Effekter av fastfasförändringar vid TiO₂-fotokatalys

Prof. Mats Jonsson Veronica Diesen

The project aims at studying the fundamental chemical processes occurring at the interface between photocatalytically active materials and their surrounding medium.

The issue is relevant for the development of environmentally friendly processes based on photocatalysis for treatment of water whenever it is important not to use chemicals, e.g. for control of microorganisms in the ballast water of ships, for cleansing of natural waters within agriculture, treatment of sewage to eliminate traces of medicines and to protect drinking water from extraneous organisms and chemicals.

Particles in the nanometre range have been found to be the most efficient photocatalytic materials, with titanium dioxide having been identified as the most interesting material due to its otherwise inert and environmentally friendly properties. Photocatalysis occurs in this type of semiconductor materials due to its ability to convert light into a hole-electron pair. This charge separation represents chemical energy which, at the boundary layer, may initiate chemical reactions in the surrounding medium.

The fundamental questions concerning the very rapid reactions and in-between steps that manifest themselves in the initial, transient, chemical stages, show clear parallels with the chemistry occurring when ionising radiation is absorbed in a medium. For example, when ionising radiation affects water the energy is deposited during a very short time (10^ 17 seconds), leading to the formation of hole-electron pairs that relax during a time span ranging from femtoseconds to nanoseconds simultaneously forming very reactive free radicals.

Using radiation chemical methods to study the chemistry of photocatalysis we aim towards enhancing our understanding of the chemistry of photocatalysis through established radiation and electrochemical description models.. This is a way to reduce the complexity of the systems and to hopefully obtain a clearer picture of the fundamental chemistry occurring at the initial stages of photocatalysis.

We expect the knowledge, models and methods developed within the project to be of considerable help in the continued work on developing improved photocatalytic materials for use in engineered systems for process applications of these types of chemical systems.