While fast screening techniques (e.g. Fenton's tests) are commonly used to predict the ability of antioxidants to function as free radical scavengers [2,9], there are presently no screening methods for evaluating how stable these additives will be in the PEMFC environment. Thus, the stability of any potential new antioxidant materials must be evaluated in-situ, with full cathode or anode accelerated stress tests (ASTs) being performed [8]. Unfortunately this can be both time consuming and expensive, and is therefore a bottle-neck in the development and understanding of new antioxidants. Ideally, any ex-situ stability test for antioxidant materials would provide information not just on chemical stability, but also on the relative ratios of cations (e.g. Ce3þ/Ce4þ) that are released, as this ratio may impact the efficiency of the free radical scavenging of these additives [4].