Plasma Membranes Modified by Plasma Treatment or Deposition as Solid Electrolytes for Potential Application in Solid Alkaline Fuel Cells

Abstract

In the highly competitive market of fuel cells, solid alkaline fuel cells using liquid fuel (such as cheap, non-toxic and non-valorized glycerol) and not requiring noble metal as catalyst seem quite promising. One of the main hurdles for emergence of such a technology is the development of a hydroxide-conducting membrane characterized by both high conductivity and low fuel permeability. Plasma treatments can enable to positively tune the main fuel cell membrane requirements. In this work, commercial ADP-Morgane® fluorinated polymer membranes and a new brand of cross-linked poly(aryl-ether) polymer membranes, named AMELI-32®, both containing quaternary ammonium functionalities, have been modified by argon plasma treatment or triallylamine-based plasma deposit. Under the concomitant etching/cross-linking/oxidation effects inherent to the plasma modification, transport properties (ionic exchange capacity, water uptake, ionic conductivity and fuel retention) of membranes have been improved. Consequently, using plasma modified ADP-Morgane® membrane as electrolyte in a solid alkaline fuel cell operating with glycerol as fuel has allowed increasing the maximum power density by a factor 3 when compared to the untreated membrane.

X‐Ray Reflectometry Characterization of Plasma Polymer Films Synthesized from Triallylamine: Density and Swelling in Water

“…[14] Parallel, we have shown that the hydroxide conductivity of plasma polymers synthesized from triallylamine was decreasing with the average discharge power, which has been attributed not only to the decreasing content of sp 3 N-C functions in films but also hypothetically to the increase of the film density. [14] Lastly, it has been shown in another recent paper by our group that water retention of a commercial hydroxide-exchange membrane could be enhanced by the addition of a triallylamine-based plasma polymerized film on its surface, due to quite poor water sorption and diffusion capabilities of the plasma film directly related to its high cross-linking degree. [15] One objective of the present study is to determine the film density and water swelling of plasma films prepared from triallylamine and to depict their evolution as a function of the average discharge power as the main plasma synthesis parameter.…”

“…At higher average powers (above 40 W), in the monomer deficient region, the growth rate of films decreases with P A and the structure of the films presents an increasing content of sp 2 N¼C, N-N, and N-O bonds at the expense of sp 3 N-C ones. [14] Moreover comparison between the composition in the bulk and at the film surface has shown that the bulk composition is 5 at.% less enriched in oxygen than the film surface, which is due to a pollution of the latter by atmospheric oxygen once returning the samples to room environment after plasma deposition. [14] In an attempt to introduce quaternary ammonium functions in the films (best hydroxide conducting groups), the latter were treated with methyl iodide (quaternization treatment).…”

“…[14] Moreover comparison between the composition in the bulk and at the film surface has shown that the bulk composition is 5 at.% less enriched in oxygen than the film surface, which is due to a pollution of the latter by atmospheric oxygen once returning the samples to room environment after plasma deposition. [14] In an attempt to introduce quaternary ammonium functions in the films (best hydroxide conducting groups), the latter were treated with methyl iodide (quaternization treatment). Unfortunately, the efficiency of the postquaternization procedure could not been proved by XPS measurements.…”

“…We have recently shown that plasma polymers synthesized from triallylamine are dense and uniform thin films characterized by thicknesses from some hundred nanometers to some micrometers and a polyethylene-type structure containing a mixture of nitrogen-and oxygenbased functions. [14] It has been found that the growth rate and the chemical structure of the triallylamine plasma films are directly correlated with the average power of the plasma discharge (P A ). Two different regimes have been observed in the plasma deposition of triallylamine.…”

“…Another objective of this work is to correlate the film density and water swelling with the hydroxide conductivity previously investigated. [14] The method of choice for this study is X-ray reflectometry (XRR), which can be used to accurately determine some morphological parameters of thin films, such as density and layer thickness.…”