Modification of gas diffusion layers properties to improve water management

Abstract

In this paper we report an approach to improve water management of commercial GDLs by introducing hydrophobicity patterns. Specifically, line and grid patterns have been created in the MPL side by laser radiation. For an in-depth investigation of these modified GDLs the current density distribution was monitored during fuel cell operation. Additionally, the physical properties of these materials were investigated by a number of ex situ methods such as Fourier transform infrared microscopy, electrochemical impedance spectroscopy and water vapor sorption. Furthermore, a comparison of the physical properties of the patterned GDLs with chemically modified GDLs (treated in H 2 SO 4 and H 2 O 2 ) is provided. Our results show a clearly improved homogeneity of current density distribution of the patterned GDLs compared to untreated GDLs. This observation is likely due to a reduced local hydrophobicity which facilitates water diffusion along the flow field of the fuel cell. However, performance of the fuel cell was not affected by the MPL irradiation.

Advancement of Segmented Cell Technology in Low Temperature Hydrogen Technologies

“…Even though the power is not affected by the laser patterning, the current density distribution is more uniform. The extreme values of current density are different by a factor of about 1.5 with patterning, compared to about 2 without [68].…”

“…The GDL has become a focus of modifications of various of its properties [62,63], such as porosity and pore size [64], thickness, microstructures, electrical and thermal conductivity [65], and-obviously-the hydrophobicity [66,67]. In an approach to modify GDLs towards an inhomogeneous hydrophobicity and altered local responses of the fuel cell, laser treatment in the form of lines of 3 mm spacing was applied [68]. Similar approaches have been made with laser perforation [69,70] and ion beam modification [71].…”

Improvement of Oxygen‐Depolarized Cathodes in Highly Alkaline Media by Electrospinning of Poly(vinylidene fluoride) Barrier Layers

“…[34] As a consequence, it is essential to achieve an optimized electrolyte boundary e. g. by a variation of the hydrophobic part of the GDE. In fact, various studies report on the change in hydrophobicity by different techniques, such as a) variation of polymer coating and content, [35][36][37] b) fluorination [38] and c) laser irradiation [39] of the GDEs. However, since these reports refer to fuel cell related applications only, the results can not necessarily be transferred to ODCs.…”