PdC _x nanocrystals with tunable compositions for alkyne semihydrogenation

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%.