Effect ofSolid Content and Ionomer-to-Carbon Ratioon High-Solid-Content Ink-Cast Catalyst Layers for PEM Fuel Cells

The multiscale structure of the catalyst layer (CL) is fabricated through the catalyst ink dispersion, coating process, and subsequent drying process. The formulation parameters of the catalyst ink, such as the ionomer-to-carbon ratio (<i>I</i>/<i>C</i>) and solid content (SC), play a critical role in determining the structure and performance of the CL. Recently, high-SC inks have attracted increasing attention due to their suitability for large-scale production and their environmentally friendly nature. However, the combined effects of variations in formulation parameters on the structure and properties of CLs in high-SC inks remain poorly understood, posing a challenge to further performance optimization. In this study, a series of high-SC inks with varying SCs and <i>I</i>/<i>Cs</i> were formulated to systematically examine their influence on the structural and functional properties of the cathode catalyst layer. The findings demonstrate the absence of a pronounced coupling effect between the <i>I</i>/<i>C</i> and SC. An increase in the <i>I</i>/<i>C</i> improves the continuity of the ionomer network, although it may contribute to pore blockage in the CL. Moreover, increasing the SC results in a thinner dry film, leading to a reduction in the CL porosity while enhancing the ionomer network connectivity. The trade-off relationship between proton conductivity and oxygen diffusion capacity within high-SC catalyst ink formulations defines an optimal balance of these two parameters. These results provide a crucial foundation for the development and large-scale production of membrane electrode assemblies.