Study and monitoring of photocatalytic materials (TiO2)

Aim

Photocatalytic materials such as TiO₂ are of great interest, for example, for cleaning of industrial wastewater and for water splitting. The identification of directed charge transfer is important for deeper understanding of the role of defect states, defect bands and doping as well as for technology control.

Solution

SPV spectroscopy in the dc (Kelvin probe, measurement of the contact potential difference, DCPD) and ac (modulated) modes provides information about preferential directed charge separation [1] and allows the investigation of the influence doping on band bending, recombination losses and scavengers (entities accepting electrons or holes) at surfaces.

Application example

It was shown that TiO₂ can be doped n- and p-type by thermal treatment in reducing or oxidizing atmosphere (figure 1, more in [2]). Figure 2 shows the deposition temperature dependence of defect and band gap transitions in TiO₂ after deposition by cold gas spraying of TiO₂ powder (more in [3]). The evolution of defect bands in TiO₂ caused by incorporation, of nitrogen and their effect on charge transfer was studied in [4].