Nanocomposite Polymer Membranes for Fuel Cells

Dear Colleagues,

The polymer electrolyte is the key component of several fuel cell technologies, from those fed with a liquid fuel (e.g., methanol) or oxidant (e.g., hydrogen peroxide), operating essentially at low temperatures and under wet conditions, to those running on hydrogen and oxygen gases, which should operate at higher temperatures. Single-phase polymer electrolytes often display insufficient performance; the ionic conductivity is low, or the liquid permeation is high. They may also display insufficient thermal, chemical and mechanical stabilities. These limitations restrain the development of fuel cell technologies for an extended and highly-desirable range of operational conditions, namely high temperatures or low humidity, due to either low conductivity or the lack of stability, or the operation with liquid fuels and oxidants due to excessive fuel/oxidant permeation.

The aim of this Special Issue is to gather an ensemble of review or original research works that are representative of the various approaches in the design of nanocomposite polymer electrolytes displaying decisive advantages over single-phase membrane separators on their main limitations.

The design of nanocomposites with a suitable combination of components offers a vast range of possibilities for the design of novel polymer-based electrolytes with enhanced global performance, taking advantage also of the high matrix/filler interfacial area and of extraordinary non-trivial size effects. For example, high levels of protonic (and also hydroxyl) conductivity have recently been disclosed for many organic-inorganic hybrid nanostructured materials that have potential application as fillers. Some of these materials are microporous or mesoporous, which means that in addition to potentially fast ion transport paths, they also contribute to reduce swelling of a polymeric matrix. Other examples are the carbon-based fillers like graphene, graphene oxide or nanotubes, which can be functionalized on the surface for enhanced ionic transport and can be extremely active to reduce liquid permeation due to their particular aspect ratio. Novel composite designs may also open new horizons in the development of environmentally friendly membranes by combining biopolymers with suitable fillers with the complementary functional properties. This contributes to link the "green" fuel cell technology to an environmentally sustainable materials paradigm, which so far has not been a major concern in fuel cell research.

Your recent developments of nanocomposite polymer electrolytes on these and other topics are very welcome.

Dr. Filipe M.L. Figueiredo
Guest Editor

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