A Model Approach to Uncover the Role of the IrO<sub><i>x</i></sub> Crystallographic Structure and Chemistry on OER Activity and Stability via Annealing a Sacrificial Template
Delphine Clauss, Vincent Martin, Jaysen Nelayah, Raphaël Chattot, P. Bordet, Jakub Drnec, Marta Mirolo, Laëtitia Dubau, Frédéric Maillard
Abstract
Iridium oxide nanoparticles (IrO x NPs) hold promise to lower the catalyst cost of proton-exchange membrane water electrolyzers (PEMWE). However, their enhanced oxygen evolution reaction (OER) activity often comes at the expense of stability. Achieving a delicate balance between these two conflicting properties requires a comprehensive understanding of how the structural, morphological, and chemical characteristics of IrO x NPs influence them. To address this challenge, we synthesized IrO x NPs supported on carbon (IrO x /C), and annealed them in air at temperatures ranging from 340 to 870 °C. We obtained a library of materials, ranging from small, amorphous IrO x NPs supported on carbon to larger self-supported crystalline IrO 2 . Using this library, we evidence the critical role of the IrO x particle size, crystallinity and chemistry on both the OER activity and catalyst stability. We further identify that an annealing temperature of 520 °C provides an optimal balance between OER activity and stability, and we demonstrate size control of unsupported small IrO 2 NPs at temperatures above 500 °C, highlighting the significant role of the sacrificial support in shaping nanostructured IrO 2 catalysts.