Breaking the activity-selectivity trade-off for acetylene semihydrogenation by Pd₂ dual-atom site.

Abstract

Acetylene semihydrogenation is a critical process in the polyolefin industry by selectively removing trace acetylene from ethylene-rich reformate. However, this reaction is generally limited by the inherent activity-selectivity trade-off due to the thermodynamic advantage of overhydrogenation. Herein, we develop a facile and straightforward strategy to construct Pd₂ dual-atom sites anchored on defect-rich surface-graphitized nanodiamond (ND@G) via the solvent-mediated dispersion of palladium carboxylate driven by the chelation of palladium precursors via carboxylate anion. Cs-corrected HAADF-STEM images coupled with XAS analysis unambiguously manifest the successful architecting of Pd₂ dual-atom sites. Compared to Pd₁ single-atom sites, the obtained Pd₂/ND@G sample demonstrates superior catalytic performance in acetylene semihydrogenation, with the corresponding TOF values increased from 0.151 s^-1 to 1.953 s^-1, without the obvious decline of ethylene selectivity (93.2%, at full acetylene conversion). C₂H₂/C₂H₄-TPD, H₂-D₂ exchange reaction, isotope-labeled TPSR combined with DFT calculations confirm the effective co-activation of C₂H₂/H₂ on Pd₂ dual-atom sites while maintaining the weak adsorption of ethylene similar to that on its single-atom sites, which can break the activity-selectivity trade-off in acetylene semihydrogenation.