Phase quantification by X-ray photoemission valence band analysis applied to mixed phase TiO₂ powders

Highlights: • XPS valence band spectra are used to quantify surface phase in mixed phase systems. • This is shown to directly link to photocatalytic activity in anatase/rutile TiO₂ mixtures. • The method is applied to known mixtures and P25 powder. • The method may be applied to many other mixed phase systems. - Abstract: A method of quantitative phase analysis using valence band X-ray photoelectron spectra is presented and applied to the analysis of TiO₂ anatase-rutile mixtures. The valence band spectra of pure TiO₂ polymorphs were measured, and these spectral shapes used to fit valence band spectra from mixed phase samples. Given the surface sensitive nature of the technique, this yields a surface phase fraction. Mixed phase samples were prepared from high and low surface area anatase and rutile powders. In the samples studied here, the surface phase fraction of anatase was found to be linearly correlated with photocatalytic activity of the mixed phase samples, even for samples with very different anatase and rutile surface areas. We apply this method to determine the surface phase fraction of P25 powder. This method may be applied to other systems where a surface phase fraction is an important characteristic.