An experimental investigation of electro-osmotic drag coefficients in a polymer electrolyte membrane fuel cell

Through the use of a water balance experiment, the electro-osmotic drag coefficients of Nafion 115 were obtained under several conditions (as a function of water content and thermodynamics conditions). For the cases when the anode was fully hydrated (corresponding to water content λ ≈ 14 in the adjacent membrane) and the cathode suffered from drying when dry air was supplied (λ ≈ 2), the electro-osmotic drag coefficients varied from 0.82 (±0.06) to 0.50 (±0.03) H₂O/H⁺ when the current density varied from 0.4 to 1.0 A cm⁻² (95% confidence level). When the current density increased, the electro-osmotic drag coefficient decreased. When the water content at the anode increased from λ ≈ 5 to λ ≈ 14, the cathode was supplied with dry air (λ ≈ 2), and the fuel cell discharged constant current density at 0.6 A cm⁻², the electro-osmotic drag coefficient increased from 0.44 (±0.06) to 0.68 (±0.06) H₂O/H⁺ (95% confidence level). Higher relative humidity gas leads to a higher electro-osmotic drag coefficient at constant current density.