Estimating a Set of Pure XANES Spectra from Multicomponent Chemical Mixtures Using a Transformation Matrix-Based Approach

In this work, we propose a new method for the analysis of time-resolved X-ray absorption near edge structure (XANES) spectra. It allows to decompose an experimental dataset as the product of two matrices: a pure spectral matrix, composed by XANES spectra associable to well-defined chemical species/sites, and their related concentration profiles. This method combines the principal component analysis and the application of a transformation matrix whose elements are directly accessible by the user. We demonstrate the potential of this approach applying it to a series of XANES spectra acquired during the direct conversion of methane to methanol (DMTM) over a Cu-exchanged zeolite characterized by the ferrierite topology. Possibilities and limitations of this methodology are discussed together with a critical comparison with the Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) algorithm that, in the field of X-ray absorption spectroscopy (XAS), is imposing itself as a widely used method for spectral decomposition.