Ir-Surface Enriched Porous Ir–Co Oxide Hierarchical Architecture for High Performance Water Oxidation in Acidic Media

The large-scale application of acidic water electrolysis as a viable energy storage technology has been hindered by the high demand of precious metal oxides at anode to catalyze the oxygen evolution reaction (OER). We report an Ir-Co binary oxide electrocatalyst for OER fabricated by a multistep process of selective leaching of Co from Co-rich composite oxides prepared through thermal decomposition. The stepwise leaching of the Co component from the composites leads to the formation of macro- and mesoscale voids walled by a cross-linked nanoporous network of rod- and wedge-like building units of Ir-Co binary oxide with a rutile phase structure and an Ir-enriched surface. In comparison, Ir-Co binary oxide with similar composition prepared by direct thermal decomposition method exhibits a loose nanoparticle aggregation morphology with a Co-enriched surface. The cross-linked porous Ir-Co binary oxide from selective leaching is about 3-fold more active for the OER than that from direct thermal decomposition. Compared with pure IrO2 from thermal decomposition, the Co-leached binary oxide is ca. two times more active and is much more durable during continuous oxygen evolution under a constant potential of 1.6 V, thus showing a possibility of reducing the demand of the expensive and scarce Ir in OER electrocatalyst for acidic water splitting.