Investigation of Silicotungstic acid Modified Platinum Cathodes on Performance and Durability for Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells continue to be of interest for portable power and automotive applications. However, cell performance, durability, and cost continue to be major concerns for wide-spread implementation. Much of the development difficulty is related to the slow kinetics of the oxygen reduction reaction on the platinum-based cathode catalyst. Platinum catalyst is expensive, unstable and can lead to the formation of harmful radicals that result in membrane degradation. The performance and durability issues are exacerbated by the desire to operate at higher cell temperature and lower reactant relative humidity. Elevated temperatures decrease the proton conduction of Nafion� based PEMFCs due to the electrolyte�s dependence on water content, which is limited at low relative humidities. Although attention has been focused on improving membrane conductivity at low relative humidity, of equal importance is the proton conductive layer in the electrode. In this study Silicotungstic acid, a heteropolyacid, was added to the cathode of PEMFCs and evaluated for increased performance and improved platinum stability at high temperature and low relative humidity. Four methods of cathode doping were investigated by physical characterization, electrochemical and single cell testing to see if the activity of Pt could be enhanced for oxygen reduction. Additionally, accelerated degradation of modified cathodes was studied to evaluate if SiWA could reduce loss of catalyst activity from carbon corrosion, Ostwald ripening and dissolution. Performance of modified electrodes was shown to improve activity of the Pt towards oxygen reduction with increased stability of the catalyst.