Porphyrin-Confined\nSupported Ultrasmall Ir Clusters\nas Oxygen Evolution Catalysts for Water Electrolysis

Metalloporphyrin\nligands themselves can participate in\nthe redox\nprocess, making them beneficial in promoting the multielectron catalytic\nprocess of the oxygen evolution reaction (OER). However, OER catalysts\nsynthesized by traditional chemical strategies face challenges in\nwater electrolysis. We synthesized high-performance and stable alkaline\nand acidic OER electrocatalysts loaded with ultrasmall iridium clusters\nby taking advantage of the attraction and confinement of Ir atoms\nby the Ir–N bonds formed by the porphyrin cavity. The N in\nthe porphyrin cavity forms an Ir–N bond with Ir so that Ir\ncarries a negative charge and attracts Ir atoms to form ultrasmall\nIr clusters above the cavity to adjust the electronic structure of\nthe Ir clusters. The resulting catalyst Tpyp-Ir(IrO<sub>X</sub>) exhibits\na small overpotential (242 and 259 mV) at a current density of 10\nmA cm<sup>–2</sup> in alkaline and acidic conditions and demonstrates\ngood long-term operational stability. In addition, Tpyp-Ir(IrO<sub>X</sub>) exhibits a higher transition frequency (TOF) (1.69 O<sub>2</sub> s<sup>–1</sup> at 300 mV) in 1 M KOH, which is 7 times\nthat of Ir/C.