The quantum effect in H2 sorption by mesoporous materials
A.V. Dolbin, M.V. Khlistyuck, V.B. Esel’son, V.G. Gavrilko, N.A. Vinnikov, and R.M. Basnukaeva
B.Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Pr. Nauky, Kharkiv 61103, Ukraine
Received May 11, 2016
The sorption and the desorption of H2 by the mesoporous silicate MCM-41 material have been investigated in the temperature interval 6.8–290 K. It is shown that at T = 60–290 K the thermal activation mechanism is dominant in the kinetics of the sorption of H2 molecules by the MCM-41 sample. Its activation energy was estimated to be Ea ~ 466 K. At T = 17–60 K the diffusion of the H2 molecules in the MCM-41 was practically independent of temperature, which typically occurs when the tunnel mechanism of diffusion dominates over the thermal activation one. The mobility of the H2 molecules in the MCM-41 channels changed at T = 8–17 K which may be indicative of the formation on cooling (or decay on heating) of the monolayer and subsequent H2 layers at the inner surfaces of the channels, its activation energy is Em ~ 21,2 K. Below 8 K the diffusion coefficients of H2 are only slightly dependent on temperature, which may be attributed to the change in mechanism of the channel filling of MCM-41 from layer by layer film formation on the inner surface of the channels to the capillary condensation of H2 molecules. The results of the work were compared with previous data on low-temperature sorption of hydrogen by carbon nanotube bundles.
PACS: 68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation; PACS: 68.43Mn Adsorption kinetics.