In situ XRD Study of Oscillations during the Methane Oxidation over Palladium and Nickel Foils
Self-sustained oscillations in the methane oxidation over a Pd and Ni foils were studied in situ using time-resolved XRD. Regular oscillations of a relaxation type were observed at the atmospheric pressure in oxygen-deficient conditions in a temperature range of 350–500°C in the case of Pd and in a temperature range of 650-900°C in the case of Ni. During the oscillations the periodic changes of XRD reflex intensities corresponding to Pd, PdO, and “PdCx-like” phases or Ni and NiO phases were accompanied by synchronous variations of the catalyst temperature. The study has clearly confirmed that the originating of oscillations in the catalytic oxidation of methane in both the cases is determined by the periodic oxidation/reduction of the catalyst.