Homogeneously Distributed Cu-ZnO(-Al<sub>2</sub>O<sub>3</sub>) Nanoparticles Encapsulated with SiO<sub>2</sub> Shells for Superior CO<sub>2</sub> Hydrogenation Activity to Methanol
So Yun Jeong, Ji Hyun Kim, Min Jung Park, Xu Wang, Jong Wook Bae
Abstract
Homogeneously distributed Cu-ZnO(-Al 2 O 3 ) nanoparticles encapsulated with SiO 2 shells (denoted as Cu@Si, CZ@Si, and CZA@Si) are investigated to increase their thermal resistance for stable CO 2 hydrogenation activity caused by the newly formed strong metal–support interaction (SMSI) of spatially confined CZA nanoparticles. The core–shell-structured CZA nanoparticles coated with protective silica shell layers revealed a higher CO 2 hydrogenation activity to methanol with an excellent catalytic stability. The uniformly distributed core–shell-structured CZA nanoparticles ∼3 nm in size were found to be thermally stable even after CO 2 hydrogenation reaction without any structural collapses and insignificant aggregations of the CZA nanoparticles. The spatially confined Cu-based nanoparticles with the help of the SiO 2 protective shell layers having larger strong basic sites (oxygen vacant sites) showed a higher CO 2 conversion of 11.0–15.8% and selectivity to methanol of 46.3–65.4% for a 200 h reaction, which were mainly attributed to their excellent antiaggregation characteristics through SMSI contributions between CZA core nanoparticles and thermally stable protective SiO 2 shell layers.