Activity and Stability of Pt/IrO2 Bifunctional Materials as Catalysts for the Oxygen Evolution/Reduction Reactions

Pt/IrO2 bifunctional catalysts synthesized with varying Pt:Ir ratios and characterized using several techniques, including energy dispersive X-ray spectroscopy, transmission electrons microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, were investigated for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in acid media. Three stability testing protocols are used to evaluate the catalysts stabilities, comprising electrode cycling in the ORR, OER, and ORR–OER potential ranges. Electrochemical results provide evidence that a Pt/IrO2 1:9 material exhibits better balance between the OER and ORR mass activities and that cycling in the ORR-OER potential window is the most aggressive aging protocol for the Pt/IrO2 materials. Identical location transmission electron microscopy is used to investigate the aging processes taking part in the Pt/IrO2 catalysts. In addition to dissolution processes, particle coalescence, growth, and detachment are confirmed as responsible for the Pt/IrO2 instability.