Investigation of the Effect of Electrolyte Velocity on Mass Transport in Porous Electrodes Utilizing A Symmetric Cell

A symmetric cell using Fe2+/Fe3+ as a redox couple at both sides was fabricated to investigate the impact of electrolyte velocity on mass transport in porous electrodes. Polarization behaviors were measured at different velocities ranging from 1.7 to 20 mm s(-1). The significant mass transport loss is observed at velocities lower than 5 mm s(-1) even though the reactant stoichiometry is high enough. Starting from the lowest velocity of 1.7 mm s(-1), the improvement of cell performance with the increase of velocity is initially significant, which becomes minor as the velocity reaches a high value above 10 mm s(-1). According to the experimental results, velocities lower than 5 mm s(-1) should be avoided in designing flow batteries to prevent significant mass transport loss, while those higher than 20 mm s(-1) are not recommended because the slight benefit might be overweighed by the increment of pumping loss.