Surface structure dependence of selective oxidation of ethanol on faceted CeO₂ nanocrystals

Shaped CeO₂ nanoparticles have been used to explore the effect of surface structure upon the surface chemistry and catalytic selectivity for the ethanol selective oxidation reaction. CeO₂ octahedra, cubes, and rods were synthesized using previously published methods. Adsorption and desorption behavior on these nanoshapes was determined by a combination of temperature-programmed desorption (TPD) and in situ DRIFTS. Activity and selectivity were measured in steady-state reaction and in temperature-programmed surface reaction (TPSR). Shape-dependent differences are observed in surface adsorbates, their transformation temperatures, and the selectivity for dehydration, dehydrogenation, and decomposition. Ethoxide and acetate are the primary surface species present under both TPD and TPSR conditions for all shapes. Different rates of α- and β-CH bond scission on the different shapes are responsible for different product selectivity. Structure-dependent, reductive vacancy formation and availability of reactant O₂ combine to control surface H which in turn plays a role in controlling product selectivity.