Core Shell Prussian Blue Analogue Molecular Magnet Mn-1.5[Cr(CN)(6)]center dot mH(2)O@Ni-1.5[Cr(CN)(6)]center dot nH(2)O for Hydrogen Storage

Abstract

Core-shell Prussian blue analogue molecular magnet Mn-1.5[Cr(CN)(6)]center dot mH(2)O@Ni-1.5[Cr(CN)(6)]center dot nH(2)O has been synthesized using a core of Mn-1.5[Cr(CN)(6)]center dot 7.5H(2)O, surrounded by a shell of Ni-1.5[Cr(CN)(6)]center dot 7.5H(2)O compound. A transmission electron microscopy (TEM) study confirms the core-shell nature of the nanoparticles with an average size of similar to 25 nm. The core-shell nanoparticles are investigated by using x-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and elemental mapping, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and infrared (IR) spectroscopy. The Rietveld refinement of the XRD pattern reveals that the core-shell compound has a face-centered cubic crystal structure with space group Fm3m. The observation of characteristic absorption bands in the range of 2000-2300 cm(-1) in IR spectra corresponds to the CN stretching frequency of Mn-II/Ni-II-N=C-Cr-III sequence, confirming the formation of Prussian blue analogues. Hydrogen absorption isotherm measurements have been used to investigate the kinetics of molecular hydrogen adsorption into core-shell compounds of the Prussian blue analogue at low temperature conditions. Interestingly, the core-shell compound shows an enhancement in the hydrogen capacity (2.0 wt % at 123 K) as compared to bare-core and bare-shell compounds. The hydrogen adsorption capacity has been correlated with the specific surface area and TGA analysis of the core-shell compound. To the best of our knowledge, this is the first report on the hydrogen storage properties of core-shell Prussian blue analogue molecular magnet that could be useful for hydrogen storage applications.