Achieving ultra-low oxygen transport resistance of fuel cells by microporous covalent organic framework ionomers

Research on ultra-low platinum (Pt)-loaded fuel cells is essential for reducing costs and advancing hydrogen fuel cell commercialization. However, oxygen diffusion resistance remains a major challenge, limiting the oxygen reduction reaction and fuel cell efficiency. To address this challenge, a stable colloidal dispersion of polymer-grafted covalent organic framework (COF) ionomers has been developed. These COF ionomers enhance hydroxide conductivity and oxygen transport by creating a sub-nm porous structure on the catalyst surface, while also dispersing catalyst particles and stabilizing the three-phase interface. Compared to polymer electrodes, COF ionomer electrodes reduce oxygen transport resistance by 96.4%. With ultra-low Pt loading (60 μg cm^-2), COF ionomer electrodes achieve a peak power density of 0.78 W cm^-2, three times higher than that of polymer electrodes. This study presents a promising alternative for the development of more efficient ionomers with low oxygen transfer resistance in fuel cells.