Experiment combining molecular dynamics to investigate the effect of deionized water content in dispersant on the ionomer coverage and the structure-effect with output power

The distribution of ionomers within the catalytic layer is a critical factor influencing the output performance of low platinum (Pt) proton exchange membrane fuel cells (PEMFCs). During the preparation of catalyst slurry, the choice of solvent significantly affects the formation of ionomer coverage, characterized by a hydrophobic main chain and hydrophilic side chains. In this study, we employed experimental methods in conjunction with molecular dynamics simulations to investigate the impact of varying ratios of deionized water and isopropanol as solvents on the distribution of ionomers in the catalytic layer. The experimental results indicate that the distribution of ionomers in carbon-loaded catalysts becomes inhomogeneous with an increase in the content of deionized water, particularly regarding the distribution of ionomers on the platinum surface. As the deionized water content rises from 0 % to 50 %, the coverage of ionomers on the platinum surface decreases from 53.7 % to 5.7 %. This inhomogeneous distribution of ionomers can diminish the utilization of the noble metal catalyst and disrupt the proton transport network, ultimately resulting in reduced output performance of the membrane electrode. CO toxicity tests revealed that the electrochemically active area decreased from 42.1 m 2 g −1 to 27.2 m 2 g −1 , a 35.4 % reduction, when the deionized water content in the solvent was increased from 0 % to 50 %. Molecular dynamics simulations demonstrated that the presence of deionized water in the solvent causes the C–F main chains of the ionomers to agglomerate, leading to a more heterogeneous distribution of the ionomers. • The relationship between ionomer distribution and output power is examined in terms of structure-effect dynamics. • Ionomer distribution is investigated by combining experiments with molecular dynamics. • The distribution of ionomers becomes increasingly uneven as the content of deionized water in the solvent.