In situ construction of ultra-thin PANI/CeOx layer on proton exchange membrane for enhanced oxidation resistance in PEMFC

Free radical degradation of proton exchange membranes (PEMs) under in situ conditions commonly leads to performance losses in proton exchange membrane fuel cells (PEMFCs). Blending or doping with antioxidative additives in the polymer matrix has been widely exploited to mitigate oxidative degradation. However, this approach commonly has additional challenges, including reductions in proton conductivity and diffusion loss of antioxidative additives, leading to the overall loss of fuel cell performance. Herein, we develop an alternative strategy of in situ growth of thin porous polyaniline (PANI) film on the proton conductive sulfonated poly (biphenyl indole) membrane (SBPIM), encapsulating free radical scavenger (ceria oxide, CeOx) inside. The porous PANI film functions as a scaffold to suppress agglomeration or diffusion loss of CeOx. Ex situ Fenton's reagent and in situ durability tests demonstrate that this PANI/CeOx thin layer significantly prevents free radical attack on the PEM without sacrificing fuel cell performance. A H2/O2 PEMFC test exhibits a promising peak power density (988 mW cm−2 at 80 °C with 100 % RH) and at least 400 h open circuit voltage (OCV) durability.