Hydrogen Spillover-Accelerated Selective Hydrogenation on WO3 with ppm-Level Pd.

Abstract

Hydrogen spillover from the metal to the support opens a fresh avenue to design dual-active site catalysts for selective hydrogenation. However, very limited knowledge has been obtained to reveal the relationship between the capacity of hydrogen spillover and catalytic performance of hydrogenation. Herein, hydrogen spillover-dependent selective hydrogenation has been demonstrated on WO3-supported ppm-level Pd (PdHD/WO3), where the *H species generated and spilled from Pd to WO3 are readily utilized for addition of a reactant. The WO3 supports with a hexagonal phase and a suitable oxygen defect concentration can enhance the capacity of hydrogen spillover, significantly accelerating the catalytic activity of PdHD/WO3. For the hydrogenation of 4-chloronitrobenzene, the PdHD/WO3 catalysts with the highest capacity of hydrogen spillover yielded a turnover frequency (TOF) of 47,488 h-1 (33 times higher than that of traditional Pd/C). Meanwhile, benefiting from the hydrogen spillover, the unique adsorption of 4-chloronitrobenzene via the nitro group on the oxygen vacancy of WO3 guaranteed >99.9% selectivity of 4-chloroaniline during the whole hydrogenation. This work thus helps to create an effective method for fabricating cost-effective nanocatalysts with an extremely low Pd loading for the ideal hydrogenation with extremely high activity and selectivity.