Simulation of Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements of CO on Supported Pd Nanoparticles

Chi M Yim,Chi L Pang,Geoff Thornton

doi:10.1007/s11244-016-0545-7

Abstract

Near edge X-ray absorption fine structure (NEXAFS) measurements of CO on Pd nanoparticles have been simulated. This was achieved by calculating the CO π* resonance signal of CO on a nanoparticle both as a function of the angle of incidence (I vs θ) and the direction of the electric field vector E of the incident photon beam (I vs β), with the nanoparticle defined as a $$\left( {111} \right)$$ top facet with $$\left\{ {111} \right\}$$ and $$\left\{ {100} \right\}$$ side facets. The dependence of the π* resonance intensity signal of CO covered nanoparticles on the particle geometry and orientation as well as the bond orientation of CO is examined. In addition, we compare our simulations to a set of C K-edge NEXAFS experimental data obtained from a single Pd nanoparticle decorated with CO. Our simulation predicts that the nanoparticle has a high lateral aspect ratio of 37.7 ± 4.1.

Highlights

The study of metal nanoparticles supported on oxide surfaces has become a popular topic of research in recent years
We compare our simulations to a set of C K-edge Near edge X-ray absorption fine structure (NEXAFS) experimental data obtained from a single Pd nanoparticle decorated with CO
In order to study the influence of the particle geometry on the overall I versus h curve, we first define three terms: RTS, RSS, and Rd, where RTS corresponds to the ratio between the number of surface atoms in the (111) top facet and those on the side facets, RSS is the ratio between the number of atoms in the {111}

Summary

Introduction

The study of metal nanoparticles supported on oxide surfaces has become a popular topic of research in recent years. This is motivated in part by their applications in heterogeneous catalysts. To probe molecular adsorbates on nanoparticles, one can use STM to monitor their adsorption sites [7], infrared absorption spectroscopy to investigate their vibrational modes at different sites [8], and microcalorimetry to measure their sticking coefficients as well as adsorption energies on the nanoparticles [9]. To determine molecular orientations on nanoparticles, near-edge X-ray absorption fine structure (NEXAFS) is one of the few experimental tools available

Methods

Results

Conclusion