Ceria Stabilized by Titanium Carbide as a Sustainable Filler in the Nafion Matrix Improves the Mechanical Integrity, Electrochemical Durability, and Hydrogen Impermeability of Proton-Exchange Membrane Fuel Cells: Effects of the Filler Content.

Cerium oxide-anchored titanium carbide (CeO2-TiC) is realized as a potential inorganic filler when modifying the Nafion matrix of a proton-exchange membrane fuel cell (PEMFC). A hydrothermal strategy was employed to synthesize CeO2-TiC of high crystallinity as a filler to mitigate the problematic properties of a proton-exchange membrane (PEM). CeO2-TiC with a weight ratio of 0.5, 1, 1.5, or 2% was incorporated into a Nafion matrix to form a hybrid by adopting a solution-casting procedure. Reinforcement owing to the presence of TiC provides increased tensile strength to PEM, and the addition of CeO2 improves the durability of PEM by scavenging free radicals. The microstructural, thermomechanical, physiochemical, and electrochemical properties of PEM, including contact angle, water sorption, water uptake, and proton conductivity, were extensively studied. Random dispersion of CeO2-TiC in the Nafion matrix improves the thermal stability, tensile strength, and water uptake while retaining proton conductivity, as compared with those of pristine Nafion. As a result, optimized Nafion/CeO2-TiC (1 wt %) achieved undiminished PEMFC performance compared to that of pristine Nafion while operating the device at 60 °C and 100% relative humidity. In addition, Nafion/CeO2-TiC (1 wt %) experienced the degradation of merely 0.6 mV h-1 during 200 h operation under identical conditions. Compared to that of Nafion/CeO2-TiC (1 wt %), pristine Nafion and Nafion-212 displayed accelerated and comparable degradation (for pristine Nafion, 1.3 mV h-1; for Nafion-212, 0.4 mV h-1). PEMFC power output, hydrogen permeability, and morphology of samples were examined after the durability test; the results indicate that Nafion/CeO2-TiC (1 wt %) is extremely stable. Since various Nafion hybrids have been reported as highly durable PEMs, this study is expected to open up new perspectives to expanding their applications, especially in sustainable PEMFC technology.