Molecular dynamics study on heterogeneous condensation in the gas diffusion layer of proton exchange membrane fuel cells (PEMFCs)

During proton exchange membrane fuel cells (PEMFCs) operation, water vapor condensation on the gas diffusion layer critically affects mass transport and cell performance. Although heterogeneous condensation has been widely studied, the microscopic role of hydrogen as a background gas in multicomponent condensation systems remains insufficiently understood. In the present study, molecular dynamics simulations were conducted to investigate the heterogeneous condensation behavior of H₂O-H₂ mixtures on graphene surfaces under hydrogen-rich conditions. The effects of surface wettability, hydrogen content, and cooling temperature on condensation dynamics were systematically analyzed. Increasing the solid–liquid interaction parameter from 0.7 to 1.0 reduced the contact angle on graphene from 78.34° to 39.69°, promoting faster water adsorption and cluster formation. At a fixed cooling temperature of 333.15 K, increasing the hydrogen content raised the cooling pressure from 2 bar to 3 bar, causing the H₂O diffusion coefficient to decrease from 0.0028 cm2/s to 0.0025 cm2/s. Meanwhile, the interaction potential energy between H₂O and graphene increased, indicating that hydrogen molecules facilitate water aggregation and accelerate heterogeneous condensation near the graphene surface. When the number of H₂ molecules was fixed, decreasing the cooling temperature from 353.15 K to 333.15 K reduced the thermal relaxation time constant from 1010.47 ps to 974.13 ps, corresponding to enhanced interfacial thermal conductance. Meanwhile, latent heat release during condensation intensified temperature fluctuations in the hydrogen phase. These findings clarify the influence of hydrogen background gas on multicomponent heterogeneous condensation and provide theoretical support for hydrothermal management in PEMFCs.