Fig. 5: Ultrafast reaction mechanism of CeO2–IrO2.

a, An fs-ECTAS of CeO2–IrO2 at 1.9 V versus RHE. b, An fs-ECTAS of IrO2 at 1.9 V versus RHE. Arrows indicate the characteristic signal peaks assigned to IrO2, Ir6+ and H+ species, respectively. c, A schematic illustration of the time-resolved catalytic mechanism for CeO2–IrO2 and IrO2. IrVo denotes the lattice vacancy formed after Ir dissolution.