The Role of Electronegative and Electropositive Modifiers in the Adsorption and Decomposition of Acetaldehyde on Rh(111) Surface

Rhodium is an effective catalyst in the CO+H2 reaction into C2-oxygenates. Among the products, acetaldehyde (AA) is an important hydrogen carrier, which is also produced in the decomposition of ethanol on metal surfaces. The chemisorbed acetaldehyde starts to decompose at 200 K. The main products of the chemisorbed AA are CO, H2 and CH4. In the chemisorbed layer η1-(O)-CH3CHOa and η2-(O,C)-CH3CHOa adsorption forms have been identified. Electronegative and electro positive modifiers (oxygen and potassium) suppress the oligomerization of aldehyde, they may influence the stability of these surface complexes such as: (i) surface Ca acts as a simple contaminant by site blocking mechanism. (ii) A direct surface reaction with Oa led to the formation of acetate. (iii) Ka increases the thermal stability of acetaldehyde and the decomposition products by an extended electronic interaction.