Amorphization mechanism of SrIrO ₃ electrocatalyst: How oxygen redox initiates ionic diffusion and structural reorganization

Abstract

The use of renewable electricity to prepare materials and fuels from abundant molecules offers a tantalizing opportunity to address concerns over energy and materials sustainability. The oxygen evolution reaction (OER) is integral to nearly all material and fuel electrosyntheses. However, very little is known about the structural evolution of the OER electrocatalyst, especially the amorphous layer that forms from the crystalline structure. Here, we investigate the interfacial transformation of the SrIrO₃ OER electrocatalyst. The SrIrO₃ amorphization is initiated by the lattice oxygen redox, a step that allows Sr²⁺ to diffuse and O^2- to reorganize the SrIrO₃ structure. This activation turns SrIrO₃ into a highly disordered Ir octahedral network with Ir square-planar motif. The final Sr <i>_y</i> IrO <i>_x</i> exhibits a greater degree of disorder than IrO <i>_x</i> made from other processing methods. Our results demonstrate that the structural reorganization facilitated by coupled ionic diffusions is essential to the disordered structure of the SrIrO₃ electrocatalyst.