Effect of the porous electrode geometry on the freezing of supercooled water

Abstract

The supercooled water characteristics in porous electrodes, affect the proton exchange membrane fuel cell (PEMFC) cold starting. This study analyzed the uneven substrate geometry, specifically, the influence of the contact angle and substrate angle on the solidification nucleation rate. For a given temperature, the nucleation rate decreases with increasing contact angle, with less effect as the contact angle exceeds 150°. Experiments observing the freezing of supercooled water in a detached catalyst layer confirmed this result. The simulation also showed that the nucleation rate decreases exponentially with increasing substrate angle: at the 15 K supercooling, with substrate angles increasing by 20°, nucleation rates have a difference of about 10−11 times. Thus, the effect of the substrate geometry cannot be ignored during the freezing of supercooled water in a porous electrode.