Enhanced active site extraction from perovskite LaCoO3 using encapsulated PdO for efficient CO2 methanation

Abstract

The extraction of metallic nanoparticles from perovskite-type oxides (ABO3) under mild reducing conditions is a novel way to prepare well-dispersed supported catalysts (B/AOδ). Herein, we found that the encapsulated PdO in perovskite LaCoO3 ([email protected]3) could facilitate the phase transformation of the perovskite structure at a low temperature owing to both strong H2 spillover of Pd and intimate interaction between the encapsulated PdO and LaCoO3. The pure LaCoO3 without PdO was relatively inert to CO2 hydrogenation (CO2 conversion <4%). In contrast, [email protected]3 exhibited excellent CO2 methanation performance with 62.3% CO2 conversion and >99% CH4 selectivity. The characterization results demonstrated that the catalytically active Co2C was in-situ formed by carburization of the extracted Co0 during CO2 methanation for the [email protected]3 sample. Whereas, the LaCoO3 with surface supported PdO (PdO/LaCoO3) showed a weak interaction and remained a perovskite structure with few Co2C active centers after the catalytic reaction, which was similar to the parent LaCoO3. Accordingly, the PdO/LaCoO3 showed an inferior catalytic performance with 31.8% CO2 conversion and 87.4% CH4 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.