Scavenging of Hydroxyl Radicals by Ceria Nanoparticles: Effect of Particle Size and Concentration

The most commonly used proton exchange membranes (PEMs) for hydrogen and direct methanol fuel cells are the perfluorosulfonic acid ionomers (PFSA) such as Nafion, which are based on a Teflon-like backbone with side chains containing sulfonic groups. These materials exhibit good mechanical, chemical, and thermal stability in both oxidative and reductive media; however, the fuel cell is a reactor with strong oxidizing power, capable of reducing the durability of the PEMs. The centrality of hydroxyl radicals, HO·, in the degradation mechanism of PFSA is well documented in numerous papers, including our work. Therefore, membrane durability remains a critical issue for further development of fuel cell applications. We present the use of ceria nanoparticles (NPs) for mitigating the chemical degradation process and describe their effectiveness for scavenging hydroxyl radicals as a function of their size and concentrations. The hydroxyl radicals were generated by UV-irradiation of hydrogen peroxide, and the radic...