Ni–Co Codoping Breaks the Limitation of Single-Metal-Doped IrO₂with Higher Oxygen Evolution Reaction Performance and Less Iridium

Synthesizing solid solutions of IrO 2 via doping is known to be a viable approach for effectively using iridium metal by enhancing its intrinsic properties. However, such composites at certain fractional values of dopants realize the substitution limit because of lattice mismatch. Here, on the basis of density functional theory studies and experimentation, we demonstrate codoping as an effective approach to overcome this result with an outstanding oxygen evolution reaction (OER) activity. Nickel and cobalt as the case dopants for the host structure IrO 2 atomically substituted 50% of the precious metal. As a new structural insight, the decreased crystal energy was determined to be the key factor for considerable insertion of dopants. Furthermore, the synthesized codoped IrO 2 reflected an overpotential of only 285 mV at a current density of 10 mA·cm –2, which is appreciably lower than the 320 and 330 mV for individually doping cobalt and nickel, respectively. Our presented approach suggests further OER optimization methods with extensive reduction of precious metals.