The operation of proton exchange membrane (PEM) fuel cells at intermediate temperatures (100-300oC) creates the advantages of increased catalytic activity and greater resistance to impurities compared to fuel cells operated at lower temperatures. These advantages translate to lower costs due to lower catalyst loadings and lower purity requirements for hydrogen fuel. In addition, the higher temperature results in simpler systems by eliminating the need for humidifiers and reducing the size of radiators. The key limitation to developing this technology is the lack of polymeric membranes and ionomers with the necessary durability and performance characteristics. Los Alamos National Laboratory has developed phosphate-quaternary ammonium ion-pair coordinated PEMs based on cationic membranes prepared by Sandia National Laboratories. The base membranes are poly(phenylene)s with excellent chemical/thermal stability. The ion-paired polymers have very strong interactions between doped phosphate ions and the fixed quaternary ammonium groups which enhances water tolerance under high temperature and low humidity fuel cell conditions. They also have good mechanical properties with low phosphoric acid doping level and allow for the possibility of PEM fuel cells that operate at temperatures above 200 oC. Ion-pair coordinated polymers still have a risk that the acid will be partly evaporated at high temperature operating conditions (&gt; 200°C) or be partly leached out, especially within the electrodes where water is produced. Phosphonic acids can be covalently attached to polymers in order to prevent evaporating or leaching. Because of the impossibility of acid evaporation with phosphonated polymers, the proton conductivity of phosphonated polymers increases with temperature until thermal degradation of the polymers occurs. In this project, we are developing advanced phosphonated ionomers for ion-pair coordinated polymer electrolyte membrane fuel cells to further improve fuel cell performance. This talk will focus on polymer synthesis and will include performance results for systems fabricated with ion-pair membranes and phosphonated polymer ionomers.

Ionomers for intermediate temperature fuel cells with ion-pair membranes

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.