Influence of Local Defects on the Dynamics of O-H Bond Breaking and Formation on a Magnetite Surface

TL;DR

This study uses advanced microscopy and computational methods to analyze how local defects on a magnetite surface influence hydrogen atom dynamics, revealing defect-induced variations in diffusion barriers crucial for catalytic processes.

Contribution

It provides new insights into the atomic-scale effects of surface defects on hydrogen diffusion on Fe3O4(001) surfaces using combined experimental and theoretical approaches.

Findings

Hydrogen switches between oxygen atoms at a rate dependent on temperature.

Defects distort the lattice, reducing diffusion paths and altering activation barriers.

Quantitative barrier of approximately 0.94 eV on pristine surfaces was determined.

Abstract

The transport of H adatoms across oxide supports plays an important role in many catalytic reactions. We investigate the dynamics of H/Fe3O4(001) between 295 and 382 K. By scanning tunneling microscopy at frame rates of up to 19.6 fps, we observe the thermally activated switching of H between two O atoms on neighboring Fe rows. This switching rate changes in proximity to a defect, explained by density functional theory as a distortion in the Fe-O lattice shortening the diffusion path. Quantitative analysis yields an apparent activation barrier of 0.94 +/- 0.07 eV on a pristine surface. The present work highlights the importance of local techniques in the study of atomic-scale dynamics at defective surfaces such as oxide supports.