Subsurface chemistry in heterogeneous catalysis plays an important role in tuning catalytic performance. Aiming to unravel the role of subsurface heteroatoms, C2H2 semihydrogenation on a series of Pd catalysts doped with subsurface heteroatom H, B, C, N, P, or S was fully investigated by density functional theory (DFT) calculations together with microkinetic modeling. The obtained results showed that catalytic performance toward C2H2 semihydrogenation was affected significantly by the type and coverage of subsurface heteroatoms. The Pd-B0.5 and Pd-C0.5 catalysts with 1/2 monolayer (ML) heteroatom coverage, as well as Pd-N, Pd-P, and Pd-S catalysts with 1/16 ML heteroatom coverage, were screened to not only obviously improve C2H4 selectivity and activity but also effectively suppress green oil. The essential reason for subsurface heteroatoms in tuning catalytic performance is attributed to the distinctive surface Pd electronic and geometric structures caused by subsurface heteroatoms. In the Pd-B0.5 and Pd-C0.5 catalysts, the Pd surface electronic and geometric effects play the dominant role, while the geometric effect plays a key role in the Pd-N, Pd-P, and Pd-S catalysts. The findings provide theoretically valuable information for designing high-performance metal catalysts in alkyne semihydrogenation through subsurface chemistry.
Keywords: C2H2 semihydrogenation; Pd catalyst; catalytic performance; nonmetallic modifier; subsurface chemistry.