Visualizing size-dependent dynamics of CeO2-d{100}-supported CoOx nanoparticles under CO2 hydrogenation conditions
Carbon dioxide is a major greenhouse gas. In order to optimize processes focused on its chemical valorization, one needs detailed information about the effects of CO2 and/or CO2/H2 mixtures on the structure and morphology of metal/oxide catalysts. In this study, the evolution of a catalyst with coba...
| Autores: | , , , , , , , |
|---|---|
| Tipo de recurso: | artículo |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/442133 |
| Acceso en línea: | https://hdl.handle.net/2117/442133 https://dx.doi.org/10.1021/jacs.5c04901 |
| Access Level: | acceso abierto |
| Palabra clave: | Catalysts Chemical structure Cobalt Morphology Oxides Catalitzadors Estructura química Àrees temàtiques de la UPC::Enginyeria química::Impacte ambiental |
| Sumario: | Carbon dioxide is a major greenhouse gas. In order to optimize processes focused on its chemical valorization, one needs detailed information about the effects of CO2 and/or CO2/H2 mixtures on the structure and morphology of metal/oxide catalysts. In this study, the evolution of a catalyst with cobalt supported on CeO2-cube nanostructures under CO2 hydrogenation conditions was investigated by using a set of in situ characterization techniques (X-ray absorption fine structure, X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy, and environmental transmission electron microscopy (TEM)). The {100} facets of the ceria support displayed an unexpectedly high stability due to strong interactions with the aggregates of cobalt oxide. A significant influence of interfacial bonding between CoOx and CeO2-d {100} is evident through a clear preference in the orientation of CoOx nanoparticles (NPs) with respect to the substrate. For initially reduced Co/CeO2-cube nanostructures, a kinetically controlled oxidation of cobalt upon the introduction of CO2 was observed during the early stages of CO2 hydrogenation. Environmental TEM revealed the size-dependent morphological behavior of cobalt oxide NPs due to strong interactions with the CeO2 {100} surface. When the environment was switched from H2 to a mixture of H2 and CO2 at 250 °C, small CoOx NPs (in the largest dimension < 2.5 nm) rapidly transformed from a pyramidal three-dimensional (3D) form to a planar, monatomic layer attached to the concurrently oxidized CeO2-d {100} surface. This maximizes the number of sites available for the binding of CO2 or reaction intermediates. The shape transformation reflected the oxophilic character of cobalt and strong metal–support interactions. The removal of CO2 from the gas phase led to a reduction of the cobalt oxide NPs by hydrogen and a reversible two-dimensional ¿ 3D transformation. In contrast, no significant morphological changes, apart from further oxidation, were observed for big CoOx NPs (in the largest dimension > 3 nm). These trends are not seen for nanoparticles of noble metals. The observed morphological and structural changes in the small CoOx NPs affected the stability of reaction intermediates and modified the selectivity of the CoOx/CeO2 catalyst system for methane production. |
|---|