Three-dimensional ordered macroporous IrO2 as electrocatalyst for oxygen evolution reaction in acidic medium

Three-dimensional ordered macroporous (3-DOM) IrO2 was synthesized by using the silica colloidal crystal template method and explored as electrocatalyst for oxygen evolution reaction (OER) in acidic medium. X-Ray diffraction (XRD) patterns indicate that the prepared 3-DOM IrO2 has a rutile structure. Images of scanning and transmission electron microscopies suggest that the 3-DOM IrO2 possesses a hierarchical pore structure, in which the honeycomb array of 300 nm primary macropores were cross-linked by secondary mesopores on the walls. The presence of mesopores is also indicated by the N-2 adsorption/desorption isotherms and the small-angle XRD patterns. As compared with IrO2 prepared by conventional colloidal method, the 3-DOM IrO2 exhibited much larger BET area and voltammetric charges. Accordingly, about two and half times enhancement in OER activity was achieved by using 3-DOM IrO2 as the electrode materials, showing prospect of 3-DOM materials in reducing the demand of the expensive IrO2 electrocatalyst for OER in water electrolysis.