Self-reduction synthesis of supported ultrafine Pd nanoparticles with high activity and stability in hydrogenation

Supported ultrafine metal nanoparticles display outstanding catalytic performance in heterogeneous catalysis. Nevertheless, there are limited convenient and practical approaches for synthesizing supported ultrafine metal nanoparticle catalysts, despite the development of advanced fabrication methods. High-temperature reduction is often required for the preparation of metal catalysts for catalytic hydrogenation. However, the use of reductants, such as H-2, easily leads to the aggregation of nanoparticles during catalyst preparation. In this work, we developed an effective self-reduction strategy using Pd precursors with organic ligands to prepare supported ultrafine Pd catalysts. Simple calcination under an inert atmosphere leads to the formation of uniform and ultrafine Pd nanoparticles (similar to 1 nm). These Pd precursors were reduced following the reaction between the -CHx groups on ligands and surface hydroxyl species on oxide supports. CO and oxygen vacancies generated in situ both contributed to the stabilization of ultrafine Pd nanoparticles. The as-prepared ultrafine Pd nanoparticles were highly stable even after the high-temperature treatment at 600 degrees C. The catalysts displayed a turnover frequency as high as 26,910 h(-1) for styrene hydrogenation and maintained the catalytic activity for at least 5 test cycles.