Titanium coordination in microporous and mesoporous oxide materials by monochromated X-ray photoelectron spectroscopy and X-ray Auger electron spectroscopy

Abstract

In photoemission, the Auger electron energy, combined with the respective photoelectron energy, provides the so-called Auger parameter α′ which in the case of 3d transition metals, has been demonstrated to be influenced by the coordination state of the emitting atom. In the literature of electron spectroscopy for chemical analysis studies on titanosilicates, the Ti Auger parameter has typically not been reported. In this work, the X-ray photoelectron and the X-ray induced Auger electron spectra of a Ti silicalite (TS-1) and other crystalline mesoporous titanosilicates such as TiSBA-15 and TiMCM-41 have been measured. An α′ value of 882.3 eV, ∼10 eV higher than in TiO 2, has been found for part of the titanium in TS-1 and TiSBA-15 samples. Such a shift in the Auger parameter is attributed to tetrahedral coordination of Ti, substituting for Si atoms in the framework.