| Abstract
| - The electrochemical properties of β-type nickel (oxy)hydroxides Ni(OH)2 and NiO(OH) are known to dependsignificantly on their structural features. In this work, these features are investigated by means of inelasticneutron scattering and infrared and Raman spectroscopies. Our experiments probe both inter- and intramolecular(40−4000 cm-1) vibrational ranges and particular attention is paid to the low-frequency (40−300 cm-1)domain, where new features are observed. Namely, the presence of an IR active mode at around 130 cm-1,characteristic of the oxidized β-NiO(OH) phase, is observed for the first time. The effects of temperature(10−300 K) and deuteration are also measured in order to provide deeper insight into the nature of thevibrational states. A detailed comparison of all of the collected data allows us to propose a new assignmentof the vibrational features observed in both β-Ni(OH)2 and β-NiO(OH) and to quantify the proton dynamicrelevance on the vibrational modes. We show that the interlayer interactions are mostly electrostatic and,hence, do not involve hydrogen bonding. We also point out that, in the oxidized β-phase, protons cannot belocalized so that they can be considered as fully labile. To sum up, this investigation emphasizes that protondelocalization and crystalline disorder, which arise concomitantly upon oxidation, are the key factors thatexplain the evolution of the vibrational features observed between the oxidized and reduced β-type forms.
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