Improved Reversal Tolerant Properties of IrO_X as an Anode Electrocatalyst in Proton Exchange Membrane Fuel Cells

Voltage reversal is a severe issue in proton exchange membrane fuel cells (PEMFCs), which can be overcome by adding oxygen evolution electrocatalysts (OER) based on iridium oxide (IrO_X) to the anode catalyst layer. However, the crystal structure and antireversal properties of such anode materials have been rarely investigated. Herein, we report amorphous IrO_X and explore the transformation of crystal structure under heat treatment to examine their antireversal performance in PEMFCs. It is found that heat treatment results in larger catalyst particles which consequences lower OER activity; however, it shows better voltage reverse tolerance (132.2 min). These investigations demonstrate that a balance is crucial between activity and durability in antireversal properties for PEMFCs. Physical characterizations reveal that improved stability and reversal tolerance is attributed to crystallinity and preferred orientation of IrO_X crystals as well as existence of amorphous and crystalline IrO_X. This work proposes a attempt to use the mixed phase IrO_X in the antireversal anode catalyst and highlights the role of corresponding particle size and durability characteristics for the long-term durability of PEMFCs.