Understanding and optimizing the sensitization of anatase titanium dioxide surface with hematite clusters

The presence of 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 Fe₂O₃clusters adsorbed on the anatase TiO₂(101) surface to investigate the effect of Fe₂O₃on TiO₂. Our study shows that TiO₂exhibits 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 TiO₂in the hydrogen evolution reaction. The Fe valence mixing present in some clusters leads to a significant increase in H₂evolution 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-Fe₂O₃system, demonstrating the wide-ranging effect of oxygen defects in the combined system.