Influence of metal cleaning on the particle size and surface morphology ofplatinum black studied by NMR, TEM and CV techniques

Cyclic voltammetry (CV), transmission electron microscopy (TEM) and C-13 nu clear magnetic resonance spectroscopy (NMR) were employed to investigate th e particle size and surface morphology of fuel cell grade platinum black sa mples as received and prepared under three different cleaning methods. The Pt particle growth was most markedly caused by extensive CV treatment moder ately by cleaning with chromic acid, and negligibly by holding the potentia l at 250 mV. Even single anodic sweep CV removed Pt adatoms; in contrast, c leaning with chromic acid and holding the potential at 250 mV did not. Our results demonstrate that a cleaning method should be chosen with the knowle dge of its effect on the metal surface and particle size. The possibility o f detecting the particle size change due to cleaning procedures by C-13 NMR is also discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.