Improvement of the proton exchange membrane fuel cell (PEMFC) performance at low-humidity conditions by adding hygroscopic γ-Al2O3 particles into the catalyst layer

In this study, hygroscopic gamma-alumina particles were added into the catalyst layer of membrane electrode assemblies (MEAs) to improve the wettability and performance of PEMFC at low-humidity conditions. Hygroscopic gamma-alumina particles with a BET surface area of 442 m(2) g(-1) and an average pore diameter of 9 nm were synthesized by a three-step sol-gel procedure. Uniform Pt/C/gamma-alumina catalyst ink was prepared by utilizing an ultrasonic method, and then sprayed on commercial hydrophobic carbon clothes to serve as the catalyst layer. The water contact angles of the catalyst layer with various amounts of gamma-alumina additions 0%, 10%, 20% and 40% were measured to be 1361,1091, 79, and 01, respectively. Effect of adding gamma-alumina particles into the catalyst layer on the single cell performance was investigated under different temperatures of the electrode humidifier. The increased wettability of the cathode catalyst layer with gamma-alumina addition reduced the cell performance due to water flooding, which demonstrates the hygroscopic characteristic of gamma-alumina particles. On the other hand, when the gamma-alumina particles were added into the anode catalyst layer, it was found that the MEA with 10% gamma-alumina addition had the highest Current density at anode humidifier temperatures ranging from 25 to 55 degrees C. Nevertheless, the MEA with 40% gamma-alumina addition into the anode catalyst layer showed the lowest current density because of the high electrical resistance of the catalyst layer and the water flooding in the anode caused by excess water absorption. The increased wettability of the anode catalyst layer by an appropriate amount of gamma-alumina additions also enhances the water adsorption of the anode due to back diffusion. (c) 2008 Elsevier B.V. All rights reserved.