Dry reforming activity due to ionic Ru in La_1.99Ru_0.01O₃: the role of specific carbonates

Dry reforming of methane was carried out over La_2-2xRu_2xO₃ (x = 0.005, 0.01). Substitution of just 0.5 atom% of Ru in La₂O₃ enhanced the activity by 20 times in terms of conversion when compared to the activity exhibited by La₂O₃. The oxygen storage capacity of the Ru doped sample was considerably higher than undoped La₂O₃, which resulted in higher conversions of CH₄ and CO₂. The measured conversion of CH₄ and CO₂ was 72 and 80%, respectively, at 850 °C. The same was merely 4% with La₂O₃ under the same experimental conditions. DRIFTS studies demonstrated the role of a specific type of carbonates in promoting the activity of the catalyst. DFT calculations provided the rationale behind the selection of the Ru-in-La₂O₃ methane dry reforming catalyst. The surface structures of the pure and Ru-substituted compounds were determined, corroborating the experimental observation of enhanced oxygen storage capacity on Ru substitution. Different active surface oxygen species were identified and their roles in improving reducibilities and improving reactivities were established. The experimentally observed surface carbonate species were also identified using calculations. The combined experiment + calculation approach proved ionic Ru in La_2-2xRu_2xO₃ to be a novel and efficient dry reforming catalyst.