Electrochemical evaluation of thermodynamic parameters for dissolved hydrogen in stoichiometric and nonstoichiometric hydrogen storage alloys

Electrochemical pressure-composition absorption isotherms were measured for stoichiometric and nonstoichiometric Mm(B-5)(x) (Mm=misch metal, B-5=Ni3.6Mn0.4Al0.3Co0.7, 0.88 less than or equal to x less than or equal to 1.12) alloys. Based on the measured isotherms, various thermodynamic parameters were evaluated. Relative chemical potential, enthalpy and entropy of dissolved hydrogen in the Mm(B-5)(x) alloys increased with an increase in x value, while par tial interaction Gibbs energy of dissolved hydrogen decreased, indicating that the dissolved hydrogen atoms in the Mm-poor Mm(B-5)(x) alloys are destabilized and the attractive interaction between the dissolved hydrogen atoms increases. (C) 1997 Elsevier Science S.A.