In this study, the hydrogen oxidation reaction (HOR) at the modeled three-phase interfaces of before and after degradation was investigated by combining electrochemical impedance spectroscopy (EIS) and porous microelectrode (PME) techniques. The powder mixture of a carbon-supported Pt catalyst and Nafion-packed PME (Electrode-1) was modeled as a non-degraded three-phase interface. On the other hand, the powder mixture of carbon black and Nafion-packed Pt electroplated PME (Electrode-2) modeled as a degraded three-phase interface. Electrode-1 showed a higher HOR activity than Electrode-2. Based on the EIS result, when compared to Electrode-1, both the charge transfer and mass transfer resistances of Electrode-2 significantly increased, suggesting a suppression of the HOR activity on the three-phase interface of the degraded model. That is, the charge transfer and mass transfer are hindered on the degraded three-phase interface. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.