Cobalt-doped TiO2: a computational analysis of dopant placement and charge transfer direction on thin film anatase

Abstract

ABSTRACTTitanium dioxide (TiO2) nanocrystals are promising materials for photo-electrochemical water splitting. This study focuses on how surface dopant placement can affect the electronic properties. TiO2 anatase thin films are doped two ways: a cobalt ion replacing a surface titanium ion (surface ingrained) and a cobalt ion chemisorbed to two surface oxygen ions and two NH3 ligands. Specifically, when studying the binding pattern, the cobalt ion dopant changes from an electron acceptor for the surface ingrained model to an electron donor for the chemisorbed model. The optical absorption peaks of the surface ingrained model are attributed to p→d transitions and are much stronger when compared to the d→d transitions for the chemisorbed model. It is the conclusion of this computational study that one can alter the cobalt dopant on the anatase thin film to focus a positive or negative charge at the surface by changing the surface dopant location.