Improvement of low-humidity performance of PEMFC by addition of hydrophilic SiO2 particles to catalyst layer

Hydrophilic SiO2 particles are added to the catalyst layer of a fuel cell membrane-electrode assembly (MEA) to improve wettability and performance at low-humidity conditions. The SiO2 added MEAs are prepared by spraying technique and the contact angle is measured by the sessile drop method. The effects of SiO2 additions of 0, 20, 40 and 60wt.% (based on Pt/C) are investigated for various relative humidity levels in the anode and the cathode. The increased wettability of the cathode catalyst layer exerts an adverse effect on cell performance by causing flooding; this result demonstrates the hydrophilicity of SiO2. With 40wt.% addition of SiO2 to the anode catalyst layer, the current density at 0.6V and 0% relative humidity of the anode is 93% of that at 100% relative humidity. By comparison, the performance of a cell using a MEA with no added SiO2 is only 85% of that at 0% relative humidity. A MEA with SiO2 addition in the anode gives a higher performance at 60% relative humidity of the cathode than one with an undoped MEA. Increased wettability of the anode catalyst layer caused by SiO2 addition renders it easy to absorb water from back diffusion.