Insights and Activation Energy Surface of the Dehydrogenation of C2HxO Species in Ethanol Oxidation Reaction on Ir(100)

Dehydrogenation of an organic compound is the first and the most fundamental elementary reaction in many organic reactions. In ethanol oxidation reaction (EOR) to form CO2, there are a total of 46 pathways in C2HxO (x=1–6) species leading to the removal of all six hydrogen atoms in five C−H bonds and one O−H bond. To investigate the degree of dehydrogenation in EOR under operando conditions, we performed density function theory (DFT) calculations to study 28 dehydrogenation steps of C2HxO on Ir(100). An activation energy surface was then constructed and compared with that of the C−C bond cleavages to understand the importance of the degree of dehydrogenation in EOR. The results show that there are likely 28 dehydrogenations in EOR under fuel cell temperatures and the last two hydrogens in C2H2O are less likely cleaved. On the other hand, deep dehydrogenation including 45 dehydrogenations can occur under ethanol steam reforming conditions. Activation energy surface of 46 dehydrogenations of C2HxO (x=1–6) species on Ir(100) is constructed from density functional calculations and compared with that of C−C bond cleavage reactions. It is found that 66.7 % dehydrogenation takes place before C−C bond cleavage in ethanol oxidation on Ir(100) under fuel cell temperatures. On the other hand, 100 % dehydrogenation takes place during ethanol oxidation on Ir(100) under ethanol steam reforming.