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

Abstract

The prospect of a CO2 emission free hydrogen energy system requires the develop ment of effective and inexpensive fuel cell catalysts from abundant resources. One promising path forward is the development of anion exchange membrane fuel cells (AEMFC). Thanks to their alkaline environment, they are more flexible regarding catalyst material, thus potentially reducing their cost compared to current fuel cell technology. 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 and high control over composition can be fabricated. Through rotating disk electrode techniques, the oxygen reduction reaction activity of these thin film electrocatysts is 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 to Pt. 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 with respect to cycle-life compared to Pt. This suggests a possible further reduction of catalytic material is on the horizon.