High-performance sulfonated poly(arylene ether) as a catalyst binder for enhanced efficiency in proton exchange membrane fuel cells

Abstract

The design of high-performance catalyst binders remains a critical challenge in advancing renewable energy technologies including fuel cells and electrolyzers. Herein, we report the design and composition optimization of a novel catalyst binder, designated as SP4 (sulfonated poly(arylene ether)), tailored for proton exchange membrane fuel cells (PEMFCs). Our results reveal that among all the evaluated compositions, the SP4 20 (comprising 20 wt% SP4 ionomer in a 20 wt% methanol–water system) exhibits the highest power output, representing 15 % and 147 % improvement over SP4 30 and SP4 40 formulations, respectively. Microstructural analysis of SP4 20 reveals a highly uniform catalyst dispersion and an interconnected porous architecture within the catalyst layer (CL), which allows efficient reactant diffusion and maximizes electrochemically active surface area (54.01 m²/g). When paired with the SP4 membrane, the integrated membrane electrode assembly (MEA) achieves a peak power density of 956  mW/cm², outperforming Nafion-based MEA (931 mW/cm²) and highlighting the benefits of membrane-electrode compatibility. Comparative analysis with contemporary binder systems reported in the literature indicates that SP4 delivers superior performance, which establishes it as one of the most promising ionomer binders developed to date. These findings designate SP4 as a high-performance and structurally optimized ionomer binder with considerable potential for next-generation PEMFC systems.