Extraordinary acidic oxygen evolution on new phase 3R-iridium oxide

Summary Electrochemical water splitting provides a green pathway for hydrogen generation, while iridium oxide (IrO2) is almost the only stable anode catalyst for acidic media. Yet, it is still a huge challenge to develop an efficient IrO2 catalyst. Here, we demonstrate a microwave-assisted mechano-thermal method that achieves a new 3R phase IrO2. This 3R-IrO2 achieves an ultralow overpotential of 188 mV at the current density of 10 mA cmgeo−2 and a notably high turnover frequency of 5.7 sUPD−1 at 1.50 V versus reversible hydrogen electrode. It also endures limited decay under the current density of 10 mA cmgeo−2 for 511 h prolong test in acidic electrolyte. The new active sites of the edge-sharing structure in 3R-IrO2 and the fast proton transportation along interlayers and intralayers through iridium vacancies contribute to the extraordinary acidic oxygen evolution reaction (OER) activity and stability. This work highlights the great potential of new metastable materials toward advanced electrocatalysis.