Models for the Photoelectrolytic Decomposition of Water at Semiconducting Oxide Anodes

摘要

Surface states at semiconducting TiO2/electrolyte interfaces are believed to play an important role in charge transfer and thereby the efficiency of photoelectrochemical processes at such interfaces. Theoretical calculations were therefore performed using the SCF-Xalpha-SW method to determine the position and character of surface states at various characteristic interfaces. At the TiO2/water interface, antibonding surface states were found which when occupied would explain the experimentally observed dissociation of water into hydroxyl groups at n-type semiconducting TiO2 surfaces. Similarly, antibonding surface states were found at the TiO2/OH interface which when occupied would tend to destabilize the OH bond. A likely mechanism for the dissociation of water and decomposition of certain photoanodes in photoelectrochemical cells based on the above results is presented. The effects of surface reconstruction at heavily reduced TiO2 surfaces on the validity of our calculations are also discussed. (Author)