Ultra-Low Loading IrO2 on Porous Transport Layer for Catalysis of Proton Exchange Membrane Water Electrolysis

Abstract

Proton Exchange Membrane Water Electrolysis (PEMWE) is a commercial technology with specific advantages such as high-power density and rapid start-up times, which makes it a perfect match to produce hydrogen from intermittent renewable energy sources (green H2). [1] However, very scarce materials, such as iridium and platinum, are currently used as catalysts and protection coatings to withstand the harsh operating conditions in PEMWE. Iridium is the anode catalyst in the state-of-the-art PEMWE, with loadings in the range 1-2 mg/cm2. This metric translates into using 200-500 kg of iridium per GW, which accounts for roughly 10% of the global iridium production per year. Reducing iridium usage in PEMWE is critical to realize the 10-100 GW/year growth in green H2 power. [2,3]To significantly reduce the Ir loading, while maintaining the lateral conductivity, we coated the iridium catalyst by atmospheric spatial Atomic Layer Deposition (sALD) on titanium porous transport layer (PTL), which acts as the electrically conductive substrate. The coating renders ultra-low iridium loadings, which is 100-200 times less iridium than the state-of-the-art catalyst coated membrane technology, while retaining ca. 60-80% of the performance (in terms of current density), with durability demonstrated up to 100 h (see Figure 1). We will also show here that protection coatings on the titanium PTL are beneficial to yield good durability with these ultra-low loadings of iridium and demonstrated that sALD has the potential to produce non-PGM based protection coatings.[1] Barbir, F. Solar Energy 78 (2005) 661-669.[2] Gavrilova, A., Wieclawska, S.M. “Towards a green future. Part 2” (2021). TNO report 21-12158.[3] Minke, C., Suermann, M., Bensmann, B., & Hanke-Rauschenbach, R. J. Hydrogen Energy 46 (2021) 23581-23590. Figure 1