Probe into the effects of surface composition and ensemble effect of active sites on the catalytic performance of C2H2 semi-hydrogenation over the Pd-Ag bimetallic catalysts

Aiming at identifying the effects of surface composition and ensemble effect for the Pd-Ag bimetallic catalysts on the catalytic performance of C2H2 semi-hydrogenation, the selectivity and activity of C2H4 formation over the Ag-doped Pd, Pd-doped Ag catalysts and PdAg intermetallic compounds with different surface composition and ensemble effect are examined utilizing density functional theory calculations. The results indicated that the Pd-Ag bimetallic catalysts without Pd atoms, with isolated Pd atom or Pd dimer on the surface show poor C2H4 selectivity; while those with surface Pd trimer exhibit better C2H4 selectivity, especially, the Pd-doped Ag catalysts present better catalytic performance and low cost. This study not only helps scientists understand reaction theories associated with the experiment of C2H2 semi-hydrogenation over the Pd-Ag bimetallic catalysts, but also helps them advance the design of high-performance, cost-effective and structure-tunable Pd-Ag bimetallic catalysts for C2H2 removal from C2H4, which has broad impact on catalyst development. (C) 2020 Published by Elsevier Ltd.