Novel methodology for ex situ characterization of iridium oxide catalysts in voltage reversal tolerant proton exchange membrane fuel cell anodes

摘要

Fuel cell durability with respect to voltage reversal events occurring during start-up/shut-down cycles is of vital importance for stack lifetime in automotive applications. The goal of this work is to describe the activity and durability of oxygen evolution reaction (OER) catalysts in a representative proton exchange membrane fuel cell (PEMFC) anode environment. Three unsupported and one TiO2 supported IrOx OER catalysts are investigated using ex situ accelerated stress testing (AST). The catalysts are ranked based on the ex situ OER activities and the concentration of dissolved Ir in the electrolyte after ex situ AST. Furthermore, the ex situ interaction between IrOx and the hydrogen oxidation reaction (HOR) catalyst PVC is investigated to better understand the voltage reversal performance in fuel cells. The ex situ results are compared with reversal times and reversal time losses (i.e., difference between beginning of test (BOT) and end of test (EOT) reversal times) obtained in a PEMFC subjected to accelerated anode stress test (AAST). Generally, catalysts with higher ex situ OER mass activity and Ir dissolution produced the longest BOT reversal times. The smallest reversal loss (i.e., highest OER durability) is shown by IrOx/TiO2. Regarding unsupported IrOx, heat treatment increasing crystallinity is an effective method to increase OER durability in the fuel cell anode environment.