Understanding and Optimizing the Sensitization of Anatase Titanium Dioxide Surface with Hematite Clusters

TL;DR

This study uses density functional theory to show that small hematite clusters on anatase TiO2 surfaces enhance photocatalytic activity by improving light absorption and charge transfer, especially at low coverage.

Contribution

It provides a detailed theoretical analysis of how hematite clusters influence TiO2's electronic properties and photocatalytic performance, including effects of oxygen defects.

Findings

Hematite clusters improve TiO2 light absorption and charge transfer.

Low coverage hematite enhances hydrogen evolution reaction.

Oxygen defects significantly alter electronic and magnetic properties.

Abstract

The presence of small hematite (Fe2O3) clusters at low coverage on titanium dioxide (TiO2) surface has been observed to enhance photocatalytic activity, while excess loading of hematite is detrimental. We conduct a comprehensive density functional theory study of Fe2O3 clusters adsorbed on the anatase TiO2 (101) surface to investigate the effect of Fe2O3 on TiO2. Our study shows that TiO2 exhibits improved photocatalytic properties with hematite clusters at low coverage, as evidenced by a systematic study conducted by increasing the number of cluster adsorbates. The adsorption of the clusters generates impurity states in the band gap improving light absorption and consequently affecting the charge transfer dynamics. Furthermore, the presence of hematite clusters enhances the activity of TiO2 in the hydrogen evolution reaction. The Fe valence mixing present in some clusters leads to a significant increase in H2 evolution rate compared with the fixed +3 valence of Fe in hematite. We also investigate the effect of oxygen defects and find extensive modifications in the electronic properties and local magnetism of the TiO2 - Fe2O3 system, demonstrating the wide-ranging effect of oxygen defects in the combined system.