Neutron diffraction and neutron vibrational sectroscopy studies of hydrogen adsorption in the Prussian blue analogue Cu3[Co(CN)6]2

The adsorption of molecular hydrogen in the Prussian blue analogue Cu-3[Co(CN)(6)](2) was investigated using high-resolution neutron powder diffraction and neutron vibrational spectroscopy. Rietveld structural refinement of the neutron data for hydrogen loadings of 1, 2, and similar to 2.3 H-2/Cu showed that the hydrogen was absorbed at two sites within the structure. The most prominent adsorption site, located at the ( (1)/(4), (1)/(4), (1)/(4)) crystallographic site, was an interstitial location within the structure. The second adsorption site was associated with exposed Cu2+ ion coordination sites that result from the presence of [Co(CN)(6)](3-) vacancies within the structure of the material. The rotational-vibrational density of states of the adsorbed hydrogen was probed using neutron vibrational spectroscopy and showed a range of local binding potentials for the adsorbed hydrogen.