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

Abstract

Abstract: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 the 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 500-1,000 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 (ORR) where high positive potentials are typically employed.

Pt-Richcore/Sn-Richsubsurface/Ptskin Nanocubes As Highly Active and Stable Electrocatalysts for the Ethanol Oxidation Reaction

“…It is generally accepted that for bimetallic Pt-based catalysts, the onset of EOR usually takes place at electrode potentials where the less noble metal is leached from the surface of the bimetallic alloy. In addition, it has been previously shown that potential cycling, especially to high potentials, can give rise to severe changes in the surface structure of shape-controlled Pt nanocatalysts 44 . For those reasons, the chemical microstructural stability and durability of the Pt-Sn cubes were evaluated by STEM imaging and EELS elemental mapping after potential cycling.…”

Testing fuel cell catalysts under more realistic reaction conditions: accelerated stress tests in a gas diffusion electrode setup

“…The electrode potential can be controlled independently of the reaction conditions allowing not only comparison of the performance of different PEMFC catalysts, but also investigation into how potential excursions affect the catalyst stability and the degradation mechanism. For the latter, accelerated degradation tests (ADTs) are employed in combination with techniques such as identical location transmission and scanning electron microscopy (IL-TEM and IL-SEM) [3][4][5][6][7][8][9][10][11][12], and scanning flow cells (SFC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS) [13,14]. Thus, degradation mechanisms, such as metal dissolution and particle detachment, can be related to certain excursions in the electrode potential, as well as catalyst properties such as particle size and carbon support.…”

Synthesis of a Small Amorphous PdMo/C Nanocatalyst and Pd Nanocubes Enclosed within (100) Planes and Their Use for Ethylene Glycol Electro–oxidation

“…This behavior can be attributed to the catalyst's weak adsorption of both OH − and by‐products to regenerate the active sites. Moreover, it is known that electrochemical cycling can damage the particle shape, but as we have previously observed, [10c, 27] the nanocatalysts maintain the presence of {100} terraces despite losing their shape, thereby preserving their activity. Thus, the Pd/C nanocubes maintained their high activity after 400 cycles because the (200) planes were preserved.…”