Preparation of two-stage microporous layers with gradient pore  structure using pore-making agent for improving the performance of fuel cell

Abstract

In this paper, a gradient pore size structure gas diffusion layer (GDL) was prepared. The pore structure of microporous layers (MPL) were controlled by pore-making agent ammonium bicarbonate (NH4HCO3). The effects of the two-stage MPL and the different pore size structures in the two-stage MPL on the performance of proton exchange membrane fuel cells (PEMFC) were investigated. The results of the conductivity and water contact angle tests showed that the GDL had outstanding conductivity and good hydrophobicity. The results of the pore size distribution test indicated that the introduction of a pore-making agent altered the pore size distribution of the GDL as well as increased the capillary pressure difference within the GDL. Specifically, there was an increase in pore size within the 7-20 μm and 20-50 μm ranges, which improved the stability of water and gas transmission within the fuel cell. The maximum power density of the GDL03 was increased by 37.1% at 40% humidity, 38.9% at 60% humidity, and 40.3% at 100% humidity when compared to the commercial GDL29BC in a hydrogen-air environment. The design of gradient MPL ensured that pore size between carbon paper and MPL changed from an initially abrupt state to a smooth transition state, which greatly improved water and gas management capabilities of proton exchange membrane fuel cell.