PdCx nanocrystals with tunable compositions for alkyne semihydrogenationElectronic supplementary information (ESI) available: Additional TEM, HRTEM, XRD, and catalytic results. See DOI: 10.1039/c8ta12002a

The palladium carbide (PdC x ) material has shown great promise as an efficient catalyst for alkyne semihydrogenation. Difficulties in preparing stable PdC x catalysts have been recognized as the main obstacle. Here, we synthesized a highly stable and durable class of PdC x nanocrystals by treating pre-formed Pd nanocrystals with glucose under hydrothermal conditions. The C/Pd atomic ratios in the resultant PdC x nanocrystals can be varied from 0.04 to 0.18, simply by changing the reaction time. The catalytic results for semihydrogenation of 4-ethynyl-1,1′-biphenyl show that PdC 0.18 nanocrystals exhibit an activity with a turnover frequency as high as 7896 h −1 , ∼7.6 and ∼38 times higher than that of commercial Pd/C and Lindlar catalysts, respectively, as well as a selectivity of >99%. A novel and efficient approach has been reported for the preparation of PdC x nanocatalysts with tunable compositions for enhanced alkyne semihydrogenation.