Trace of Atomically Dispersed Pd Enables Unprecedented Butadiene Semihydrogenation Performance Over Copper Catalyst

Semihydrogenation plays a key role in industrial hydrorefining of light alkenes, with a market above 400 billion by 2027. The high cost of commercial palladium-based catalysts strongly calls for innovation but with great challenges. Herein, copper nanoparticles decorated with a minimized ppm of Pd are developed through a chemical plating process to integrate the catalytic advantages of copper and palladium for achieving maximized catalysis in the semihydrogenation of a fatal impurity of butadiene in alkene feedstocks. The developed Pd–Cu catalyst (i.e., 114 ppm of Pd in Pd0.0033Cu1/TiO2) exhibits an unprecedented catalytic performance superior to commercial Pd/Al2O3, with 100% butene selectivity above 90% of butadiene conversion over 130 h on stream at 90 °C. Further exploration reveals that the atomically dispersed Pd on Cu nanoparticles, obtained at ultralow ppm levels of Pd loading, induces a hidden but critical H2 trap, which concentrates H2 on the Pd site for further H2 dissociation that offers intermediate hydrogen atoms to the tandem butadiene semihydrogenation over the third layer of Cu atoms neighboring Pd through hydrogen spillover. Moreover, a threshold on Pd density was identified at Pd/Cu surficial atomic ratio of 1/138 (i.e., Pd0.0033Cu1/TiO2) for maximizing butadiene semihydrogenation performance, based on an extreme collaboration between Pd for H2 dissociation and Cu for butadiene hydrogenation. This work provides important guidance for developing noble metal-saving catalysts in industrial applications.