Iridium Black (Premetek) as Electrocatalysts for Electrolyzer and Fuel Cell, 0.5 g/bottle, CEFCEIrB

Iridium black is a high-surface-area, metallic form of iridium used as a specialized electrocatalyst in both PEM (Proton Exchange Membrane) electrolyzers and fuel cells. While it shares the same elemental makeup as iridium oxide (IrO2, its metallic state and physical structure give it distinct performance characteristics and trade-offs.

In PEM Electrolyzers (Anode Catalyst), the primary challenge is the Oxygen Evolution Reaction (OER) at the anode. This environment is highly acidic and oxidative, which destroys most metals. (1) Activity vs. Stability: Metallic iridium (Ir-black) is inherently more active than iridium oxide for OER initially. However, it is less stable. During operation, the surface of iridium black naturally oxidizes into a thin, hydrous layer of IrOx$. (2) Performance Evolution: Unlike most catalysts that degrade over time, iridium black often shows an increase in efficiency during the first few hundred hours of operation as the metallic surface "activates" into a more stable oxide form. (3) Standard Benchmarks: Iridium black is considered the industry-standard baseline for OER mass activity, though recent research into supported catalysts (like Ir on TiO2) aims to reduce the high iridium loading (1.0–2.0 mg/cm2) typically required.

In standard hydrogen fuel cells (PEMFC), Platinum (Pt) is the primary catalyst for the Hydrogen Oxidation Reaction (HOR). However, iridium black is often added as a secondary "reversal-tolerant" catalyst. (1) Fuel Starvation Protection: If a fuel cell runs out of hydrogen (starvation), the anode potential can spike. This causes the cell to start "eating" itself by corroding the carbon support. Iridium black facilitates OER at a lower potential than carbon corrosion, essentially providing a "safety valve" that splits water instead of destroying the hardware. (2) Bifunctional Use: In Unitized Regenerative Fuel Cells (URFCs)—devices that can act as both an electrolyzer and a fuel cell—iridium black is essential because it can handle both the HOR (fuel cell mode) and OER (electrolyzer mode) with high efficiency.

Notes: Please try to store the Ir black powder in a dry place.

References: 

1. J. Gao, et al. Revisiting the Activity Gap of Iridium Electrocatalysts for Acidic Water Oxidation, J. Phys. Chem. Lett. 2023, 14, 28, 6494–6505.
2. C. Rakousky, et al. Iridium nanoparticles for the oxygen evolution reaction: Correlation of structure and activity of benchmark catalyst systems, Electrochimica Acta, 2019, 302, 472-477.