Unveiling CeZnO_x Bimetallic Oxide: A Promising Material to Develop Composite SPPO Membranes for Enhanced Oxidative Stability and Fuel Cell Performance

Abstract

The incorporation of cerium−zinc bimetallic oxide (CeZnO x ) nanostructures in sulfonated poly(2,6-dimethyl-1,4phenylene oxide) (SPPO) membranes holds promise in an enhanced and durable fuel cell performance. This investigation delves into the durability and efficiency of SPPO membranes intercalated with CeZnO x nanostructures by varying the filler loading of 1, 2, and 3% (w/w). The successful synthesis of CeZnO x nanostructures by the alkali-aided deposition method is confirmed by wideangle X-ray diffraction spectroscopy (WAXS), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analyses. CeZnO x @SPPO nanocomposite membranes are fabricated using a solution casting method. The intricate interplay of interfacial adhesion and coupling configuration between three-dimensional CeZnO x and sulfonic moieties of the SPPO backbone yields an enhancement in the bound water content within the proton exchange membranes (PEMs). This constructs simultaneously an extensive hydrogen bonding network intertwined with the proton transport channels, thereby elevating the proton conductivity (K m ). The orchestrated reversible redox cycling involving Ce 3+ /Ce 4+ enhances the quenching of aggressive radicals, aided by Zn 2+ , promoting oxygen deficiency and Ce 3+ concentration. This synergistic efficacy ultimately translates into composite PEMs characterized by a mere 4% mass loss and a nominal 6% decrease in K m after rigorous exposure to Fenton's solution. Remarkably, an improved power density of 403.2 mW/cm 2 and a maximum current density of 1260.6 mA/cm 2 were achieved with 2% loading of CeZnO x (SPZ-2) at 75 °C and 100% RH. The fuel cell performance of SPZ-2 is 74% higher than its corresponding pristine SPPO membrane.