Breaking the activity-selectivity trade-off in photocatalytic semihydrogenation of alkynes over palladium nanoparticles with phosphate modification

The Pd-catalyzed semihydrogenation of alkynes to alkenes represents a pivotal industrial process. However, it poses a challenge in balancing activity and selectivity due to the issue of over-hydrogenation. Herein, we develop an efficient photocatalytic approach for the selective semihydrogenation of alkynes with methanol supplying protons powered by visible-light irradiation, which was catalyzed by small-sized Pd nanoparticles supported on SrTiO3 perovskite with surface modification by non-metal phosphate anions. Experimental and theoretical analysis demonstrate that the surface phosphate modification not only enhances light response and the transfer of photogenerated carriers but also regulates the electronic structure and local microenvironment of the active Pd species. Consequently, these results increased generation of active hydrogen species (H*), lowered energy barrier for the rate-determining step, and improved desorption of alkenes. The optimized catalyst, Pd/P-5-SrTiO3, exhibits 1.5 times higher activity in the semihydrogenation of phenylacetylene compared to Pd/SrTiO3 without surface modification. Remarkably, it demonstrates exceptional time-independent selectivity for styrene (>99 %) with excellent stability, effectively overcoming the trade-off between activity and selectivity associated with Pd/SrTiO3. Furthermore, a wide range of alkynes were efficient converted to the corresponding alkenes with high activity and excellent selectivity, highlighting the practical potential of this approach.