Room-Temperature Hydrogen Adsorption via Spillover in Pt Nanoparticle-Decorated UiO-66 Nanoparticles: Implications for Hydrogen Storage

In order to improve room-temperature hydrogen storage, platinum (Pt) nanoparticles (NPs) are doped onto the Zr-terephthalate metal-organic framework (MOF) UiO-66 and its derivatives for H2 adsorption via spillover effect under a high-pressure environment. Different MOF synthetic modulators are applied for MOF nanoparticle size manipulation, and surface functionality is designed to improve Pt dispersion. Powder X-ray diffraction shows retained MOF integrity after Pt decoration, and the broad Pt peak indicates well-dispersed Pt NPs. The MOF high specific surface areas are slightly reduced after Pt doping with the retained micropore size in the nanometer scale. The hydrogen storage capacity can be improved from 0.08 to 0.71 wt % at 300 K and 30 bar. It is suggested by X-ray photoelectron spectroscopy that the hydrogen capacity enhancement is due to H2 spillover in which spiltover hydrogen radicals hydrogenate carboxylates in MOF supports. Although Pt aggregation reduces H2 capacity in cycles, it is found that MOF and Pt nanoparticle sizes are critical for H2 spillover for subsequent room-temperature hydrogen storage.