Photocatalysis : from nanostructured materials to photocatalytic reactors

Catalysis is an important field in chemistry, since 90% of chemical processes involve a catalytic process in at least one of their stages. A study in the USA showed that 60% of the 63 main industrial chemicals are obtained via a process involving a catalysis step, and that 90% of the 34 main industrial processes involve catalysis.

As a result, catalysis is currently the subject of numerous studies. In particular, catalytic processes induced by light activation have been extensively studied in recent decades, as they fit in with current environmental policy aimed at using clean energies, in this case solar energy.

The development of photocatalytic materials efficient under irradiation in the visible range would therefore enable more rational use of solar energy, and thus provide solutions to numerous environmental problems. On earth, the visible part of the solar spectrum represents around 50% of radiation, while ultraviolet (UV) radiation accounts for only around 3-4%.

The development of stable photocatalysts active under irradiation in the visible range is therefore a major challenge. These are generally semiconductors, such as titanium dioxide (TiO ₂ ), whose photocatalytic activity can be extended into the visible range by various modifications or doping. Here, we will present titanium dioxide-based nanostructures and their main synthesis techniques. We will see how titanium dioxide can be doped or surface-modified to extend its range of activity in the visible range. The synthesis of other nanostructured photocatalytic materials (inorganic semiconductors or conjugated polymers) will be presented. The time-resolved microwave conductivity technique enables us to study the dynamics of charge carriers in the irradiated material, which is strongly linked to its photocatalytic activity. The various environmental applications (water and air pollution control, self-cleaning surfaces, hydrogen production) of photocatalytic materials will be described. Finally, we'll look at how these materials can be incorporated into photocatalytic reactors.