Selective acetylene hydrogenation on Co–Cu(111) surface models: a density functional theory study

The selective semi-hydrogenation of acetylene is a crucial step in the purification of ethylene in petrochemicals industry. Therefore, the design of hydrogenation catalysts with both high activity and high selectivity has important research value. In this study, density functional theory calculations were performed to elucidate how different local Co-Cu surface compositions regulate the adsorption and elementary hydrogenation pathways of acetylene on Cu(111). Four representative surfaces, Cu ML (111), Co 3 Cu 6 (111), Co 6 Cu 3 (111), and Co ML Cu(111), were examined within the same computational framework. On Co 6 Cu 3 (111), the activation barriers for the two desired hydrogenation steps, R1 and R2, were only 0.32 and 0.52 eV, respectively, whereas those for the competing R3 and R4 pathways reached 2.69 and 1.60 eV. Electronic-structure analyses further show that changes in adsorption and reaction energetics are accompanied by redistribution of the adsorbate–metal electronic states and variations in local M-C interactions. These results reveal that Co modification does not produce a simple monotonic promotion of Cu(111); instead, the catalytic response depends strongly on the specific local Co-Cu ensemble formed at the surface. Among the configurations examined, Co 6 Cu 3 (111) provides the most favorable intrinsic kinetic balance between ethylene formation and suppression of competing hydrogenation pathways.