Advanced high current density activity in proton exchange membrane water electrolysis with mass transport enhanced Ir nanodendrites

Shape controlled Ir nanocatalysts have enhanced activity for the oxygen evolution reaction (OER) in acidic conditions, making them promising anode catalyst for proton exchange membrane (PEM) electrolyzer. Notably, Ir nanodendrites show superior activity and durability under both half-cell and membrane electrode assembly configurations. However, the Ir nanodendrites often have limited accessibility to their inner surfaces, causing mass transport overpotential under high current density conditions. Also, domain size of the dendrite branches has not yet been optimized. Here, we report on mass transport enhanced (MTE) Ir nanodendrites and their facile synthesis method. The MTE Ir nanodendrites have larger domain-sized dendrite branches compared to those reported in the literature, but with fewer branches per single dendrite cluster, resulting in overall smaller sizes and larger pore openings. When applied to a PEM water electrolyzer with antimony-doped tin oxide support, the MTE Ir nanodendrites exhibited a 9.1 % enhancement in OER activity at a high current density of 3.0 A/cm2, attributed to a 19 mV improved transport loss. This work provides a promising approach for designing PEM water electrolysis systems for high current density operations.