The enthalpy and entropy values are available in different databases (HSC 6.0 Thermo-chemical
Data Source on PGE [29–37]). The standard Gibbs free energy (DG) values of PGM were calculated
(Table 1, [21–24,35]) as the difference between free energy (G) of the products and reactants (Equation (2)
using data from the NBS tables of chemical thermodynamic properties