Ionomer-free ultrathin electrodes, such as the 3M Nanostructured Thin Film (NSTF) electrode, provide a plausible pathway to reduce Pt cost in low temperature fuel cells. Long-term durability testing of the NSTF electrode was performed using test protocols designed to simulate fuel cell operational situations which may be found in real applications. The excellent stability of NSTF catalyst allowed probing of new degradation aspects that would normally be convoluted with other catalyst degradation mechanisms, such as carbon corrosion and Pt dissolution, if a conventional dispersed catalyst was used. It was hypothesized that H2O2 produced as a by-product of oxygen reduction reaction induced ionomer degradation especially in the area close to the cathode electrode. Correlation among different events that contribute to the degradation was discussed, prompting the necessity to minimize the reversible degradation in order to prevent premature electrode failure. Mitigation strategies to maximize the electrode life were also suggested. (C) 2014 The Electrochemical Society. All rights reserved.