| AVS 63rd International Symposium & Exhibition | |
| Applied Surface Science | Monday Sessions |
| Session AS-MoM |
| Session: | Quantitative Surface Analysis: New Ways to Perform Old Tricks |
| Presenter: | Daniel Gaspar, Pacific Northwest National Laboratory |
| Authors: | P. Bhattacharya, University of Dayton Research Institute M.H. Engelhard, Pacific Northwest National Laboratory L. Kovarik, Pacific Northwest National Laboratory L. Estevez, Pacific Northwest National Laboratory Y.-C. Wang, University of Washington D.R. Baer, Pacific Northwest National Laboratory D.G. Castner, University of Washington D.J. Gaspar, Pacific Northwest National Laboratory |
| Correspondent: | Click to Email |
At the nanoscale, quantitatively and accurately measuring material physical and chemical structure remains a fundamental challenge. Many processes essential to energy production or storage, such as catalysis and battery electrochemistry, rely on nanoscale materials with complex three-dimensional structure. In this work, we describe the characterization of ruthenium oxide polyamidoamide (RuOx-PAMAM) dendrimer-encapsulated nanoparticles (DEN) that have been developed as catalysts for lithium-air batteries. In a lithium-air battery, the RuOx-PAMAM DENs catalyze the oxygen evolution reaction during charging. The composition and chemical state of the core nanoparticle, and the three-dimensional structure of the DEN are of great interest in understanding and tuning the performance of these materials in Li-air electrochemical cells. X-ray photoelectron spectroscopy (XPS) has become one of the most widely used tools for surface characterization, including quantitative determination of composition. Accurate XPS quantitation requires accurate understanding of electron escape depth, but this information can, in turn, be used for a more detailed understanding of the distribution of elements with depth in a sample. Rudimentary estimates of the electron escape depth in elemental solids have been supplanted by more accurate methods of accounting for chemical differences in electron escape depth. One such tool is the database developed by Powell, et al., called the NIST Database for Simulation of Electron Spectra for Surface Analysis (SESSA), which allows a user to automatically retrieve data needed for a specific practical application and simulate AES and XPS spectra for a multi-layered thin-film or nanoparticle for measurement conditions specified by the user. This database contains extensive sets of data for the physical quantities relevant to AES and XPS. The internal databases are linked to a user interface via a small expert system that allows a user to automatically retrieve data needed for a specific practical application. SESSA can simulate AES and XPS spectra for a multi-layered thin-film sample for measurement conditions specified by the user. In this work, we have used SESSA to help determine the depth distribution of RuOx and compare to electron microscopy measurements of DEN structure. We have compared the computed model of XPS signal intensity with the experimental measurements.