Unraveling the Blessing and Curse of the IrCu Aerogel Catalyst for the Oxygen Evolution Reaction

Improving the intrinsic activity and utilization of iridium (Ir)-based catalysts for the oxygen evolution reaction (OER) is essential to the market penetration of proton exchange membrane water electrolyzers (PEMWEs). However, conventional electronic structure modulation strategies relying on the introduction of transition metals through alloying and doping face serious stability issues. In this study, we examine the structure–activity–stability relationships toward the OER of an IrCu aerogel in comparison to dispersed IrCu nanoparticles and a commercial IrOx benchmark. Using a combination of ex situ, in situ, and post mortem techniques, we show that the high OER activity of the IrCu aerogel originates primarily from the presence of lattice distortions, i.e., through a structural effect rather than an alloying effect. Moreover, beyond decisively influencing the electrocatalytic activity, the structure is shown to inhibit the formation of stable Ir oxide species during operation unlike for isolated nanoparticles, which is detrimental to the aerogel stability during accelerated stress tests in PEMWE.