Iridium-Based Mixed Transition Metal Oxide (Ir₃MO_x, M = Ni, Co, Fe) Incorporated in the Conducting Layer as an Electrocatalyst for Boosting the Oxygen Evolution Reaction

Ir₃MO_x@CMI (M = Ni, Co, Fe) electrocatalysts are explored for the oxygen evolution reaction by embedding Ir₃MO_x within carbon matrix islands (CMIs) in direct contact with a titanium porous transport layer. Structural and compositional analyses reveal that incorporating transition metals not only enhances Ir particle dispersion but also modifies the morphology. The unique hierarchical structure of the Ir₃MO_x@CMI electrocatalyst improves its intrinsic OER activity and durability under severe acidic conditions. Among the electrocatalysts, Ir₃CoO_x@CMI demonstrates the highest intrinsic OER activity, achieving an overpotential of 233 mV at 10 mA cm⁻², alongside a minimal charge transfer resistance of 1.57 Ω cm² and a Tafel slope of 57 mV per dec. Additionally, it exhibits superior stability during both accelerated degradation testing (10k cycles) and chronopotentiometry over 200 h at 10 mA cm⁻² in a half-cell stage, with a degradation rate of 35 µV h⁻¹. Furthermore, this catalyst demonstrates improved water-splitting performance in the unit cell stage, achieving a cell voltage of 1.55 V at 1 A cm⁻² while maintaining stability over 500 h at a current density of 1 A cm⁻². These findings position Ir₃CoO_x@CMI as a promising candidate for sustainable hydrogen production in proton exchange membrane water electrolysis applications, offering enhanced performance and reduced Ir consumption.