Title

The effects of addition of silicotungstic acid to the electrodes of polymer electrolyte membrane fuel cells

Date of Completion

January 2009

Keywords

Alternative Energy|Engineering, Chemical

Degree

Ph.D.

Abstract

Polymer electrolyte membrane fuel cells (PEMFCs) are promising sources of energy for future portable and transportation applications, but are not currently commercially available due to poor performance at high temperature, and due to high costs associated with platinum in the electrodes. Performance at high temperature is limited due to low proton conductivity of the electrolyte, while high platinum loadings are required to overcome oxygen reduction losses at the cathode. Silicotungstic acid (STA), a heteropolyacid, was added to the electrodes of PEMFCs, since heteropolyacids have been demonstrated to improve proton conductivity in membranes. Performance of fuel cells containing STA in the electrodes was evaluated at various temperature and relative humidity conditions using current scans, cyclic voltammetry and ac impedance techniques. Addition of (STA) is shown to improve activity of PEMFC electrodes at 118°C and 40% RH by as much as 85%, while proton resistance within the electrode is reduced by 50% at 80°C and 20%RH. However, these improvements were only observed at low currents, where kinetic processes dominate. At high currents, gas diffusion resistance increased with addition of STA, suggesting the electrode structure has become less porous. This is likely due to agglomeration of the catalyst particles during electrode manufacturing.^