Suhadolnik Luka, Marinko Živa, Ponikvar-Svet Maja, Tavčar Gašper, Kovač Janez, Čeh Miran
Department for Nanostructured Materials, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
Jožef Stefan International Postgraduate School, Jamova 39, SI-1000 Ljubljana, Slovenia.
J Phys Chem C Nanomater Interfaces. 2020 Feb 20;124(7):4073-4080. doi: 10.1021/acs.jpcc.9b09522. Epub 2020 Jan 21.
TiO nanotubular films prepared using the anodic oxidation process applied to various forms of metal titanium are promising materials for photocatalytic applications. However, during successive anodizations in batch-anodization cells, the chemical composition of the NHF- and water-based ethylene glycol electrolyte changes with each subsequent anodization, which greatly affects the final photocatalytic properties of the annealed TiO nanotubular films. In the present study, 20 titanium discs (Φ 90 mm) were sequentially anodized in the same anodization electrolyte. The chemical composition of the electrolyte was measured after each anodization and correlated with the anodization current density, temperature, electrical conductivity, and pH of the electrolyte and with the morphology, structure, composition, and photocatalytic activity of the resulting TiO nanotube films. It was found that the length of the TiO nanotubes decreased with the age of the electrolyte due to its lower conductivity. The subsurface chemical composition was evaluated by time of flight secondary ion mass spectrometry (ToF SIMS) analyses, and the integrated ToF SIMS signals over a depth of 250 nm for the TiO nanotube films showed that the concentration of F in the annealed TiO film increased with each subsequent anodization due to the increased pH value of the electrolyte. As a consequence, the concentration of the OH and O species decreased, which is a major reason for the reduced photocatalytic activity of the TiO films. It is proposed that the length of the TiO nanotubes does not play a decisive role in determining the photocatalytic activity of the TiO nanotube films. Finally, the best measured degradation results of 60% for caffeine were thus achieved for the first anodized titanium discs. After that the efficiency gradually decreased for each subsequent anodized disc.
通过对各种形式的金属钛进行阳极氧化制备的TiO纳米管薄膜是光催化应用的有前途的材料。然而，在分批阳极氧化槽中进行连续阳极氧化时，基于NHF和水的乙二醇电解质的化学成分在每次后续阳极氧化时都会发生变化，这极大地影响了退火后的TiO纳米管薄膜的最终光催化性能。在本研究中，20个钛盘（Φ 90 mm）在相同的阳极氧化电解质中依次进行阳极氧化。每次阳极氧化后测量电解质的化学成分，并将其与电解质的阳极氧化电流密度、温度、电导率和pH值以及所得TiO纳米管薄膜的形态、结构、组成和光催化活性相关联。发现由于电解质的电导率较低，TiO纳米管的长度随着电解质使用时间的增加而减小。通过飞行时间二次离子质谱（ToF SIMS）分析评估了表面下的化学成分，TiO纳米管薄膜在250 nm深度上的积分ToF SIMS信号表明，由于电解质pH值的增加，退火后的TiO薄膜中F的浓度随着每次后续阳极氧化而增加。因此，OH和O物种的浓度降低，这是TiO薄膜光催化活性降低的主要原因。有人提出，TiO纳米管的长度在决定TiO纳米管薄膜的光催化活性方面不起决定性作用。最后，首次阳极氧化的钛盘对咖啡因的最佳降解率为60%。此后，每个后续阳极氧化盘的效率逐渐降低。
