Development of Alternated Catalyst Layer Structure for PEM Fuel Cells

Abstract

A novel alternated catalyst layer structure (ACLS) has been developed for fuel cell applications. Sputtering process was applied directly on commercial gas diffusion layer (GDL) by depositing catalyst-forming material and pore-forming material alternately in a nanometer- scale and then removing the pore-forming material. The main physical features of the ACLS are (1) carbon-free and support-free (2) a large amount of void layers/pores, (3) sheet-like catalyst with extended surface and compressed lattice, and (4) a large amount of <111> crystalline planes parallel to catalyst sheet surface. Such characteristics make the ACLS a promising candidate for the PEM cathode application. In this report, some basic evaluation results of the ACLS cathode are presented. Electrochemical surface area (ECSA) evaluations showed that the typical ACLS exhibited a value of 15~30 m2/g and had a high Pt utilization efficiency. For oxygen reduction reaction activity (ORR), the measurement on 5 cm2 fuel cell membrane electrode assemblies showed that an ACLS with 5 nm-thick Pt sheets could increase mass activity 1.5 times and specific activity 3.5 times compared to the commercial Pt/C. Cathode potential at high current densities was evaluated by H2/O2 single-cell test. An ACLS with a Pt loading of 0.07 mg/cm2 demonstrated performance comparable to that of a commercial Pt/C with 0.2 mg/cm2 Pt loading. Excellent durability of the ACLS was also confirmed.