Recently, we have shown that methane oxidation over Pt/Al2O3 catalysts can proceed via two stable stationary regimes with low and high catalytic activity under identical external conditions. The switching between the regimes occurs abruptly and depends on the oxygen concentration and direction of its change at the constant methane concentration. In situ X-ray photoelectron spectroscopy (XPS) coupled with mass spectrometry was used to correlate changes in the oxidation state of platinum with catalytic activity in the methane oxidation. In situ XPS experiments confirmed the presence of the kinetic hysteresis even at the sub-millibar pressure range (similar to 0.01 mbar). Analysis of the XPS spectra showed that the catalyst activation is associated with partial reduction of the supported platinum. (C) 2016 Elsevier B.V. All rights reserved.