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].


References

[1] Th. Dittrich, S. Fengler, “Surface photovoltage analysis of photoactive materials”, World Scientific, 2020.

[2] M. K. Nowotny, et al., „Observation of p-type semiconductivity in titanium dioxide at room temperature”, Materials Letters 64 (2010) 928.

[3] I. Hermann-Geppert, et al., „Cold gas sprayed TiO2-based electrodes for the photo-induced water oxidation”, ECS Transactions 58 (2014) 21.

[4] R. Beranek, et al., „Exploring the electronic structure of nitrogen-modified TiO2 photocatalysts through photocurrent and surface photovoltage studies”, Chem. Phys. 339 (2007) 11.

Branches

Projects

Projects

Company

Company