(611f) Shape Effect of the Decomposition of Methanol Over Metal- Doped Ceria

Methanol has been identified as a good source of hydrogen because of its high hydrogen/carbon ratio, safe handling and easy synthesis from renewable and fossil fuels. The decomposition of methanol can be applied to solid oxide fuel cells, operating with both H₂ and CO as fuels in the anode ¹. This process requires the use of a metal such as Cu, Pt, and Pd supported on various oxides. However, our fundamental understanding of the interaction of methanol with the metal and support is still incomplete. From the literature, the difference between VIII and IB group metals in vacuum over single crystals of metal for methanol decomposition reaction is well known ^2-4. Here, we report on the methanol decomposition over metal (Pt, Pd and Au) doped ceria at regular pressures ⁵. At the same time, we investigate the shape effect of ceria on the reaction by considering nanocrystals of ceria prepared with specific exposed planes, such as nanocubes {100}; nanorods {110} and {100}, and nanopolyhedra {111} and {100}.

Nanoscale ceria was synthesized by the hydrothermal method, and the corresponding metal-(Pd, Pt and Au) doped ceria samples were prepared by the deposition/precipitation method. CH₃OH-TPD and CH₃OH (or CH₃OH+H₂O)-TPSR were used to determine reaction onset, reaction intermediates and CO₂ selectivity. The structure of ceria was found to affect the activity. Ceria nanorods facilitate the dispersion and oxidation states of metals on the surface, which was indentified by CO chemisorption and XPS. Moreover, different reaction pathways between Pd, Pt- doped ceria and Au- doped ceria were identified. Product distribution at low temperature showed that over Pd or Pt doped ceria, H₂ and CO are the predominant species; however, for gold doped ceria, methyl formate and H₂ are the main species. This is attributed to the evolution and stability of intermediates (methoxy group). Finally, water was crucial to regenerate the catalyst deactivated during methanol decomposition.

References:

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