where ∆G 0 is the adsorption energy at θ = 0, α is a positive constant depending on the interactions of the molecules on the surface, and θ refers to the fractional coverage. As explained by Jahanmir and Beltzer 20 the complete form of the Temkin adsorption isotherm is complex and trying to fit several parameters to the HFRR data would result in several possible combinations of α and ∆G 0 . However, at intermediate fractional coverages (0.8 ≥ θ ≥ 0.2) the isotherm takes a simpler form: