Investigation of the surface heterogeneity of solids from reversed-flow inverse gas chromatography

In the present work, the novel methodology of the inverse gas chromatographic technique of reversed-flow gas chromatography (RF-GC) was applied to the well-studied catalytic oxidation of carbon monoxide over silica supported Pt, Rh and Pt–Rh alloy catalysts. Adsorption energies, local isotherms, local monolayer capacities, surface diffusion coefficients, lateral interaction energies and energy distribution functions are simultaneously determined in a single experiment. The variation of the determined physicochemical parameters against the nature of the studied catalysts (Pt content) is consistent with the observed catalytic activity. The energy distribution functions, estimated by means of RF-GC, give useful information about the “ topography” and the nature of the active sites on the catalyst surface, similar to those of experimental techniques, such as Thermal Desorption Spectroscopy studies of the adsorption of CO on group VIII noble metal surfaces. The experimentally found results explain the superior activity of Pt 0.25 + Rh 0.75 alloy, in comparison to that of the pure Pt and Rh catalysts.