Performance of polymer electrolyte fuel cell under wet/dry conditions with hydrophilic and hydrophobic electrospun microporous layers

Abstract

The electrospinning method is used to fabricate the microporous layers (MPL). The hydrophobic and hydrophilic electrospun MPLs (E-MPLs) are realized by using acetylene black and pigmented carbon black in the electrospinning ink, respectively. Scanning electron microscope shows that the E-MPLs have three-dimensional inter-connected pore structure formed by disordered nanofibers. Mercury intrusion porosimetry results indicate that the E-MPLs have larger porosity (more than 85%) and wider pore size distribution (0.8–4 μm) compared with the commercial MPL (from SGL 29BC). Hydrophobic E-MPL exhibits lower mass transport resistance at 100% relative humidity (RH) due to its larger pore size and better water drainage capability, while the hydrophilic E-MPL shows lower ohmic resistance at 40% RH due to its higher water retention capability. Fuel cell with a double-layer E-MPL, an integrated MPL containing a hydrophilic layer and a hydrophobic layer, is found to perform well under wider RH range. The fuel cell with double-layer E-MPL is found to have a better dynamic response to a current step, in that it has lower amplitude of voltage undershoot and overshoot, and reaches a steady state more quickly.