Effect of A-site element on the performance of three-dimensionally ordered macroporous manganese-based perovskite catalyst

Development of Ni-doped A-site lanthanides-based perovskite-type oxide catalysts for CO2 methanation by auto-combustion method

Engineering the interfacial interaction between the active metal element and support material is a promising strategy for improving the performance of catalysts toward CO2 methanation. Herein, the Ni-doped rare-earth metal-based A-site substituted perovskite-type oxide catalysts (Ni/AMnO3; A = Sm, La, Nd, Ce, Pr) were synthesized by auto-combustion method, thoroughly characterized, and evaluated for CO2 methanation reaction. The XRD analysis confirmed the perovskite structure and the formation of nano-size particles with crystallite sizes ranging from 18 to 47 nm. The Ni/CeMnO3 catalyst exhibited a higher CO2 conversion rate of 6.6 × 10-5 molCO2 gcat -1 s-1 and high selectivity towards CH4 formation due to the surface composition of the active sites and capability to activate CO2 molecules under redox property adopted associative and dissociative mechanisms. The higher activity of the catalyst could be attributed to the strong metal-support interface, available active sites, surface basicity, and higher surface area. XRD analysis of spent catalysts showed enlarged crystallite size, indicating particle aggregation during the reaction; nevertheless, the cerium-containing catalyst displayed the least increase, demonstrating resilience, structural stability, and potential for CO2 methanation reaction.

Stable and Active Au Catalyst Supported on CeMnO3 Perovskite for Selective Oxidation of Glycerol

The selective oxidation of glycerol holds promise to transform glycerol into value-added chemicals. However, it remains a big challenge to achieve satisfactory selectivity toward the specific product at high conversion due to the multiple reaction pathways. Here, we prepare a hybrid catalyst via supporting Au nanoparticles on CeMnO₃ perovskite with a modest surface area, achieving promoted conversion of glycerol (90.1%) and selectivity of glyceric acid (78.5%), which are much higher than those of CeMnO_x solid-solution-supported Au catalysts with larger surface area and other Ce-based or Mn-based Au catalysts. The strong interaction between Au and CeMnO₃ perovskite facilitates the electron transfer from the B-site metal (Mn) in the CeMnO₃ perovskite to Au and stabilizes Au nanoparticles, which results in the enhanced catalytic activity and stability for glycerol oxidation. Valence band photoemission spectral analysis reveals that the uplifted d-band center of Au/CeMnO₃ promotes the adsorption of the glyceraldehyde intermediate on the catalyst surface, which benefits further oxidation of glyceraldehyde into glyceric acid. The flexibility of the perovskite support provides a promising strategy for the rational design of high-performance glycerol oxidation catalysts.