X-ray standing waves (XSW) are used to study redox induced structural and chemical changes to oxide supported monolayer (ML) and nanoparticle (NP) catalysts. Examples include: W / α-Fe2O3(001), V / α-TiO2(110) and Pt / SrTiO3(001). Initial experiments used XSW-excited X-ray fluorescence (XRF) from several hkl Bragg reflections to directly determine the set of Fourier components (phases and amplitudes) of a catalytic species, which were then combined in a Fourier summation to generate a 3D model independent atomic map of the catalytic species. These were complimented by ex situ X-ray photoelectron spectroscopy (XPS) measurements giving the redox induced changes to the chemical state of the catalytic species. More recently we are studying these same types of interfaces with XSW excited XPS to give chemical-state-specificity to the atomic maps of the catalytic species and surface oxygens. For an ALD grown 1 ML MoOx on α-TiO2 (110), the XSW-XPS measured 3D composite atomic maps are shown below for the oxidized and reduced surfaces. DFT calculations show good agreement with these findings and indicate which of the surface oxygens are hydroxyl species.

Atomic-scale view of redox induced changes at the oxide supported monolayer catalyst interface

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.