Thermal Ramping Rate during Annealing of TiO2 Nanotubes Greatly Affects Performance of Photoanodes,Physica Status Solidi (A) - Applications and Materials Science

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Thermal Ramping Rate during Annealing of TiO2 Nanotubes Greatly Affects Performance of Photoanodes
Physica Status Solidi (A) - Applications and Materials Science Pub Date : 2021-04-07 , DOI: 10.1002/pssa.202100040
Waseem Raza ₁ , Imgon Hwang ₁ , Nikita Denisov ₁ , Patrik Schmuki _{1,

2,

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Affiliation

Herein, highly ordered TiO₂ nanotube (NT) arrays on a Ti substrate is synthesized in a fluoride-containing electrolyte, using the electrochemical anodization method, which yields amorphous oxide tubes. The effects of different thermal annealing profiles for the crystallization of the amorphous TiO₂ NTs are studied. It is found that the temperature ramping rate has a significant impact on the magnitude of the resulting photocurrents (incident photon-to-current conversion efficiency [IPCE]) from the tubes. No appreciable changes are observed in the crystal structure and morphology of the TiO₂ NTs for different annealing profiles (to a constant temperature of 450 °C). The electrochemical properties of the annealed TiO₂ NTs are investigated using intensity-modulated photocurrent spectroscopy (IMPS), open-circuit potential decay, and Mott–Schottky analysis. The results clearly show that the annealing ramping rate of 1 °C s⁻¹ leads to the highest IPCE performance. This beneficial effect can be ascribed to a most effective charge separation and electron transport (indicating the least amount of trapping states in the tubes). Therefore, the results suggest that controlling the annealing ramping rate is not only a key factor affecting the defect structure but also a powerful tool to tailor the physical properties, and photocurrent activity of TiO₂ NTs.

中文翻译：

TiO2 纳米管退火过程中的热升温速率极大地影响了光阳极的性能

在此，在含氟化物的电解质中，使用电化学阳极氧化方法合成了 Ti 衬底上高度有序的 TiO ₂纳米管 (NT) 阵列，从而产生无定形氧化物管。研究了不同热退火曲线对非晶TiO ₂ NTs结晶的影响。发现温度上升速率对管产生的光电流（入射光子到电流转换效率 [IPCE]）的大小有显着影响。对于不同的退火曲线（450°C 的恒定温度），在 TiO ₂ NTs的晶体结构和形态中没有观察到明显的变化。退火态TiO ₂的电化学性能使用强度调制光电流光谱 (IMPS)、开路电位衰减和莫特-肖特基分析来研究 NTs。结果清楚地表明，1°C s ^-1的退火升温速率导致最高的 IPCE 性能。这种有益效果可以归因于最有效的电荷分离和电子传输（表明管中的俘获态数量最少）。因此，结果表明，控制退火升温速率不仅是影响缺陷结构的关键因素，而且还是调整 TiO ₂ NTs的物理性质和光电流活性的有力工具。

更新日期：2021-04-07

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