For the commercialization of polymer electrolyte membrane fuel cells (PEMFCs), it is essential to achieve high performance while improving the durability of the membrane electrode assembly. In particular, the durability of PEMFCs can be improved by adding radical scavengers, such as CeO2 (ceria), to the membrane. Though it is desirable to insert the ceria at the interface between the membrane and electrode, where the generated radical attack initiates, this increases interfacial resistance and ionic resistance, thereby inducing a probable reduction in initial performance, compared to that of a conventional membrane. Here, we developed modified Nafion electrolyte membranes with a spatially located patterned ceria containing Nafion ionomer to improve durability while minimizing performance degradation. The fabrication process includes an etching process to pattern the electrolyte membrane, and the ceria nanoparticle layer is selectively deposited by spray coating onto the membrane. The synergetic effect of the structural modification of the electrolyte membranes and the introduction of the functional ceria layer exhibited improved chemical durability, while maintaining the initial performance of the PEMFC.

Structural color refers to a phenomenon, in which white light is influenced by the structure and the color is expressed. It can express various colors depending on the structures and has an advantage in terms of durability compared to the conventional dyeing processes. However, the structural color from a single layer easily varies depending on the light irradiation angle or measurement angle. Hence, numerous studies have been conducted to improve the angle-independency of structural color by fabricating multi-layers with complex nano-patterns. But, they usually require highly controlled processing environments and are not suitable for large-area manufacturing. Therefore, this study aims to develop a fabrication process by utilizing ultra-precision machining and silicon molding. Here, angle-independent structural colors were implemented with multi-layer micro-patterned films. Through the experiments, angle-independency was evaluated by varying the number of silicon films and measurement angles. RGB and HSV values were extracted from the images and applied for quantitative analysis. The suggested fabrication process successfully exhibited the angle-independent structural color with given patterns and film thickness. It is expected that this study can contribute to improving the multi-layer fabrication processes concerning machinability and large-area production.