Heteropoly acid Immobilization and Crosslinking in a Polymer Electrolyte Membrane for Fuel Cell Ruth Anyaeche, Andrew Motz, Mei-Chen Kuo, James L. Horan, Andrew M. Herring Renewable Energy Material Research Science and Engineering Center Department of Chemical and Biological Engineering, Colorado School of Mines Golden CO

CHEMISTRY OF FUEL CELL At anode: 2H2 ⇒4H + 4e At Cathode O2 + 4H + 4e ⇒2H2O Net Reaction 2H2 + O2 ⇒2H2O

Objective of Research Heteropoly acid (HPA) attachment and cross-linking in a novel fuel cell polymer membrane Determine how the polymerization condition is suitable for maximizing the attachment of HPA fully to the polymer solution by annealing time and temperature in the K+ and H+ form.

HPA is a good proton conductor at hotter and drier conditions in a fuel cell Covalent bonding to the polymer prevents the HPA from washing out Cross-linking improves mechanics

Characterization Technique HPA (70wt%)added to polymer solution with the H+ catalyst Anneal to further attach the HPA

Boil in H2O for 1 hour Anneal each piece at different temperature and time in K+ and H+ form Soak in H2O for 16 hours

Measure membrane and perform EDX to determine the %HPA immobilized. Conductivity measurement determine membrane performance

After Ion Exchange – 50% HPA left Soaked in water – 40% Retained Boiled in water – 20-30% left

Concentrated solution (Sample 5) at high temperature and time in K+ form but no H+ form Dilute Solution (Sample 21 and 22) annealed at different temperature and time in K+ form and H+ form

Different temperature of 92RH at 130℃ with 2&24 hours anneal time

Concentrated solution (Sample 5 and 6), were Annealed at high temperature for 24hrs in the k+ form but not in the H+ form Dilute solution (sample 22), annealed at a low temperature for 24hrs in the k+ form and also in the H+ form Conductivity (S/cm) at 92%RH is stable, too high and has the world polymer membrane record

As the temperature increased, the conductivity and conductivity temperature increased

A concentrated solution annealed at a higher temperature and time is most preferable in a membrane of a PEM fuel cell application. Using the SEM/EDX result, the more HPA in the membrane the better the proton conductivity At higher temperature the molecules are moving faster for a better proton conductivity( increase in temperature increases conductivity).

Anneal films at 80℃ for 2hours Try different annealing time between the range of 16-12 hours in order to improve the performance of the membrane. The use of methanol instead of Dmac and crosslinking for flexibility especially the concentrated solution.

Acknowledgement We thank the Renewable Energy material Research science and Engineering center, Colorado fuel cell center and Colorado school of mines for support and assistance through out this project. Special thanks to my Advisor, all the members of Dr. Herrings Lab and all those who have supported the research experience Thanks to APS CUWiP for giving the opportunity and the sponsorship

Reference Shin R. Mukai “immobilization of Heteropoly acid in the network structure of carbon gels” Applied Catalysis December (2003) : 99- 105. web