Heteropolyacids (HPAs) were adsorbed onto high surface area carbon, and incorporated in polymer electrolyte membrane fuel cells (PEMFCs) between the electrodes and membrane, forming "sub-layers." The addition of HPAs to these sub-layers significantly decreased membrane degradation in cells subjected to accelerated stress tests, as evidenced by a 50% reduction in fluoride emission rate (FER) and open circuit voltage (OCV) decay. Evidence of increased HPA and platinum concentration within the sub-layer indicates substantial HPA mobility. Modeling of the voltage profile through the sub-layer and membrane indicated that platinum precipitation was possible within the sub-layer, and that this is dependent on both the reduction potential and concentration of the HPA. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.017302jes] All rights reserved.