Pt particles were deposited on a glassy carbon substrate using a landmark by a mask scratch-based Pt electrodeposition method to observe the same Pt particles by ex situ scanning electron microscopy before and after a potential cycling procedure. The potential cycling was conducted in a H2O2-containing 0.5 mol dm(-3) H2SO4 solution. As a result, the Pt particle degradations are clearly observed in the solution containing 100 mmol dm(-3) H2O2 in the potential range of 0.04-1.44 V vs. RHE; whereas, the degradations become more remarkable at 0.34-1.44 V vs. RHE. To clarify the reason for this potential cycling range-dependence of the Pt particle degradations, the weight change of a Pt electrode during potential cycling in the presence of H2O2 was measured using an electrochemical quartz crystal microbalance. The result suggests that the dissolved Pt is re-deposited on the Pt in ca. 0.01-0.40 V vs. RHE, which well explains the difference of the Pt particle degradations by the potential cyclings between 0.04-1.44 and 0.34-1.44 V vs. RHE. (C) 2012 Elsevier B.V. All rights reserved.