Electrochemically Activated Iridium Oxide Black as Promising Electrocatalyst Having High Activity and Stability for Oxygen Evolution Reaction

In this study, we report a promising approach to greatly enhance the activity of iridium while retaining its high stability. In the approach, electrochemically activated Ir oxide black (A-IrOx-B) is prepared by the selective etching of a less noble component from the binary oxide. Binary IrOs oxide black (IrOsOx-B) was formed by using a solvent-free method, and then an electrochemical activation was performed by the selective etching of Os oxide in order to obtain the activated Ir oxide black possessing high surface area. Interestingly, it was revealed that the oxygen evolution reaction (OER) activity of A-IrOx-B surpassed that of IrOx black and approached that of the state-of-the-art surface-segregated IrRu oxide (S-IrRuOx-B). Most notably, the OER activity of S-IrRuOx-B decreased after stability testing because of the dissolution of Ru, while the activity of A-IrOx-B changed little and eventually surpassed the activity of S-IrRuOx-B.