Unraveling Surface Chemistry of irreversible reduction of iron oxides through the Time-Resolved APXPS and Chemometrics

Abstract

This work presents a study on the application of Time-Resolved Ambient Pressure X-ray Photoelectron Spectroscopy (TR-APXPS) in association with chemometric techniques, specifically Principal Component Analysis (PCA) and Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS), to investigate the surface chemistry and dynamics of Fe2O3 reduction processes. The use of TR-APXPS allows for real-time monitoring of chemical changes at the surface of Iron oxides during reduction, providing valuable insights into the reaction mechanisms and kinetics involved. One key challenge in analyzing TR-APXPS data is the presence of overlapping peaks and complex spectral features, which can make accurate quantification and interpretation difficult. Traditional spectral fitting methods may struggle with these complexities and result in ambiguous or inaccurate results. However, the chemometric approaches are promising tools to overcome these challenges by extracting pure spectral profiles of individual chemical species and their temporal profiles from the complex and overlapping data. The results obtained from the TR-APXPS coupled with PCA and MCR-ALS analysis provide a detailed and precise understanding of the surface chemical changes during the Fe2O3 reduction. This includes identifying and following the formation of various intermediate species and their evolution over time, which permits later to establish correlations between surface chemistry and process conditions. The integration of both chemometric tools in TR-APXPS data analysis not only addresses the challenges associated with complex spectral features, but also contributes to a deeper understanding of the underlying chemical changes and their dynamics. The obtained results have significant implications for process optimization, material synthesis, and tailoring of material properties for specific applications.