordering

We have employed identical location transmission electron microscopy (IL-TEM) to study changes in the shape and morphology of faceted Pt nanoparticles as a result of electrochemical cycling; a procedure typically employed for activating platinum surfaces. We find that the shape and morphology of the as-prepared hexagonal nanoparticles are rapidly degraded as a result of potential cycling up to +1.3 V. As few as 25 potential cycles are sufficient to cause significant degradation, and after about 500–1000 cycles the particles are dramatically degraded. We also see clear evidence of particle migration during potential cycling. These finding suggest that great care must be exercised in the use and study of shaped Pt nanoparticles (and related systems) as electrocatlysts, especially for the oxygen reduction reaction where high positive potentials are typically employed.

This work was carried out under financial support of MICINN (project no. CTQ2013-44083-P) and the energy materials center at Cornell (emc2) an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Basic Energy Sciences, under award no. DESC0001086. R.M.A.-A. thanks the funding received from MICINN (EEBB-I-13-06184) to carry out a predoctoral stay in a foreign R&D center. This work and made use of TEM facilities of the Cornell Center of Materials Research, an National Science Foundation Materials Research Science and Engineering Center, under award no. DMR-1120296.