A lack of comprehensive studies of the C–C bond cleavage in organic molecules hampers the rational design of catalysts for many applications, such as in fuel cells and steam reforming technologies. Employing ethanol on Ir(100) as an example, we studied 14 C–C bond cleavages of various species involved in the ethanol oxidation reaction using density functional theory calculations and used the degree of dehydrogenation (DoDH) of the reactant species as a variable to correlate the C–C bond cleavage barrier and reaction energy. This correlation method was also applied to the dehydrogenation reactions of ethanol on various catalysts, and great insight was obtained. The results show that the C–C cleavage barrier generally decreases with DoDH, with a local minimum around 33.3% DoDH. For reactants having more than 50% DoDH, the C–C cleavage is more ready to take place than the dehydrogenation and can occur at room temperature. Furthermore, the O atom in the reactive species plays a critical role in lowering the C–C bond cleavage barrier. The results provide necessary inputs for kinetic studies of ethanol reactions under operando conditions, where a reaction network beyond the minimum energy pathway is needed. The results will also serve as a benchmark for future studies of the ethanol C–C cleavage on other facets of Ir catalysts or on different catalysts. Furthermore, this work demonstrates that the proposed method opens up a new and effective way of correlating catalytic activities for the C–C bond cleavage involving long-chain alkanes and alcohols.

Understanding C−C bond cleavages has become important in developing a cost-effective technology for the steam reforming of natural gas, the primary form of hydrogen production. Previous studies of C−C bond cleavages in C 2+ steam reforming have focused solely on the C 2+ H x species. Here, we report the density functional theory (DFT) studies of 10 C−C bond cleavages of ethane decomposition (C 2 H x , x = 0−6) on Ir(100). We also investigated the effects of O and OH species that are present in steam ethane reforming (SER) on these cleavages. The DFT results demonstrate that coupling O with the C 2 H x species decreases activation energy, from >1 to 0.3 eV. Therefore, the C−C bond rupture in SER, along the minimum energy pathway, is likely to take place in C 2 H x O. The findings suggest that a good steam reforming catalyst also needs to facilitate the C 2 H x and O coupling, which would not only improve C−C bond cleavage but also prevent C deposition, a major cause of catalyst deactivation. Furthermore, the activation energy and reaction energy surfaces were constructed for 34 C−C bond cleavage reactions, which allow for direct performance comparisons among catalysts and the selection of a catalyst of interest beyond the minimum energy path.