Proton Exchange Membranes Based on Polymeric Ionic Liquids for Fuel Cell Applications

Abstract

One of the most promising technologies for power generation are Proton Exchange Membrane Fuel Cells (PEMFCs). PEMFCs are electrochemical devices which convert directly the chemical energy of oxidation-reduction reactions into electrical energy. These electrochemical devices have high electric efficiency and low environmental impact [1]. Several authors are working in the upcoming commercialization of this technology. However, there are technical aspects that must be overcoming before their implementation. The proton exchange membrane, which is the key component of a PEMFC, needs a considerable improvement regarding its performance without external humidification [2]. This is of great importance because it allows working at temperatures above 80 ºC and eliminate the management of water. Concerning this aspect, many authors are working incorporating ionic liquids as proton exchange components in PEMFCs. Ionic liquids, which are in liquid state at room temperature, have attractive properties for this application, such as thermal and electrochemical stability and high anhydrous conductivity. There are several strategies in order to incorporate ionic liquids inside the proton exchange membrane. One of them deals with the polymerization of an ionic liquid monomer [3]. This option avoids the leak of the ionic component during the fuel cell operation. In this work, membranes based on polymeric ionic liquids have been designed for their use as electrolytes without external humidification. For this purpose, the ionic liquids 1-(4-sulphobutyl)-3-vinylimidazolium trifluoromethanesulphonate [HSO3-BVIM][OTF], 1-sulfobutyl-3-metylimidazolium 2-sulfoethylmethacrylate [SBMIm][SEM] and 1-sulfobutyl-3-vinylimidazolium 2-sulfoethylmethacrylate [SBVIm][SEM] were polymerized under ultraviolet light. The ionic conductivity and fuel cell performance were tested without external humidification.