Theoretical study of hydrogen absorption and desorption in Ti_(1-x)Zr_x Mn_(1.4) using statistical physics treatment: Microscopic investigation and thermodynamic potential interpretation

摘要

Experimental absorption and desorption isotherms of hydrogen in Ti1-xZrx Mn-1.4 (x = 0, 0.1, 0.2, 0.3, 0.4) alloys at T = 293 K have been fitted using some theoretical model expressions treated by statistical physics through the grand canonical ensemble. The monolayer model with two types of sites is used to fit and interpret the experimental data. The physicochemical parameters governing the absorption-desorption processes and included into the model expressions could be numerically deduced from the relevant experimental isotherms. Six parameters of the model are fitted, namely the numbers of hydrogen atoms per site n(1) and n(2), the receptor site densities N-1m and N-2m, and the energetic parameters P-1 and P-2. The evolution of these parameters as function of composition x is plotted and explained in correlation with absorption-desorption processes. Finally, the thermo-dynamic potential functions which govern the sorption mechanisms such as internal energy E-int, free enthalpy of Gibbs G(a) and entropy S-a were derived from statistical physics calculations based on the model adopted. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.