Probing the Catalytic Roles of Surface Hydroxyls on Ir/Al 2 O 3 in Dissociation and Dry Reforming of Methane

The synergistic catalysis between the active metal site and the oxide support is crucial for catalytic dry reforming of methane (DRM); however, the specific roles of hydroxyl groups at the metal–oxide interface have been particularly elusive. To probe this, Ir/Al 2 O 3 model catalysts (Ir/Al 2 O 3 -400R and Ir/Al 2 O 3 -650R reduced at 400 and 650 °C, respectively) were constructed with isolated Ir sites but distinct hydroxyl properties. Both catalysts exhibited high activity and coke-resistant stability in long-term DRM reactions at 650 °C. By a combination of structure characterizations, kinetic analyses, and in situ isotopic spectral techniques, their catalytic performances are correlated with the hydroxyl structures. The surface hydroxyls are directly involved in CH 4 and CO 2 dissociation pathways, and specifically, the triply bridged hydroxyl (μ 3 -OH), a strong proton donor, cooperates with the Ir metal site to achieve decoupled CH 4 dissociation. Beyond this synergistic effect, a complete cycle of hydroxyl conversion and regeneration is integral to the DRM mechanism. These findings offer a mechanistic perspective on the catalytic roles of hydroxyls in CH 4 dissociation and dry reforming.