Enhanced Activity of WOx-Promoted PdNi Nanoclusters Confined by Amino-Modified KIT-6 for Dehydrogenation of Additive-Free Formic Acid

Abstract

Formic acid (FA, HCOOH), featured as a major liquid product of biomass processing and especially a liquid sunshine carrier, thus becomes a renewable and promising liquid organic hydrogen carrier. It is highly desirable, but it remains a big challenge to develop a highly active heterogeneous catalyst with no or low content of noble metals for dehydrogenation of additive-free FA at ambient conditions. Herein, for the first time, WOx-modified PdNi alloy nanoclusters immobilized by amino-functionalized KIT-6 (PdNi-WOx/KIT-6-NH2) are prepared through a simple and facile strategy at ambient conditions. PdNi-WOx clusters with an ultrasmall size of 1.4 nm are highly dispersed onto KIT-6-NH2 support. The strong electronic coupling in PdNi-WOx NCs and electronic metal–support interaction between PdNi-WOx NCs and KIT-6-NH2 support lead to the formation of electron-rich PdNi of PdNi-WOx/KIT-6-NH2. The resulting PdNi-WOx/KIT-6-NH2 catalyst exhibits highly efficient catalytic activity and 100% hydrogen selectivity for formic acid dehydrogenation without extra additives, giving turnover frequency (TOF) values of 1699 h–1 at 303 K and 4417 h–1 at 323 K, which is higher than most of the heterogeneous catalysts ever reported. Kinetic isotope effect investigation clearly shows that C–H bond cleavage is the rate-determining step for PdNi-WOx/KIT-6-NH2. This work provides a new insight into designing low-cost and efficient heterogeneous catalysts for dehydrogenation of formic acid.