Enhancing HT-WGS catalyst performance with stable monovalent copper species via electron supply from defect-induced MgO

Abstract

Magnesium oxide (MgO) exhibits excellent synergy with cerium oxide (CeO2), serving as either textural or electronic promoters during catalytic reactions. However, achieving well-dispersed CeO2-MgO is technically challenging because they are known not to form solid solutions, and the crystal growth of CeO2 suppresses the structure formation of MgO, leading to MgO being in an inhomogeneous amorphous state within CeO2-MgO. For this reason, most of research groups have been struggling with synthesizing well-dispersed CeO2-MgO. This leads them to focusing on the interaction between the active metal and cerium, overlooking the true role of magnesium. In this study, we successfully synthesized well-dispersed CeO2-MgO via a spray pyrolysis-assisted evaporation-induced self-assembly method, followed by the impregnation of Cu. The location and dispersion of Cu nanoparticles were highly dependent on the MgO distribution. Additionally, we revealed that this significantly influenced the catalytic activity and stability towards the HTS reaction and furthermore supplies electrons to monovalent Cu species, helping maintain the stable electron structure and oxidation state of Cu species considered as active sites. These findings suggest that optimizing the MgO distribution in CeO2-MgO is a promising strategy for developing efficient catalysts for the HTS reaction, emphasizing the role of MgO in designing high-performance catalysts.