Driving the oxygen evolution reaction (OER) in acidic conditions is a key bottleneck of proton exchange membrane electrolyzer technologies because very few materials can provide reasonable activity and stability. However, Ir-based perovskites, such as SrIrO3, have shown extraordinarily promising performance. A common feature of these materials during OER is metal cation leaching and reaction induced surface amorphization, which forms highly active and stable IrOx moieties. At present, most studies are still based on films or large crystals, which contain electrochemically inert bulk structures that not only reduce atomic utilization of Ir, but also interfere with characterization of the elusive surface structure and active IrOx moieties that are formed in situ. Herein, we present a method to obtain a largely amorphous IrOx nanoparticle material derived from SrIrO3 perovskite that exhibits local structure that is highly consistent with the active moieties formed by previously-published orthorhombic SrIrO3 crystals under OER conditions. This unique IrOx material exhibits an enormous surface area, a promising overall activity, maximized Ir utilization, and unprecedented long-term stability. More importantly, without the signal interference from bulk lattice structures, we are able to more directly characterize the properties of these active moieties at the atomic level. From a series of state-of-the-art characterization techniques, including in situ and ex situ x-ray absorption spectroscopy, high resolution microscopy, electron- and x-ray-based pair distribution function and differential electrochemical mass spectrometry, we discover novel IrOx moieties with short-range order in the “surface amorphous layer” and monitor their atomic structural and mechanistic evolution during long-term OER electrolysis. This work not only provide an accessible approach to fabricate high atomic utilization Ir-based OER electrocatalysts, but also provides detailed OER mechanistic insights.

Short-range ordered IrOx moieties derived from SrIrO3 perovskite towards efficient and stable oxygen evolution reaction

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.