Interaction of Water with Atomic Layer Deposited Titanium Dioxide on p-Si Photocathode: Modeling of Photoelectrochemical Interfaces in Ultrahigh Vacuum with Cryo-Photoelectron Spectroscopy

This study combines cryo-photoelectron spectroscopy and electrochemical analysis techniques to investigate the p-Si/SiO2/TiO2/H2O system in the context of water-splitting. Atomic layer deposition is used for the preparation of a TiO2 thin film coating for a p-Si/SiO2 photocathode. First, an interface experiment is performed to study the contact properties of the interface between p-Si/SiO2 and TiO2. For the p-Si/TiO2 heterojunction, a downward band bending of 0.3 eV is found for the p-Si toward the interface. Second, a water adsorption experiment is conducted, which allows the investigation of the surface chemistry of the TiO2 coating in contact to water. A direct correlation between the amount of surface hydroxide species, formed due to water dissociation, and Ti3+ defect state density is found. Furthermore, a surface water species can be identified in addition to the commonly found bulk molecular water. Together with the results from a Mott-Schottky analysis, a complete energy level alignment can be constructed.

Automated summary

This study combined cryo-photoelectron spectroscopy and electrochemical analysis techniques to investigate the p-Si/SiO2/TiO2/H2O system in the context of water-splitting. It found a downward band bending for the p-Si/TiO2 heterojunction and a direct correlation between surface hydroxide species and Ti3+ defect state density. Additionally, a surface water species was identified alongside bulk molecular water in contact with the TiO2 coating. The results allowed for a complete energy level alignment construction with Mott-Schottky analysis.