CO2 Hydrogenation Performance of Highly Dispersed Pt and Ru Catalysts Supported on Surface-modified CeO2 Nanostructures.

A. MOLINA; R. NUEZ; S. KHANNYRA; D. GOMA; M.P. YESTE; G. BLANCO; COLLINS, SEBASTIAN; D. MOTTA; M.A. CAUQUI; J.J. CALVINO

Congreso; 15th EuropaCat; 2023

Catalytic hydrogenation using green hydrogen sources is currently explored as a route for the valorization of CO2 into fuels and chemicals. Ceria supported noble metal catalysts stand among systems with potential application in this process, in which both activity and selectivity are influenced by the nature of the metal, their dispersion state and the occurrence of interactions at the metal-ceria interface. Thus, Ru based catalysts seem to favor methanation, whereas those loading Pt directs preferentially the process towards RWGS [1]. In both cases, interaction with Ce3+ species and oxygen vacancies play a major role at this respect [2]. Morphology has proven to largely modify the redox response of ceria nanocrystals, as it is also the case of compositional modifications affecting their first few surface layers. Likewise, the activity of noble metals relates intimately to the atomicity of the species (i.e. isolated atoms, subnanometric clusters or metal nanoparticles). Therefore, controlling these variables offer a possible route to modulate both activity and selectivity issues in this reaction. We have synthesized a series of very low metal loadings (0.1-0.3% wt.) Pt and Ru catalysts highly dispersed onto the surface of ceria nanoxides of different shapes (NanoCubes, NanoRods and NanOctahedra). Furthermore, the redox and acid-base properties of these oxides were modified by mixing Ce with other elements (La, Pr, Zr) at the level of the very first atomic surface layers. Careful characterization of these systems has been undertaken to determine how structure and chemical properties influence performance. Preliminary results point out not only to a large intrinsic activity of the highly dispersed metals but also to a combined contribution of surface crystallography and redox promoters on catalytic performance.