Catalyst-Support Interactions in Zr₂ON₂-Supported IrO_x Electrocatalysts to Break the Trade-Off Relationship Between the Activity and Stability in the Acidic Oxygen Evolution Reaction

The development of highly active and durable Ir-based electrocatalysts for the acidic oxygen evolution reaction (OER) is challenging because of the corrosive anodic conditions. Herein, IrO_x/Zr₂ON₂ electrocatalyst is demonstrated, employing Zr₂ON₂ as a support material, to overcome the trade-off between the activity and stability in the OER. Zr₂ON₂ is selected due to its excellent electrical conductivity and chemical stability, and the fact that it induces strong interactions with IrO_x catalysts. As a result, IrO_x/Zr₂ON₂ electrocatalysts exhibit outstanding OER performances, reaching an overpotential of 255 mV at 10 mA cm⁻² and a mass activity of 849 mA mg_Ir⁻¹ at 1.55 V (vs the reversible hydrogen electrode). The activity of IrO_x/Zr₂ON₂ is maintained at 10 mA cm⁻² for 5 h, while in contrast, IrO_x/ZrN and an unsupported IrO_x catalyst undergo drastic degradation. Combined experimental X-ray analyses and theoretical interpretations reveal that the reduced oxidation state of Ir and the extended Ir-O bond distance in IrO_x/Zr₂ON₂ effectively increase the activity and stability of IrO_x by altering reaction pathway from a conventional adsorbate evolution mechanism to a lattice oxygen-participating mechanism. These results demonstrate that it is possible to effectively reduce the Ir content in OER catalysts through interface engineering without sacrificing the catalytic performance.