Support effect on methane combustion over iridium catalysts: Unraveling the metal-support interaction mechanism

The redox properties of iridium (Ir) active component are critically important in methane combustion. Interface engineering is highly effective in modulating the redox properties of active metals via tailoring the metal-support interaction (MSI). Herein, Ir catalysts supported on different carriers (TiO₂, CeO₂, Al₂O₃) were synthesized and evaluated for methane combustion. The methane combustion performance varied depending on the support, following the order: Ir/TiO₂ > Ir/CeO₂ > Ir/Al₂O₃ catalysts. Detailed experimental characterizations indicate that, compared with stronger Ir-CeO₂ and Ir-Al₂O₃ interfaces, the unique moderate Ir-TiO₂ interface facilitates the generation of an electron-rich Ir structure with a higher Ir^δ+ ratio. Theoretical simulations further suggest that the initial cleavage of the CH bond in methane molecules is favored at the superior Ir-TiO₂ interface. The more reactive Ir^δ+ species with electron-rich structures in Ir/TiO₂ catalysts not only greatly enhance their redox performance but also lower the activation energy barrier for methane activation, ultimately leading to improved catalytic activity in the total oxidation of methane. This work provides valuable insights for the ingenious catalyst design of more efficient Ir-based catalysts for methane combustion through tailoring MSI.