Effective Catalyst Layer Structures for High Performances Proton Exchange Membrane Fuel Cell (PEMFC）

Abstract

Membrane electrode assembly (MEA) consists of three parts which are electrolyte membrane, catalyst layer and gas diffusion layer, determining electrochemical single cell performances. Catalyst layer and diffusion layer influence mass transport including proton conduction and fuel diffusion. In this study, the effects of gas diffusion layer having microporous layer and catalyst layer structures fabricated by spraying and screen printing were investigated by measuring porosity of catalyst layer and I-V polarization curves of MEA. Microporous layer coated with carbon nanoparticles on gas diffusion layer enhanced mass transport reducing concentration polarization, which improves the electrochemical performances. Microporous layer also alleviated interfacial problems between membrane and catalyst layer, when catalyst layer is coated on gas diffusion layer(GDL). Catalyst layer fabricated by screen printing method on microporous layer has very uniform pore with size of 0.23 ㎛ and no cracks on surface, even after hot pressing, while spraying method forms agglomerates on the surface of catalyst layer with various sized pores. Consequently, screen printing optimized to microporous layers improved electrochemical performance (1000 mA cm-2 at 0.6V and 2200mA cm-2 at 0.4V) by lowering ohmic resistance and mass transfer overpotential, compared to MEA fabricated by spraying method.