Polyphenol synergistic cerium oxide surface engineering constructed core-shell nanostructures as antioxidants for durable and high-performance proton exchange membrane fuel cells

The chemical degradation of proton exchange membranes (PEMs) suffering from radical attack is a crucial issue in the development of proton exchange membrane fuel cells (PEMFCs), while incorporating cerium oxide (CeO 2 ) nanoparticles (NPs) with regenerative redox properties to eliminate radicals could effectively alleviate degradation. However, the low stability and restricted activity of CeO 2 in the PEMFC operating condition and the poor compatibility with PEM due to CeO 2 agglomeration stimulate the urgency for structural modulation of CeO 2 . Achieving a balance of membrane performance and oxidation resistance through a rational surface modification strategy of CeO 2 is important for expanding PEMFC applications. Herein, polyphenols surface functionalized CeO 2 core-shell structure (CeO 2 @TP) were constructed via assembling oxidation-induced coupling tea polyphenols (TP) on CeO 2 NPs. The TP oligomeric shell as a protective layer enhances the stability of CeO 2 , mitigating radical scavenging activity degradation and improving compatibility with PEMs. Physicochemical characterisation shows that the overall performance of the nanocomposite membrane is improved due to the interaction of CeO 2 @TP nanoparticles with the polymer matrix. Gratifyingly, the phenolic hydroxyl-rich reductive TP oligomeric shell accelerates the regeneration of Ce(IV) to Ce(III), increasing the proportion of Ce(III) and oxygen vacancies on the CeO 2 surface, thus boosting antioxidation efficiency. As a result, the CeO 2 @TP-based PEMs exhibited an OCV decay rate of 0.22 mV h −1 , a maximum power density of 1.06 W cm −2 , an H 2 crossover value of 2.18 mA cm −2 , thickness retention (91.1%), and negligible Ce migration after 404 h of accelerated degradation testing. It is proven that the desired consequences of doping antioxidants in PFSA matrix can be intensified by surface modulation of the physicochemical properties of CeO 2 .