METAL-CERIA INTERACTIONS AND CATALYTIC ACTIVITY FOR METHANE DISSOCIATION AND CONVERSION

GANDUGLIA-PIROVANO, M. VERÓNICA; LUSTEMBERG, PABLO G.

Ávila

Workshop; NANOSCALE OXIDE SYSTEMS IN PHYSICS AND CHEMISTRY; 2018

The high availability of methane, as well as its climate impact, calls for the development of catalysts for its conversion into commodity chemicals and liquid fuels. Metal-ceria catalysts are promising systems for methane dissociation and conversion. However, the complexity of real (powder) catalysts hinders the fundamental understanding of how they work, which is essential for their rational design. Specifically, the role of ceria in the catalytic activity of ceria-based systems is still not fully understood. To unravel it, well-defined ceria-based model catalysts consisting of metal nanoparticles deposited on a ceria surface are prepared experimentally or created theoretically and investigated. These model catalysts that mimic the real ones in their complexities allow a study of size and support effect. In this talk, recent results on ceria-supported Ni, Co and Cu model catalysts will be discussed, as examples of catalysts for methane dry reforming (DRM: CH4+CO22H2+2CO) [1-3] The emphasis is here put on theoretical studies and special attention is given to the effects of ceria as catalyst support. The ability of ceria to stabilize oxidized species (MOx: Co2+ and Ni2+) on the stoichiometric CeO2 surfaces, by relocalizing electrons on localized f-states, and metallic ones (M0: Co0, Ni0) on the reduced CeO2-x support, is essential for catalytic activity for DRM. Methane dissociation (CH4  CH3  CH2  CH  C) occurs already at room temperature on MOx/CeO2, whereas CO2 dissociation occurs on M0/CeO2-x at the oxygen vacancies formed at higher temperatures (C + Osurf  COgas + Vac). The Co/ceria system is the most active with a barrier for methane dissociation becoming negligible as the MOx /CeO2  M0 /CeO2-x transformation takes place with increasing temperature. Also, the Ni/ceria system is considered for methanol synthesis from methane and water. Water plays a crucial role on C-H Bond breaking and selectivity towards methanol formation; the more water is present, the better.The collaboration with Javier Carrasco, H. Fabio Busnengo, Michael Nolan, Zongyuan Liu, Thomas Duchoň, Vladimír Matolín, Sanjaya D. Senanayake, and Jose A. Rodriguez is gratefully acknowledged.1. Liu, Z.; Grinter, D. C.; Lustemberg, P. G.; Nguyen-Phan, T.-D.; Zhou, Y.; Luo, S.; Waluyo, I.; Crumlin, E. J.; Stacchiola, D. J.; Zhou, J.; Carrasco, J.; Busnengo, H. F.; Ganduglia-Pirovano, M. V.; Senanayake, S. D.; Rodriguez, J. A. Angew. Chem., Int. Ed. 2016, 55, 7455.2. Lustemberg, P. G.; Ramírez, P. J.; Liu, Z.; Gutiérrez, R. A.; Grinter, D. G.; Carrasco, J.; Senanayake, S. D.; Rodriguez, J. A.; Ganduglia-Pirovano, M. V. ACS Catal. 2016, 6, 8184.3. Liu, Z.; Lustemberg, P. G.¸ Gutiérrez, R. A.¸ Carey, J. J.; Palomino, R. M.; Vorokhta, M.; Grinter, D. C.; Ramírez, P. J.; Matolín, V.; Nolan, M.; Ganduglia-Pirovano, M. V.; Senanayake, S. D.; Rodriguez, J. A. Angew. Chem. Int. Ed. 2017, 56, 13041.