Optimization of ionomer distribution and oxygen transport in hydrogen fuel cell electrodes through carbon support surface functionalization: A molecular perspective study

Improving oxygen transport efficiency in electrodes is crucial for developing high-performance proton exchange membrane fuel cells. Since the oxygen transport paths in catalytic layer are composed of ionomers, optimizing the distribution of ionomers is key to enhancing oxygen transport efficiency. Here we employ molecular dynamics simulations to illustrate the significant potential of functional group (-OH, -COOH, -NH₂) modification of catalyst carbon supports in optimizing ionomer distribution and enhancing oxygen transport. The results demonstrate that the hydrophilicity of the functional groups attracts water molecules, which compress the hydrophobic ionomer backbone and decreasing its gyration radius by 1.51 %∼16.42 %. Surface functionalization effectively lowers the oxygen transport barrier in the rapid dissolution and diffusion regions, especially the -OH group. The oxygen solubility in the diffusion region increased by 91.75 %, 36.94 %, and 23.30 % for -OH, -COOH, and -NH₂ functionalized systems, respectively, which is fundamentally attributed to two factors: the increased cavity space at the Nafion/O₂ interface and the tortuosity reduction of the oxygen transport channel by the functional groups acting as hydrophilic anchor points. These insights offer a foundation for the future optimization of fuel cell performance through precise control of the chemical and physical properties of electrode interfaces.