Dynamics of Water in NaxCoO2·yH2O

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• 作者：Niina Jalarvo ; Heloisa N. Bordallo ; Nadir Aliouane ; Mark A. Adams ; Jö ; rg Pieper ; Dimitri N. Argyriou
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：January 24, 2008
• 年：2008
• 卷：112
• 期：3
• 页码：703 - 709
• 全文大小：299K
• 年卷期：v.112,no.3(January 24, 2008)
• ISSN：1520-5207

文摘

Incoherent inelastic neutron scattering experiments were performed on Na_0.7CoO₂ and Na_0.28CoO₂·1.3H₂O inorder to understand how the dynamics of the hydrogen-bond network of water is modified in the triangularcrystalline lattice Na_xCoO₂·yH₂O. Using quasi-elastic neutron scattering (QENS), we were able to differentiatebetween two types of proton dynamics: a fast process (due to water strongly bound into the sodium cobaltoxyhydrate structure during the hydration process) and a slow process (likely attributable to a collectivemotion). High-resolution QENS experiments, carried out on Na_0.28CoO₂·1.3H₂O, show that, at temperaturesabove 310 K, the water dynamics can be well-described by a random jump diffusion model characterized bya diffusion constant equal to 0.9 × 10^-9m²/ s, which is significantly lower than the rate of diffusion for bulkwater. Furthermore, our results indicate that, at room temperature, the sodium ions have no influence on therotational dynamics of the "fast" water molecules.