Importance of Exsolution in Transition-Metal (Co, Rh, and Ir)-Doped LaCrO₃ Perovskite Catalysts for Boosting Dry Reforming of CH₄ Using CO₂ for Hydrogen Production

LaCrO₃ perovskite and transition-metal (Co, Rh, Ir)-doped perovskite-based catalysts were fabricated using the Pechini method and applied to the dry reforming reaction of CH₄ using CO₂. One of the prepared perovskite-based catalysts, the LaCr_0.95Ir_0.05O_3- catalyst, showed the highest CH₄ conversion (81%) at 750 °C via the preactivation of the catalyst with H₂ gas. It also showed highly stable catalytic activity for 72 h without coke formation on the catalyst surface. Through X-ray photoelectron spectroscopy and transmission electron microscopy analyses, it is confirmed that the improved catalytic activity of the LaCr_0.95Ir_0.05O_3- perovskite-based catalyst was based on the exsolution of Ir nanoparticles on the catalyst surface, which catalyzes the cleavage of the C-H bond for CH₄. Density functional theory calculations revealed that the exsolution of a dopant Ir in LaCr_0.95Ir_0.05O_3- is more exothermic with/without an oxygen vacancy condition by 1.01 eV/0.43 eV, which suggests the agglomeration of Ir on the surface.