Manganese Dioxides Surface Properties Studied by XPS and Gas Adsorption

Structurally well defined g-MnO2 in terms of Pr and Tw were studied using X-ray photoelectron spectroscopy ~XPS! to complete surface investigations performed by high-resolution gas adsorption, water adsorption, and acid-base surface titration. The O 1s and Mn 2p spectra were deconvoluted into three components Mn-OH2 1 , Mn-OH, and Mn-O2. Analysis of the O 1s spectra in energy shift and relative intensity shows that 70 to 80% of the surface groups stay as neutral OH, 5% as Mn-OH2 and 20 to 30% as Mn-OH: their relative amount varies with Pr as well as PZC, water cross-sectional area and energetic constant C. Mn 2p spectra are far less sensitive than O 1s to the charge variation. Nevertheless a correlation is shown between the relative amount of surface species, the binding energy of Mn 5 O and O 5 Mn species and Tw.