Effect of the silica particle diameter on the morphology of catalyst layer in proton exchange membrane fuel cells

Providing sufficient hydration in a proton exchange membrane fuel cell is important to obtain high fuel-cell performance under a low relative humidity (RH) condition. Herein, we investigated the influence of the silica (SiO2) particles on the agglomerated structure in the catalyst layer (CL). The CLs were prepared with three different particle diameters namely 8, 30 and 100 nm and their water uptake (WU) behavior and the electrochemical properties were subsequently characterized. As a result, the CL containing 8 nm SiO2 particles showed intimate contact between the SiO2 particles and Nafion ionomer, thereby improving the electrochemical surface area and WU behavior. Consequently, it is clearly demonstrated that the cell polarization of the 8 nm SiO2-containing CL presented 1.042 A cm(-2) at 0.5 V under 20% RH condition, which exhibited 2.94 times higher than that of the CL without the addition of SiO2.