Enhanced active site extraction from perovskite LaCoO3 using encapsulated PdO for efficient CO2 methanation
The extraction of metallic nanoparticles from perovskite-type oxides (ABO 3 ) under mild reducing conditions is a novel way to prepare well-dispersed supported catalysts (B/AO δ ). Herein, we found that the encapsulated PdO in perovskite LaCoO 3 (PdO@LaCoO 3 ) could facilitate the phase transformation of the perovskite structure at a low temperature owing to both strong H 2 spillover of Pd and intimate interaction between the encapsulated PdO and LaCoO 3 . The pure LaCoO 3 without PdO was relatively inert to CO 2 hydrogenation (CO 2 conversion <4%). In contrast, PdO@LaCoO 3 exhibited excellent CO 2 methanation performance with 62.3% CO 2 conversion and >99% CH 4 selectivity. The characterization results demonstrated that the catalytically active Co 2 C was in-situ formed by carburization of the extracted Co 0 during CO 2 methanation for the PdO@LaCoO 3 sample. Whereas, the LaCoO 3 with surface supported PdO (PdO/LaCoO 3 ) showed a weak interaction and remained a perovskite structure with few Co 2 C active centers after the catalytic reaction, which was similar to the parent LaCoO 3 . Accordingly, the PdO/LaCoO 3 showed an inferior catalytic performance with 31.8% CO 2 conversion and 87.4% CH 4 selectivity. Therefore, the designed encapsulation structure of PdO within perovskite is critical to extract metallic NPs from perovskite-type oxides, which has the potential to prepare other integrated nanocatalysts based on perovskite-type oxides.
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