This work aims to contribute to the understanding of the degradation phenomena of carbon-supported Pt (Pt/C) catalysts in proton exchange membrane fuel cell cathodes, and two procedures are proposed for increasing their stability. The first is performed by inserting niobium pentoxide, and the second one by inserting tungsten carbide onto the carbon support. Both modified cathode materials are analyzed by physical techniques (X-ray diffraction, energy dispersive X-ray analysis, and identical location transmission electron microscopy, IL-TEM), and electrochemical tests (cyclic voltammetry and rotating disc electrode), and the results are compared with those for a commercial Pt/C electrocatalyst (Etek, wt. 20%). Accelerated aging tests are performed with a standard protocol (electrode cycling from 0.6 V to 1.0 V vs. RHE (reversible hydrogen electrode), 3 s at each potential), while the microstructure of each electrocatalyst is monitored by IL-TEM. Two phenomena leading to electrochemical surface area loss are detected: Pt particle growth and the loss of catalyst material, mainly due to the support degradation. By comparing IL-TEM profiles before and after the aging tests, it is noted that both support modifications are effective for reducing Pt nanoparticle growth. However, WC addition also increases the particles corrosion and detachment, so that Nb2O5 addition is more effective for increasing Pt/C stability. (C) 2018 Elsevier Ltd. All rights reserved.