Chair for Multicomponent Materials

Nanocrack networks: An effective tool to enhance the photocatalytic performance

The sputter-deposited TiO2 film with self-organized nanocrack networks exhibits extremely high photocatalytic activity in comparison to a reference TiO2 thin film (composed of immobilized anatase nanoparticles). Recently, we have shown that TiO2 thin films were deposited from metallic titanium (Ti) target by pulsed DC sputtering method in the presence of argon (process gas) and oxygen (reactive gas). Columnar TiO2 structures were formed due to weak inter-columnar bonding during the sputtering (at high oxygen partial pressures and low deposition rates).

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Fig 1. Scanning electron microscopy (SEM) image of sputter-deposited TiO2 thin film (after the heat treatment).

However, after the heat treatment (650 ℃), oxygen saturated bonds seem to act as a barrier between individual columnar structures and this hinders their coalescence. The absence of strong bonding between individual columns promotes preferential cracking during heating and air quenching cycle and consequently a network of nanoscopic cracks forms. These networks of nanoscopic cracks enhance the overall catalytically active surface area.

Selected publications

A. Vahl, S. Veziroglu, B. Henkel, T. Strunskus, O. Polonskyi, O.C. Aktas, F. Faupel, Pathways to Tailor Photocatalytic Performance of TiO2 Thin Films Deposited by Reactive Magnetron Sputtering, Materials (Basel). 12 (2019) 2840

B. Henkel, T. Neubert, S. Zabel, C. Lamprecht, C. Selhuber-Unkel, K. Rätzke, T. Strunskus, M. Vergöhl, F. Faupel, Photocatalytic properties of titania thin films prepared by sputtering versus evaporation and aging of induced oxygen vacancy defects, Appl. Catal. B Environ. 180 (2016) 362–371

B. Henkel, A. Vahl, O.C. Aktas, T. Strunskus, F. Faupel, Self-organized nanocrack networks: a pathway to enlarge catalytic surface area in sputtered ceramic thin films, showcased for photocatalytic TiO2, Nanotechnology. 29 (2018) 035703