Selective hydrogenation of acetylene on Cu–Pd intermetallic compounds and Pd atoms substituted Cu(111) surfaces

Abstract

The selective hydrogenation of acetylene was studied on the ordered Cu–Pd intermetallic compounds (L1₀-type CuPd, L1₂-type Cu₃Pd, and L1₂-type CuPd₃) and Pd-modified Cu(111) surfaces through first-principles calculations. The catalytic selectivity and activity of Cu–Pd alloy catalysts are closely related to the crystal structure and composition of Cu–Pd intermetallic compounds and the size of Pd ensembles of Cu-based dilute alloy surface for the selective hydrogenation of acetylene to ethylene. Significantly, we found that the ordered Cu–Pd alloy surface containing isolated Pd atoms (i.e., L1₂-type Cu₃Pd(111) surface) is highly efficient for the selective hydrogenation reaction of C₂H₂ + H₂ → C₂H₄. The contiguous Pd atom ensembles (Pd dimer and trimer) are catalytically active towards C₂H₂ + H → C₂H₃ and C₂H₃ + H → C₂H₄ reactions than the single Pd atom on a Pd-decorated Cu(111) surface. However, the small Pd ensembles on Cu(111) present a low chemical activity for H₂ dissociation compared with the ordered Cu–Pd intermetallic compounds. Our theoretical results provide a strategy of crystal phase and composition control for enhancing the selectivity and activity of Cu–Pd catalysts towards acetylene selective hydrogenation.