WxC thin films supports for Cathode Catalysts in Anion Exchange Membrane Fuel Cells

Sammanfattning

The prospect of a CO2 emission free hydrogen energy system requires the develop ment of effective and inexpensive fuel cell catalysts from abundant resources. Onepromising path forward is the development of anion exchange membrane fuel cells(AEMFC). Thanks to their alkaline environment, they are more flexible regardingcatalyst material, thus potentially reducing their cost compared to current fuel celltechnology.In this study, WxC thin films are evaluated as support for different catalytic mate rials with the aim to reduce catalyst loading and increase specific current density.Using sputtering and physical vapour deposition, thin films with high uniformity andhigh control over composition can be fabricated. Through rotating disk electrodetechniques, the oxygen reduction reaction activity of these thin film electrocatystsis measured in alkaline media. Tested catalystic thin films are Pt, Pd, Cu and Ag.Pt and Pd show good onset potential and an improved mass activity compared toPt. Cu and Ag evaporated on WxC exhibit less ORR activity in alkaline media.The results also indicate that WxC improves the stability of very thin Pt layers withrespect to cycle-life compared to Pt. This suggests a possible further reduction ofcatalytic material is on the horizon.