Palladium is of interest as an oxidation catalyst for applications such as methane combustion.
Under the reaction conditions the catalyst may change state from Pd metal to Pd oxide. These changes are accompanied by vast changes in reactivity though it is still debated in the literature as to whether the metal or the oxide is the more reactive phase. At higher oxygen coverages, however, the extremely complex diffraction pattern shown above appears. As the complex diffraction pattern forms, islands and peninsulas are observed to grow on the terraces. This growth is attributed to oxygen penetration into the surface to form a surface with a lower Pd atom density.