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Defect-Mediated Crystallization of the Particulate TiO2 Photocatalyst Grown by Atomic Layer Deposition
Bela D Bhuskute1, Harri Ali-Löytty2,1, Jesse Saari1
1Surface Science Laboratory, Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 692, FI-33014 Tampere, Finland.
The Journal of Physical Chemistry. C, Nanomaterials and Interfaces
|January 15, 2025
Summary
Titanium dioxide (TiO2) films grown by atomic layer deposition (ALD) on quartz particles exhibit varying photocatalytic activity. Mixed-phase TiO2 demonstrates superior hydrogen production compared to pure anatase TiO2.
Area of Science:
- Materials Science
- Nanotechnology
- Photocatalysis
Background:
- Nanoparticulate oxides are crucial for functionalizing high-surface-area substrates.
- Titanium dioxide (TiO2) is a key material for photocatalytic applications.
- Atomic Layer Deposition (ALD) enables precise thin-film growth on various substrates.
Purpose of the Study:
- To investigate the photocatalytic behavior of TiO2 films deposited by ALD on quartz particles.
- To understand the influence of ALD growth temperature and post-treatment heating rates on TiO2 properties and performance.
- To correlate TiO2 defect structure and phase composition with hydrogen production rates.
Main Methods:
- Amorphous TiO2 thin films (30 nm) were grown using tetrakis(dimethylamido)titanium (TDMAT) via ALD on quartz particles at 100 °C and 200 °C.
- Oxidative heat treatment at 500 °C with variable heating rates was employed for crystallization.
- Characterization of TiO2 defect structure (Ti3+ defects, precursor traces) and phase composition (anatase, rutile) was performed.
- Photocatalytic activity was assessed by measuring hydrogen production rates.
Main Results:
- TiO2 grown at 200 °C exhibited black color due to Ti3+ defects, while TiO2 grown at 100 °C was white with residual TDMAT precursor.
- Oxidative heat treatment led to precursor desorption and oxidation of Ti3+ defects.
- ALD TiO2 grown at 100 °C crystallized as anatase.
- The rutile-to-anatase ratio of TiO2 grown at 200 °C increased with higher heating rates.
- Mixed-phase TiO2 demonstrated a higher hydrogen production rate than pure anatase TiO2.
Conclusions:
- ALD growth temperature significantly impacts the defect structure and subsequent phase formation of TiO2.
- Post-treatment heating rate influences the rutile-to-anatase ratio in TiO2 films.
- Mixed-phase TiO2, achieved through controlled ALD and heat treatment, offers enhanced photocatalytic performance for hydrogen production.
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