H-Spill storage to maximize the catalytic performances of Pd-based bimetals@Ti3C2Tx MXenes in selective semihydrogenations

Hydrogen spillover is an important theme for hydrogen storage and H-involving catalytic reactions. This work shows that catalytic reactivity and selectivity can be revealed by differentiating the energetic characteristics of spilled H species. With the assistance of Ti, F and C in MXenes, Pd1.8Ni@Ti3C2Tx presents a high capacity for spillover hydrogen storage at ambient temperatures, and the rich oxygenated groups act as the main carriers of hydrogen spillover around metal nanoparticles. Thermodynamic analysis reveals that the catalytic performances are energetically dominated by the adsorption enthalpies of the active spilled H species rather than the amount of spillover hydrogen, and can be tuned by alloying and surface modification. The ideas are verified from the excellent catalysis, chemoselectivity and stereoselectivity of Pd1.8Ni@Ti3C2Tx in semihydrogenations. The strategy of maximizing catalytic performances is applicable to other Pd-based bimetals@Ti3C2Tx, such as Pd2.6Co@Ti3C2Tx and Pd1.5Fe@Ti3C2Tx, and provides new energetics perspectives to understand the catalytic mechanism in spillover-involving chemical procedures.