Effect of Dispersion Solvents in Catalyst Inks on the Performance and Durability of Catalyst Layers in Proton Exchange Membrane Fuel Cells

Chan-Ho Song,Jin-Soo Park

doi:10.3390/en12030549

Abstract

Five different ionomer dispersions using water–isopropanol (IPA) and N-methylpyrrolidone (NMP) were investigated as ionomer binders for catalyst layers in proton exchange membrane fuel cells. The distribution of ionomer plays an important role in the design of high-performance porous electrode catalyst layers since the transport of species, such as oxygen and protons, is controlled by the thickness of the ionomer on the catalyst surface and the continuity of the ionomer and gas networks in the catalyst layer, with the transport of electrons being related to the continuity of the carbon particle network. In this study, the effect of solvents in ionomer dispersions on the performance and durability of catalyst layers (CLs) is investigated. Five different types of catalyst inks were used: (i) ionomer dispersed in NMP; (ii) ionomer dispersed in water–IPA; (iii) ionomer dispersed in NMP, followed by adding water–IPA; (iv) ionomer dispersed in water–IPA, followed by adding NMP; and (v) a mixture of ionomer dispersed in NMP and ionomer dispersed in water–IPA. Dynamic light scattering of the five dispersions showed different average particles sizes: ~0.40 μm for NMP, 0.91–1.75 μm for the mixture, and ~2.02 μm for water–IPA. The membrane-electrode assembly prepared from an ionomer dispersion with a larger particle size (i.e., water–IPA) showed better performance, while that prepared from a dispersion with a smaller particle size (i.e., NMP) showed better durability.

Highlights

Enhancement of the performance and durability of proton exchange membrane fuel cells (PEMFCs), resulting in cost reduction in fuel cells, is essential for their commercialization [1,2,3].The performance and durability of PEMFCs are typically determined by the polymer electrolyte membrane, which are mostly made of perfluorinated sulfonic acid (PFSA) and porous electrodes comprising electrocatalysts and an ionomer binder in membrane-electrode assemblies (MEAs) [3,4,5,6]
It has been reported that the distribution of ionomer within the carbon supported electrocatalyst (e.g., Pt/C) plays an important role in the design of high-performance porous electrode catalyst layers (CLs), as the transport of species such as oxygen and protons is controlled by the thickness of the ionomer on the catalyst surface and the continuity of the ionomer and gas networks in the CL, with the transport of electrons being related to the continuity of the carbon particle network [11,12,13,14,15,16]
CLs investigated to the substantial effect of solvents on the morphology of ionomers dispersed in the various solvent the substantial effect of solvents on the morphology of ionomers dispersed in the various solvent systems, on the structure of the electrode surface, and on

Summary

Introduction

Enhancement of the performance and durability of proton exchange membrane fuel cells (PEMFCs), resulting in cost reduction in fuel cells, is essential for their commercialization [1,2,3].The performance and durability of PEMFCs are typically determined by the polymer electrolyte membrane ( called an ionomer membrane), which are mostly made of perfluorinated sulfonic acid (PFSA) and porous electrodes comprising electrocatalysts and an ionomer binder in membrane-electrode assemblies (MEAs) [3,4,5,6]. Optimization of porous electrodes has been achieved by controlling relative amounts of the ionomer and/or electrocatalyst if the polymer electrolyte membranes are fixed [7,8,9,10]. It has been reported that the distribution of ionomer within the carbon supported electrocatalyst (e.g., Pt/C) plays an important role in the design of high-performance porous electrode catalyst layers (CLs), as the transport of species such as oxygen and protons is controlled by the thickness of the ionomer on the catalyst surface and the continuity of the ionomer and gas networks in the CL, with the transport of electrons being related to the continuity of the carbon particle network [11,12,13,14,15,16].

Methods

Results

Conclusion