Development of unsupported IrO2 nano-catalysts for polymer electrolyte membrane water electrolyser applications

Abstract

IrO₂ is a current state-of-the-art catalyst for polymer electrolyte membrane water electrolyser (PEMWE) applications due to its high stability during the oxygen evolution reaction (OER). However, its activity needs to be significantly improved to justify the use of such a high-cost material. In this study, the activity of the IrO₂ catalyst was improved by optimising and comparing two synthesis methods: the modified Adams fusion method (MAFM) and the molten salt method (MSM). Optimum OER performances of the IrO₂ catalysts synthesised with the two synthesis methods were obtained at different temperatures. For the MAFM, a synthesis temperature of 350 °C produced the IrO₂ catalyst with an overpotential of 279 mV and the highest OER stability of ~ 82 h at 10 mAcm⁻². However, for the MSM, the lowest overpotential of 271 mV was observed for IrO₂ synthesised at 350 °C, while the highest stability of ~ 75 h was obtained for the IrO₂ synthesised at 500 °C.

Significance:

IrO₂ is still currently a state-of-the-art catalyst in PEMWE due to its high stability in the highly acidic and oxidising conditions of the OER. High-performance IrO₂ catalysts were successfully produced via the MAFM and MSM. Both the MAFM and MSM are simple and easily scalable for high-volume production of metal oxide catalysts. This study showed that the physical/structural properties of the IrO₂ catalysts can be tailored through synthesis methods and synthesis conditions to improve their OER performance.