Surface‐Segregated IrCo Nanoparticles on CoO Nanosheets with Ultralow Ir Loading for Efficient Acidic Water Splitting

Abstract IrO 2 is the benchmark catalyst for acidic oxygen evolution reaction (OER), however, the high cost and low earth abundance hinder its large‐scale application. Herein, surface‐segregated IrCo nanoparticles on CoO nanosheets with a strong electronic interaction are synthesized through the ion exchange‐pyrolysis method. The resulting IrCo−CoO heterostructures, containing an ultra‐low Ir content of 4.73 wt %, demonstrate exceptional performance in the acidic OER. The catalyst exhibits a low overpotential of 270 mV at a current density of 10 mA cm −2 and remarkable stability, with noticeable activity decay observed only after 140 hours of continuous operation. These results surpass most reported Ir‐based electrocatalysts. Specifically, the mass activity at the overpotential of 300 mV for the IrCo−CoO catalyst reaches 124.52 mA mg Ir −1 , which is 20 times higher than that of commercial IrO 2 . Furthermore, we constructed a home‐made overall water splitting cell utilizing IrCo−CoO heterostructures as both anode and cathode electrodes, achieving a current density of 10 mA cm ‐−2 at a voltage of 1.51 V. Our findings present a promising strategy for designing high‐efficient catalysts with significantly reduced noble metals loading.