Methane is an extremely important clean fuel source; however, its activation is extremely difficult due to the large energy required to break the first CH bond. This contribution presents a density functional theory investigation of doping of cerium dioxide (111) with (1) alkaline earth metals and (2) divalent Cu and Zn metals to examine their effect in promoting methane activation. The incorporatation of these metal dopants in the surface results in spontaneous formation of charge compensating oxygen vacancies, and also enhances surface reducibility. This effect from substitutional doping of the ceria surface greatly improves the adsorption, and the stablity of the CH<sub>3</sub> + H dissociation products compared to undoped ceria. The enhanced stabilisation of the products drives the thermodynamics towards dissociation. The calculated kinetic barriers show that for the alkaline earths, Mg and Ca doping lower the kinetic barrier compared to the undoped surface, while for Sr the activation energy is higher. Zn substantially lowers the activation barrier, while Cu makes little difference. We examein correlations between the thermodynamics and kinetics and the cation dopant size. Alkaline earth doping shows that the dissociation products become more stable with a larger dopant ionic radius while the kinetic barriers are reduced with increasing cation size up to the limit of the Ca cation. Sr, Cu and Zn appear to show little correlation which we trace to the particular surface structures induced by each dopant. Finally, oxidation of methane on these divalent doped surfaces shows that the dopant can control the selectivity of products, with Zn promoting formaldehyde formation and Mg doping promoting CO2 formation.<br/>Support from the European Commission through the 7th Framework Project BIOGO (www.biogo.eu), grant number 604296, is acknowledged

Insights into methane activation and oxidation on modified ceria catalysts

253rd National Meeting (2017)

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