Effects of Pt particle size on hydrogen storage on Pt-doped metal-organic framework IRMOF-8

A series of Pt-doped IRMOF-8 samples with different Pt catalyst sizes have been prepared via organometallic chemical-vapor deposition (CVD). The Pt catalyst size effects on the spillover storage on IRMOF-8 (or any MOF) were studied for the first time. Our studies showed that the Pt catalyst size is a crucial factor determining whether a significant enhancement in storage can be achieved in the hydrogen spillover system at ambient temperature. Compared to undoped IRMOF-8, the spillover storage capacities on Pt-doped IRMOF-8 samples were enhanced by factors ranging from 1.1 to 1.9 because of different Pt catalyst sizes. The doped Pt size was controlled by varying the CVD conditions to yield mean sizes of 2.2, 3.9, and 9.1 nm, and the results showed that smaller sizes were needed for spillover. Temperature-programmed desorption of dosed H₂/D₂ further shed light on the mechanism of spillover and reverse spillover, confirming undercoordinated sites on the particle-enhanced spillover.