Selective hydrogenation of acetylene on graphene-supported non-noble metal single-atom catalysts

Large-scale production of polyethylene in industry requires efficient elimination of the trace amount of acetylene impurity. Currently, zeolite adsorption or the conversion of acetylene to ethylene via selective semi-hydrogenation on Pd catalysts is the commonly used method. In this work, we investigate the reaction mechanisms of acetylene hydrogenation on defective graphene (DG) supported single-atom catalysts (SACs), M1/SV-G and M1/DV-G (M=Ni, Pd and Pt) using density functional theory (DFT), where SV-G and DV-G represent DG with single and double vacancies, respectively. It is shown that the metal single-atoms (SAs) as well as their different coordination numbers both affect the activity and selectivity of the hydrogenation process. M1/DV-G provides better H2 dissociation ability than M1/SV-G, which accounts for the poor acetylene hydrogenation activity of M1/SV-G. Based on the reaction barriers, Pt1/DV-G and Ni1/DV-G are better catalysts than other systems considered here, with Ni1/DV-G exhibiting high selectivity for the semi-hydrogenation product of acetylene. These results provide insights for the design of highly selective and noble-metal-free SACs for acetylene hydrogenation on carbon materials.